Final exam

Tree Growth + The Structure of Wood +

Growth occurs by cell division in the cambia zone. The existing bark is pushed outward by the formation of new bark, and the outer bark layers become stretched, cracked, and ridged and are finally sloughed off. ▫

Reinforcing Structural Concrete Slabs

-A concrete slab that spans across parallel beams (one-way action) functions as a very wide beam. -Reinforcing pattern is similar to that of a beam, but with a larger number of smaller top and bottom bars distributed evenly across the width of the slab. -Must provide shrinkage-temperature steel, a set of small-diameter rebars set at right angles, and on top of, the primary reinforcing in the slab. -Function is to prevent cracks from forming parallel to the primary reinforcing because of concrete shrinkage, temperature-induced stresses, or miscellaneous forces that may occur in the building. ▫

Innovations in Sitecast Concrete Construction

-In tilt-up construction, a floor slab is cast on the ground and reinforced concrete wall panels are poured over it in a horizontal position. When curing is complete, the panels are tilted into a vertical orientation and hoisted into position by crane. -Formwork costs are typically less than 5 percent of the cost of the overall concrete system, making it economical for single-story buildings. -Most tilt-up panels are no taller than 45 feet, although panels approaching 100 feet are feasible. -Tilt-up is the most widely used of the innovative construction methods described here.

Casting a Concrete Wall

-Reinforced concrete wall at ground level usually rests on a poured concrete strip footing. -A key, a groove that will form a mechanical connection to the wall, is sometimes formed in the top of the footing. -Vertically projecting dowels of steel rebars are usually installed in the footing before pouring. These overlap with the vertical bars in the walls to form a strong structural connection.

Concrete Construction history

-Romans were the inventors of concrete construction. -Knowledge of concrete construction was lost with the fall of the Roman Empire, not to be regained until the latter part of the 18th century. -In 1824, Joseph Aspdin patented an artificial cement that he named portland cement, after English Portland limestone, whose durability as a building stone was legendary. -Reinforced concrete, in which steel bars are embedded to resist tensile forces, was developed in the 1850s by several people simultaneously. -The combination of steel and concrete did not come into widespread use until a French gardener, Joseph Monier, obtained a patent for reinforced concrete flower pots in 1867. -Monier went on to build concrete water tanks and bridges with the material. -By end of 19th century, engineering design methods had been developed and a number of major structures had been built of reinforced concrete. ▫

Modes of Assembly

-Stick Systems - Unit System - Unit-and-Mullion System - Panel System - Column-Cover-and-Spandrel System

Universal Metal Stud Designators

-The flange width and web depth are expressed in 1/100 inches. -Minimum base metal thickness is expressed in mils (1/1000 inches). Example: 400S137-33 400 = 4" Member depth in 1/100 inches S = Stud or joist sections with flange stiffeners (Cee shapes) 137 = 1 3/8" Flange in 1/100 inches 33 = 33 mil/20 ga = Minimum base metal thickness in mils (0.033 in. = 33 mils) ▫

• Surface Finishes for Aluminum

-Unfinished Aluminum + Oxidation - Anodizing - Fluoropolymer Coatings - Powder Coatings - Baked Enamel Coatings - Applied Surface Effects: Mechanical and Chemical Finishes

Finish Flooring Materials

Concrete Stone Bricks and Brick Pavers Ceramic and Porcelain Tiles Terrazzo Typical Flooring Details: Tile, Brick, Stone, and Terrazzo Wood Flooring Strip flooring T&G Wood Flooring Profiles Plank flooring Engineered Wood Flooring Parquet Floating Floors Wood Flooring -Strip flooring -Most common; solid wood tongue-and-groove material -Typically ¾ inch thick and 1 ½ to 2 ¼ inches wide. -Can be made from many hardwood and softwood species; most common are White oak, Red oak, Pecan, and Maple. -Wood strips are held tightly together and blind nailed by driving nails diagonally through the upper interior corners of the tongues where they are concealed from view once the next strip is installed. -Entire floor is sanded smooth, stained if desired, and finished with a varnish or other clear coating. ▫

Examples of LEED Certified Buildings on UF's Campus

LEEDTM Rating Systems: "Leadership in Energy and Environmental Design" -Most widely adopted systems used in the United States -Established by United States Green Building Council (USGBC) -A number of different rating systems for different types of projects: LEED for New Construction and Major Renovations LEED for Existing Buildings LEED for Commercial Interiors LEED for Core & Shell LEED for Schools LEED for Retail LEED for Healthcare LEED for Homes LEED for Neighborhood Development ▫

Laying Concrete Blocks

Note that mason begins with corners, or leads. As each new course is started on the lead, its height is carefully checked with rule or story pole. ▫

Thermal Insulation of Masonry Walls

Solid masonry wall is a good conductor of heat, which means it is a poor insulator. Three general ways of insulating masonry walls: On the outside face Within the wall On the inside face ▫

Loads on Buildings + Designing for Equilibrium

Three conditions are necessary for a structural system to be in equilibrium: • The sum of all vertical forces = 0. • The sum of all horizontal forces = 0. • The sum of all moments of all forces about any point = 0

The Work of the Design Professional: Choosing Building Systems

Zoning Ordinances -Land Use Regulations -Community and/or Subdivision Covenants Building Codes -Protect public health and safety by setting minimum standards for construction quality, structural integrity, durability, livability, accessibility, and fire safety -Based on one of several model building codes -International Building Code (IBC) is the predominant model code used in the U.S. -States, counties, and municipalities adopt particular model codes with local or regional modifications and/or amendments ▫

sheathing

a facing layer of boards or panels that join and stabilize the pieces into a single structural unit.

Other Group

Includes a variety of less frequently used building stones. Travertine is a relatively rare, partially crystallized, and richly patterned calcite (having a chemistry similar to that of limestone) rock deposited by ancient springs. It is marble-like in its physical qualities. Also included in this group are alabaster, greenstone, schist, serpentine, and soapstone. ▫

Wood Products

Glue-Laminated Wood (glulam) • Three major reasons to laminate: size, shape, and quality. • Individual laminations most commonly 1 ½ inches thick except in curved members with small bending radii, where ¾-inch stock is used. • End joints between individual pieces are either finger jointed or scarf jointed. These allow glue to transmit tensile forces longitudinally from piece to piece.

Masonry Loadbearing Walls

Usually simply called bearing walls. Walls constructed of brick, stone or concrete can be used to support roof and floor structures of light wood framing, heavy timber framing, steel, sitecast concrete, precast concrete, or masonry vaulting. Loadbearing masonry walls can be built with or without reinforcement.

making bricks

1) extracting raw materials 2)preparing the materials 3)shaping the bricks 4)drying 5)firing 6)installation

Stone Masonry: Applications + Patterns

Stone Masonry - stone is laid in mortar, like bricks or concrete blocks, to make walls and vaults - self-supporting (carries its own weight).

Quarrying and Milling of Stone

The construction industry uses stone in many different forms: Fieldstone - is rough building stone obtained from riverbeds and rock-strewn fields Rubble - consists of irregular quarried fragments that have at least one good face to expose in a wall Dimension Stone - quarried and cut into rectangular form Cut Stone - large slabs of dimension stone Ashlar - small rectangular blocks Flagstone - thin slabs of stone, either rectangular or irregular in outline, used for flooring or paving Crushed stone - used in site work and as base layers under buildings Stone dust and powder - used by landscapers for walks, drives, + mulch

• Systems

• A group of interacting, interrelated, or interdependent elements forming a complex whole A group of interacting mechanical or electrical components. • A network of structures and channels, as for communication, travel, or distribution. • An organized set of interrelated ideas or principles. • An organized and coordinated method; a procedure.

Systems Building Terminology closed system open system module modular coordination pre-fabrication

Closed system - components exclusively compatible (often proprietary systems: each piece performs a specific role relative to other components). • Open system - components interchangeable (i.e. wood frame construction). • Module - a geometric convention or material dimension; also used to describe cellular type components or standardized "modular" units. • Modular coordination - dimension-based control system to allow for interface of multiple sub-systems. • Pre-fabrication - pre-assembly of some portion of a building system. ▫

Concrete Masonry materials

Concrete Masonry Units (CMUs) are manufactured in three basic forms: Larger hollow units, commonly referred to as concrete blocks Solid bricks (less common) Larger solid units (least common) Made by vibrating stiff concrete mixture into metal molds for shaping, then turned out onto racks where they are cured at an accelerated rate by subjecting them to steam and sometimes higher pressures to speed curing. Made in a variety of sizes and shapes. Made with different densities of concrete, some of which use cinders (fly ash), pumice (volcanic rock), blast furnace slag, or expanded lightweight aggregates rather than crushed stone or gravel. ▫

Mapping the territory: Stereotomics and Tectonics: Solid and Filigree

Defined in this way, tectonic can be set in opposition to "stereotomic," which involves the cutting and/or carving of solid stone masses. Origin: 1720-30; stereos- ("solid," from Greek) + -tomia ("a cutting of," also from Greek). (2) • Stereotomic and tectonic can be related to the broad categories of solid and filigree construction.

Trusses

Function like beams to transfer loads laterally along their length to supports. • Are made up of a number of separate components working together. • Individual members work in tension or compression (axial forces), with no bending. This works through the triangulation of all members. • In terms of material use versus structural performance, trusses are more efficient than beams. They eliminate mass while retaining structural depth. ▫

Other Types of Masonry Units

Hollow clay tiles - still widely used in other parts of the world but not in U.S. Structural terra cotta - used extensively through the late 19th and early 20th century - have reemerged in facades, particularly as rain screens. (Ch Glass Blocks - hollow (common) and solid (less common) Autoclaved aerated concrete (AAC) - used extensively in Europe - higher insulation value than standard concrete block

Granite,

Igneous rock most commonly quarried for construction in North America. Made up of mineral crystals, principally feldspar and quartz (silica). Nonporous, hard, strong, and durable. The most nearly permanent of building stones, suitable for use in contact with the ground or in locations where it is exposed to severe weathering

Composite Flashing

Laminated, combining multiple layers of various materials. Intermediate in price. Most consist of a heavy foil of copper or lead laminated with polyester film, glass fiber mesh, bitumen-coated fabric, or waterproofed kraft paper. Many composite flashings are very durable. ▫

Marble,

Marble is the second of the major metamorphic stone groups. It is a recrystallized form of limestone. It is easily carved and polished and occurs in white, black, and nearly every color, often with patterns of veining. Properties and appearance vary greatly.

Wood Fasteners + Nails + Nailing Methods

Nails • Common nails + box nails for most structural fastenings • Finish nails less obtrusive + used to fasten finish woodwork • In U.S., size of nail is measured in pennies, abbreviated "d." Originally referred to the price of 100 nails of a given size • Ordinarily furnished bright (plain, uncoated steel) • If exposed to weather, use a corrosion-resistant type, i.e. hot-dip galvanized, aluminum, or stainless steel • Specialty Nails + Machine-Driven Nails • Wood Screws and Lag Screws • Metal Plates • Adhesives ▫

Structural Wood Panels

Plywood • Panels made up of thin layers of wood veneer glued together • Grain on front and back veneers run in long direction of the sheet, whereas the grain in one or more interior crossbands runs perpendicular • Always an odd number of layers in plywood, which equalizes the effects of moisture movement Oriented Strand Board (OSB) - sometimes called waferboard • Made of long shreds (strands) of wood compressed and glued into three to five layers • Strands oriented in same manner in each layer as the grains of the veneer layers in plywood • Stronger and stiffer than other types of nonveneered panels • More economical than plywood

Quartz-Based Dimension Stone,

Sandstone is the second major sedimentary rock type used in building. Found in strongly stratified form or as more homogeneous freestone. Color and physical properties vary significantly with the material that cements the sand particles, which may consist of silica, carbonates of lime, or iron oxide. Quarried principally in New York, Ohio, and Pennsylvania. ▫ Two of the more familiar forms: Brownstone - widely used in wall construction Bluestone - highly stratified and durable stone especially suitable for use in paving and wall copings Will not accept a high polish.

Traditional Project Phases

Schematic design (15%),Design development (25%),construction documentation (40%), bidding(5%), contract administration during construction (15%)

concrete masonry unit sizes

Sizes Concrete Masonry Units (CMUs) are designed to function within a nominal 8-inch module. American standard concrete blocks are nominally 8-inches wide x 8-inches high x 16-inches long shape. Actual dimensions are always 3/8 inch less than nominal dimensions in all directions, to accommodate mortar joints and maintain the 8-inch module. ▫

Slate,

Slate is one of the two metamorphic stone groups used in construction. Slate was formed from clay. It is a dense, hard stone with closely spaced planes of cleavage, along which it is easily split into sheets. Useful for paving stones, roof shingles, and thin wall facings. ▫

Buildings of Layers

Walls, skin, and enclosure must typically perform a number of functions: Express and/or embody formal design intent, the making of inhabited space, and the mediation of interior and exterior, both visually and physically. Structural - gravity (live + dead loads) and/or lateral loads. Thermal resistance - slow movement of heat energy. Moisture resistance - water + water vapor/humidity/moisture. There are few (if any) magic materials that perform all of these functions well. The many different functions are typically addressed through different layers within wall, roof/overhead, and floor assemblies. Each layer is often a different material, addressing the diverse functions of enclosure. The particular way that layers are brought together is an opportunity to impart meaning and intent within the work. ▫

soils

boulders-larger than 3 inches gravel-smaller than 3 inches diameter but larger than #4 sieve sand-smaller than #4 sieve but larger than #200 sieve slits-smaller than 0.02 mm diameter but larger than 0.002 mm diameter clay- smaller than 0.002 mm diameter

Typical Project Organization

owner-architect,contractor- ^ ^ engineer, consultants ^ ^ subcontractors

Sawing Types + Surfacing

plainsawing v. quartersawing plainsawing- produces boards with broad grain figure quartersawing- produces a vertical grain structure, which is seen on the face of the board as tightly spaced parallel summerwood lines

patterns

running bond- simplest pattern which is used in cavity and veneer walls common bond- similar to running bond except for a header course at every 5th 6th and 7th course stack bond- since units do not overlap, longitudinal reinforcements is required in unreinforced walls vertically flemish bond-each course consists of alternating headers and stretchers english bond- pattern consists of alternating stretcher and header courses

Settlement

settlement is due to compression of supporting soil and resulting from a reduction in the volume of its voids

Beams

• A beam transfers its load laterally, or horizontally, along its length to supports. • Beams are subject to bending, which results in a combination of compressive and tensile stresses which are greatest along the beam's top and bottom edges. Beams are also subject to horizontal and vertical shear stresses. • Strength will increase according to the square of its increase in depth

Wood Chemical Treatments

Fire-retardant treatment (FRT) • Preservative-treated wood - where decay or insect resistance is required • Creosote - oily derivative of coal widely used to treat wood in engineering structures; unsuitable for most purposes in building construction • Pressure-treated wood refers to fire-retardant and preservative treatments, since both are typically applied using pressure impregnation processes▫

Detailing Masonry Walls: Flashings and Drainage

Two general types of flashing are used in masonry construction: External flashings - prevent moisture from penetrating into the masonry wall at its exposed top or where it intersects the roof. Internal flashings (also known as concealed or through-wall flashings) - catch water that has penetrated a masonry wall and drain it through weep holes back to the exterior. External flashing at intersection of flat roof and wall parapet is usually constructed in two overlapping parts: Base flashing - often formed by the roof membrane itself. It is normally turned up for a height of at least 8 inches vertically. Counterflashing or Cap Flashing - embedded in the masonry wall above the base flashing and extends downward, lapping over the base flashing. Two parts allow for ease of installation and movement. ▫

Plywood Production

Veneers for plywood are rotary sliced, glued, trimmed to size, sanded, graded, and gradestamped • Unlike structural panels, veneers for interior paneling and cabinetwork are usually sliced from square blocks of wood called flitches • Veneers can be arranged to provide symmetrical grain patterns, if desired (bookmatching)

Decorative Concrete Masonry Units

Also called "architectural concrete masonry units." Wide range of surface patterns, colors, and textures intended for exposed use in exterior or interior walls. Common categories: Split-face units - have an uneven surface, intended to mimic the texture of natural fieldstone. These are used extensively in big-box retail. Sandblasted units - have a light, relatively even and slightly roughened surface. Ground face units - have a smooth polished surface. ▫

• Land Surveys and Descriptions

Boundary Survey - establishes true property corners and property lines of a parcel of land. Typically performed to obtain building permits, to resolve property disputes, and for erecting fences. Easement lines may also be located, if requested, with this type of survey. • Topographic Survey - A Land Survey locating natural and man made features such as buildings, improvements, fences, elevations, land contours, trees, streams, etc. This type of survey may be required by a government agency, or may be used by Engineers and/or Architects for the design of improvements or developments on a site. • Elevation or Floodplain Survey - Elevation surveys determine the elevation of various sections of a building or land. Typically these are used to aid in building plans and to determine if a property is in a flood zone. • Tree Survey - Can show locations, species, and caliper dimensions (diameter) of trees on a site. ▫

Stone Masonry:

Building stone is obtained by taking rock from the earth and reducing it to required shapes and sizes for construction. Natural, richly diverse material that varies in chemistry, structure, physical properties, and appearance. Geologically, stone can be classified into three types according to how it was formed: Igneous Rock - rock that was deposited in a molten state Sedimentary Rock - rock deposited by the action of water and wind Metamorphic Rock - formerly either igneous or sedimentary rock that was then transformed by heat and pressure

Mortar Ingredients

• Most characteristic type is cement-lime mortar, made of portand cement, hydrated lime, an inert aggregate and water. • Portland Cement - the bonding agent in mortar. It is a blend of lime, iron, silica, and alumina. Crushed stone is pulverized and heated in kilns to create dry (dehydrated) powder cement. • Lime - added to mortar to impart smoothness and workability. Produced by burning limestone or seashells (calcium carbonate) in a kiln to drive off carbon dioxide and leave quicklime (calcium oxide). • Aggregate - sand, which must be clean and screened to eliminate particles that are too coarse or too fine. • Water - chemically involved in the curing of the cement and lime. ▫

Concrete Masonry Exterior Bearing Wall with Open-Web Steel Joists

Hybrid System (Filigree + Solid) Structural steel, either light gauge steel or framing steel may be combined depending on the design intentions.▫

Mortar Joint Deterioration

Mortar joints are the weakest link in most masonry walls. Water can accumulate in the joints, where cycles of freezing and thawing weather can gradually spall (split off flakes of) the mortar. Process accelerates and eventually creates water leaks and loosens the masonry units. To forestall this as long as possible: Suitable weather-resistant mortar formulation must be used. Joints must be well filled and tightly compacted with a concave or vee tooling at the time the masonry is laid. After many years of joint deterioration and weathering, masonry walls may require repointing, sometimes called tuckpointing. This is a process of raking and cutting out the defective mortar and replacing it with fresh mortar.

Rights and Responsibilities of Architects in the U.S.

You have the right to practice architecture independently or with others. •You have the responsibility and professional obligation to protect the health, safety, and welfare of building occupants, users, and the public at large. •You are legally responsible for your work. •You can be held professionally liable for errors, omissions, and other deficiencies in the work.

Balloon v. Platform Framing

• Balloon frame was earliest system. Balloon frame used full-length studs that ran continuously for two stories from foundation to roof. Required firestops within wall cavities to prevent vertical spread of fire between stories. • Platform frame is now the universal standard. Wall studs are only one story in height. A floor platform is completed at each level, and the walls bear upon the platform rather than directly upon the walls of the story below.

Mill Construction

• Exterior walls noncombustible • Interior wood construction • Note relationships between roof/floor planking, beams, and girders • Also note pintles, dogs, and uplift anchors ▫

Gypsum Board

-A prefabricated plaster sheet material manufactured in widths of 4 feet and lengths of 8 to 14 feet. -Also known as gypsum wallboard, plasterboard, and drywall ("Sheetrock" is a registered trademark of one manufacturer, and not a generic term). -Least expensive of all interior finishing materials for walls and ceilings. -Retains fire-resistive characteristics of gypsum plaster, but is installed with less labor by less skilled workers than lathers and plasterers. -Installed largely in the form of dry materials, eliminating some of the construction delay that may be associated with curing and drying of plaster

Posttensioning

-Almost exclusively done in place on the building site. -High-strength steel strands called tendons are covered with a steel or plastic tube to prevent them from bonding to the concrete. -Tendons are tensioned after the concrete has cured. -Each tendon is anchored to a steel plate embedded in one end of the beam or slab. -Hydraulic jack is inserted between the other end of the tendon and a similar steel plate on the other end of the member. -ack applies a large tensile force to the tendon while compressing the concrete with an equal but opposite force that is applied through the plate. -Net effect is essentially identical to that of pretensioning. -When process is complete, tendons may be left unbonded or may be bonded by injecting grout to fill the space between the tendons and the tube. ▫

Thermal Breaks

-Aluminum conducts heat rapidly, and requires thermal breaks to prevent condensation and heat movement between interior and exterior. -Thermal breaks are internal components of insulating materials that isolate the aluminum on the interior side of the component from the aluminum on the exterior side. -These are required in aluminum framing members. ▫

Innovations in Sitecast Concrete Construction

-Formwork generally accounts for more than half the cost of site-cast concrete construction. Efforts to reduce this cost have led to new types of formwork panels that are more durable and easily reused multiple times. -Lift-slab construction virtually eliminates formwork. Floor and roof slabs of a building are cast in a stack on the ground, and hydraulic jacks lift the slabs up the columns to their final elevations, where they are welded into place. -Ganged forms are large units made up of a number of panels supported by the same set of walers. Handled by crane and more economical than conventional small panels. -Slip forming is useful for tall-walled structures. A ring of formwork is pulled steadily up by jacks supported on the vertical reinforcing bars. ▫

Concrete Creep

-In addition to plastic and drying shrinkage, concrete is subject to long-term creep. -When placed under sustained compressive stress from its own weight, the weight of other permanent building components, or the force of prestressing, concrete will gradually and permanently shorten over a period of months or years. -Must be accounted for in the design and detailing of building systems, i.e. brick veneer cladding supported on a concrete frame (Allen, Chapter 20). -Horizontal movement joints must be designed into cladding systems to accommodate the differential movements of cladding and structure. -Rule of thumb: sitecast concrete building frames will shorten in height under the influence of their own weight and other dead loads at the rate of 1/16 inch for every 10 feet of building height.

Concrete Flaking, Spalling

-In areas of the country that are subjected to freezing and thawing, the concrete should be air-entrained to resist flaking and spalling of the surface. -The water/cement ratio should be as low as possible to improve durability of the surface. Too much water in the mix will produce a weaker, less durable concrete that will contribute to early flaking and spalling of the surface.

Concrete Flaking, Spalling, and Concrete Cover

-In areas of the country that are subjected to freezing and thawing, the concrete should be air-entrained to resist flaking and spalling of the surface. -The water/cement ratio should be as low as possible to improve durability of the surface. Too much water in the mix will produce a weaker, less durable concrete that will contribute to early flaking and spalling of the surface. -Insufficient concrete cover will lead to corrosion of steel reinforcing, which will also cause the concrete to flake and spall as the steel corrodes. Concrete cover is what protects the reinforcement from fire. Thicker cover will maintain the integrity of the concrete longer in a fire.

Aggregates

-Make up roughly three-quarters of the volume of concrete. -Structural strength is heavily dependent on their quality. -Must be strong, clean, resistant to freeze-thaw deterioration, chemically stable, and properly graded for size distribution. -If dusty or muddy, it will contaminate the cement paste with inert particles that weaken it. -If it contains any number of chemicals from sea salt to organic compounds, it can cause problems ranging from corrosion of reinforcing steel to retardation of the curing process and ultimate weakening of the concrete.▫

One-Way Solid Slab System

-One-way solid slab spans across parallel lines of support furnished by walls and/or beams, and is used for framing of floors and roofs. -Walls and columns are poured prior to erecting the formwork for a one-way slab, but the forms for girders and beams are usually built continuously with those for the slab and they are poured simultaneously as a single piece. -Forms are supported on temporary beams, which in turn are supported on temporary shores (adjustable-length columns). Weight of uncured concrete is enormous, and temporary beams and shoring must be both strong and closely spaced. -Form release agents are applied to formwork. -Reinforcing is placed in forms -Typically 4 to 10 inches deep, depending on span and loading intensit

Open-Web Steel Joists

-Open-web steel joist (OWSJ) is a mass-produced truss used in closely-spaced arrays to support floor and roof decks. -According to Steel Joist Institute (SJI) specifications, produced in three series: -K series joists -spans up to 60 ft; from 8 to 30 inches in depth -LH series joists (Longspan) - spans up to 96 ft; from 18 to 48" in depth -DLH series joists - (Deep Longspan) - spans up to 144 ft; range from 52 to 72" in depth -Most buildings that use open-web joists utilize K series joists less than 2 ft deep to achieve spans of up to 40 ft. -Joist girders - prefabricated steel trusses designed to carry heavy loads, esp. bays of steel joists; can range from 20 to 72 inches deep. ▫

Pouring and Finishing the Slab on Grade

-Pouring/casting of the slab commences with placing concrete in the formwork. -Concrete is spread by workers using shovels or rakes until the form is full, eliminating air pockets in the process. -1st step in finishing the slab is to strike off or screed the concrete by drawing a stiff plank of wood or metal across the top edges of concrete. -2nd step is the initial floating, usually by hand using flat-surfaced bull floats. These flatten and consolidate the surface. -For smoother surface, additional finishing operations proceed after the water sheen on the surface is gone and excess bleed water on the surface has had a chance to evaporate. -When finishing operations complete, slab should be cured under damp conditions for at least a week to prevent surface from cracking.▫

Stick Systems

-Principal components are metal mullions and rectangular panels of glass and spandrel material that are assembled in place on the building. -Advantages of low shipping bulk and high degree of adjustability to unforeseen site conditions. -Disadvantage: must be assembled on-site under highly variable conditions, rather than in a factory with controlled conditions and lower wage rates. -Aluminum entrances and storefronts are also typically installed as stick systems.

Sustainability Considerations

-Raw materials for steel are iron ore, coal, limestone, air and water. -Ore, coal, and limestone are minerals whose mining and quarrying cause disruption of land and loss of wildlife habitat, often coupled with pollution of streams and rivers. -Low-grade iron ore is plentiful, but high-grade iron ore has been depleted in many areas of the earth. -Supplies of some alloying materials, such as manganese, chromium, and nickel are becoming depleted. -Manufacture of one ton (2000 lbs) of steel from iron ore consumes 3170 lbs of ore, 300 lbs of limestone, 900 lbs of coke (made from coal), 80 lbs of oxygen, and 2575 lbs of air (+/- 7025 lbs total raw materials!). -Process releases 4550 lbs of gaseous emissions, and 600 lbs of slag and 50 lbs of dust are generated. ▫ -Embodied energy of steel produced from ore by the basic oxygen process is about 14,000 BTU per pound. Scrap steel is typically added as an ingredient during this process, resulting in recycled content of 25 to 35 percent. -Most structural steel in North America is made from recycled scrap by the electric arc furnace process: Embodied energy is approximately 4000 BTU per pound, less than one-third that of steel made from ore. Recycled content of steel made by this process is 90 percent or higher. -95% or more of all structural steel used in North American building construction is eventually recycled or reused, which is a very high rate -Scrap usually comes from sources within 300 miles of the mill; depending on proximity to site, it can qualify as a local or regional material. ▫

Prestressing and Reinforcing Steel

-Solid slabs, hollow-core slabs, and wall panels are cast around high-strength steel horizontal strands (cables). -Tees, double tees, beams, and girders are often cast around depressed or harped strands for greater structural efficiency of structural action. -Ordinary mild steel reinforcing is also cast into prestressed concrete elements for various purposes: - Beams or slabs that will cantilever are given top reinforcing bars over cantilever points. -Welded wire reinforcing is used to reinforce flanges of tees and double tees, and for general reinforcement of wall panels. -Stirrups, weld plates (connecting devices), and projecting steel loops (used as crane attachments for lifting) are cast into elements. ▫

What is "Sustainability?"

-Sustain: Late 13c., from O.Fr. sustenir "hold up, endure," from L. sustinere "hold up, support, endure," from sub "up from below" + tenere "to hold." 1 -Sustainable: 1610s: "bearable," from sustain + -able. Attested from 1845 in the sense "defensible;" from 1965 with the meaning "capable of being continued at a certain level." Sustainable growth is recorded from 1965. Sustainability dates from 1972 U.N. Conference on Human Development. 1 -U.N. Brundtland Report of 1987: "Sustainable development is development that meets the needs of the present without compromising the ability of future generations to meet their own needs." 2 This is still the most widely used definition for sustainability. -Contemporary use is rooted in social, cultural, and environmental concerns.▫

Steel Alloys

By adjusting the mix of metallic elements used in the production of steel, its strength and other properties can be manipulated. High-strength, low-alloy steels are stronger than mild structural steel Weathering steel: Specified where steel will remain exposed to exterior conditions without a protective finish. Develops a tenacious oxide coating that protects against further corrosion and eliminates need for painting. Stainless steel: Addition of nickel and chromium provides greater corrosion resistance Costs significantly more than conventional structural steel ▫

Types of Masonry Walls

Five Broad Categories or Types of Masonry Walls: Composite Masonry Walls Masonry Cavity Walls Masonry Load-Bearing Walls Reinforced Masonry Walls (vs. unreinforced) Post-Tensioned Masonry Walls Note: These types of walls are not mutually exclusive, and masonry walls are often hybrids between multiple types. ▫

Heavy Timber v. Light Frame Construction

Heavy Timber/Laminated Timber (Lecture 6) • Functions as a structural frame, independent of walls and/or skin • Components larger in dimension ("timber" is more than 5 nom. inches) • Inherently somewhat fire resistive • Specialty connections; connections resist lateral forces • Uses today: Barns, Churches, Custom Residential and/or Institutional Light Frame • Functions as a bearing wall, dependent on walls and skin • Components very small in dimension • More combustible / burns rapidly • Simple connections; shear panels/skins resist lateral forces • Uses today: Residential Construction

Heavy Timber or Mill Construction

Hybrid System (Filigree + Solid) Uses heavy timbers rather than light joists, rafters, and studs. Uses thick timber decking rather than thin wood panel sheathing and subflooring. Because heavy timbers are slower to catch fire and burn than small light frame members, larger floor areas and greater building heights are permitted with Mill Construction than Ordinary Construction. ▫

Insulation Within the Wall

If cavity is wide enough, masons can insert slabs of plastic foam insulation against the inside wythe of masonry as the wall is built. Hollow cores of a concrete block wall can be filled with loose granular insulation or with special molded-to-fit liners of foam plastic. Insulating the cores of concrete blocks does not retard passage of heat through the webs of the blocks, however, and is most effective if coupled with a continuous, unbroken layer of insulation in the cavity or on one face of the wall. ▫

Spanning Systems for Masonry Bearing Wall Condition

Masonry is largely unable to span long horizontal differences (floors + roofs). Often combined with another horizontal system to create a hybrid structure system. Hybrid Systems - 4 Principal variations combined Wood Joist Construction Heavy Timber Steel - Light Gauge and Post + Beam Concrete - Prefabricated and Sitecast

Limestone,

One of the two principal sedimentary rock types used in construction. Found in strongly stratified form or as "freestone" showing little stratification. Colors range from almost white through gray and buff to iron oxide red. Porous, and contains considerable groundwater (quarry sap) when quarried.

Process of Becoming an Architect

Three Typical Requirements: •Education: Compete NAAB-accredited professional architectural degree program (B.Arch or M.Arch). •Experience: Complete Intern Development Program (IDP) through work with a registered architect and/or other approved work settings. •Examination: Complete and Pass the Architecture Registration Examination (ARE). This is a 7-part computerized national examination.

Structures 101

• Loads on Buildings + Designing for Equilibrium • Columns / Beams / Trusses • Rigid Frames and Walls • Rigid Flat Plates and Slabs • Basic Structural Elements • One-way Horizontal Spanning Elements • Lateral Stability • Linear, Planar, and Composite Structural Systems ▫

Softwoods

≈ gymnosperm ≈ evergreen (needles/scales) ≈ structural lumber • Botanically, softwoods are Gymnosperms or conifers; the seeds are naked (not enclosed in the ovary of the flower). • Anatomically, softwoods are nonporous and do not contain vessels. • Softwoods are usually cone-bearing plants with needle- or scale-like evergreen leaves. • Some softwoods, such as larches and bald cypress, lose their needles during autumn or winter. • Major resources of softwood species are spread across the United States, except for the Great Plains where only small areas are forested.

Efflorescence

A fluffy crystalline powder, usually white, that sometimes appears on the surface of a wall of brick, stone, or concrete masonry. Consists of one or more water-soluble salts that were originally present either in the masonry units or in the mortar. Salts were brought to the surface and deposited there by water that seeped into the masonry, dissolved the salts, and then migrated to the surface and evaporated.▫ Can be avoided by: Choosing masonry units that do not contain water-soluble salts Using clean ingredients in the mortar Minimizing water intrusion into the masonry construction ▫

Lumber Grading

Each piece of lumber graded for either appearance or structural strength, depending on intended use. • Lumber grading occurs in the mill. • Lumber is sold by species and grade; the higher the grade, the higher the price. • Structural grading may be done visually or by machine. • Appearance grading is done visually. • Light framing lumber for houses and small buildings is typically ordered as "#2 or better" (a mixture of #1 and #2 grades) for floor joists and roof rafters, and as "Stud" grade for wall framing. • "Economy" grade is reserved for lumber not intended for structural purposes.

Masonry Cavity Walls

Every masonry wall is porous to some degree. A cavity wall prevents water from reaching the interior of a building by creating a hollow space between the inside and outside wythes of the wall. Two wythes are separated by a continuous airspace spanned only by ties made of corrosion-resistant galvanized steel or stainless steel that hold the wythes together. When water penetrates the outer wythe, it is conducted down the cavity and out at the bottom by flashing and drained through weep holes to the exterior of the building. Water-repellent coating, or dampproofing, is applied to the cavity side of the interior wythe of the wall to further protect against water penetration. Board insulation can be added into the cavity to slow the flow of heat through the wall. ▫

Special Problems of Masonry Construction: Expansion and Contraction

Masonry walls expand and contract slightly in response to changes in both temperature and moisture content. New clay (brick) masonry units tend to absorb water and expand under normal atmospheric conditions. New concrete masonry units usually shrink somewhat as they give off excess water following manufacture. Expansion and shrinkage in masonry materials are small compared to the moisture movement in wood or the thermal movement in plastics or aluminum. Must provide surface divider joints to avoid an excessive buildup of forces that could crack or spall the masonry. ▫

Way Horizontal Spanning Elements

These systems are the most commonly used in practice. • Note primary, secondary, and tertiary components operating at different scales: Girder / Beam / Deck or Beam / Joist / Deck • The particular dimensions of joists, beams, and girders vary based on materials and spans, but relationships are consistent.

Anchorage of Timber Beams and Masonry Walls

Three issues to be addressed: • Beam must be protected from decay caused by moisture in masonry walls. Typically addressed by leaving a ventilating airspace of 1/2 inch (13 mm) or more between masonry and beam on all sides except bottom. • Must anchor beam securely so it cannot pull away under normal service • Beam must be able to rotate freely so that it does not pry wall apart if it collapses in a fire. ▫

Wood Shrinkage

When edges of floors and roofs are supported on concrete or masonry, and interiors are supported on wood, there is a possibility for differential shrinkage. • Wood expands and contracts more with changes in moisture content, especially in the direction perpendicular to its grain. • Must detail buildings to minimize effects of differential shrinkage by eliminating cross-grain wood from the interior lines of support. • In traditional mill construction, pintles (steel caps) are used to carry the column loads past the cross-grain of the beams at each floor, so beams and girders can shrink without causing floors and roof to sag. • In contemporary practice, glue-laminated columns may run the full height of the building, with beams connected to columns with wood bearing blocks or welded metal connectors.▫

• Columns

• A column transmits compressive forces vertically along its length. • If the load is centered, the column will simply compress. If the load is offcentered (eccentric) or applied laterally, the column will experience curvature. • The height-to-thickness ratio is known as a column' s slenderness ratio. Tall, slender columns are especially susceptible to buckling unless laterally braced. • The load carrying capacity of a column varies inversely with its height.

mortar

• Serves to cushion the masonry units, giving them full bearing against one another despite their surface irregularities. • Seals spaces between units to keep water and wind from penetrating the wall. • Adheres the units to one another to bond them into a monolithic structural unit. • Important to the appearance of the finished wall. ▫

Casting a Concrete Slab on Grade

-A slab-on-grade is a level surface of concrete that lies directly on the ground. -Unstable topsoil is scraped away to expose subsoil beneath. If exposed topsoil is too soft, it is compacted or replaced with more stable material. -Capillary break - layer of 3/4-inch-diameter crushed stone at least 4-inches deep is compacted over a filter fabric covering the subsoil as a drainage layer to keep water away from underside of slab. -Wood or metal edge forms are installed and coated with form release agent, or compressible joint filler material is placed at perimeter walls to create an isolation joint between slab and surrounding walls. -For interior floor slabs on grade but not exterior slabs, a moisture barrier (or vapor retarder) is laid over the crushed stone to prevent migration of vapor. -Reinforcing mesh of welded wire reinforcing or welded wire fabric is laid over moisture barrier. -Slabs range from 3 inches to 6 or 8 inches, up to a foot for an airport runway.

Making Connections

-Light gauge steel members are usually joined with self-drilling, self-tapping screws, which drill their own holes and form helical threads in the holes as they are driven. Screws are: -Driven rapidly by hand-held electric or pneumatic tools. - Plated with cadmium or zinc to resist corrosion. -Available in assortment of diameters and lengths -Welding is employed to assemble panels of light gauge steel framing that are prefabricated in a factory, and is sometimes used on the jobsite if particularly strong connections are required.

Unit System

-Takes full advantage of factory assembly and minimizes on-site labor. -Units require more space during shipping and more protection from damage than stick system components. ▫

Assembly Concepts for Precast Concrete Buildings

-Three fundamental ways of supporting precast slabs: -Precast concrete skeleton -Precast loadbearing wall panels -Combination skeleton/loadbearing walls -Skeleton may be one bay or many bays deep -Slab elements may be solid, hollow-core, or double tee, topped or untopped -Material is locally manufactured to order and easily customized to an individual building design at minimal additional cost. ▫

Cradle-to-Cradle: William McDonough

Collaboration with Michael Braungart and text from 2002 A broader view based in chemistry and biology Considers materiality in terms of nutrient flows and cyclical relationships between different systems Understand that waste = food

Selecting Interior Finish Systems

Combustibility Combustibility refers to the surface burning characteristics (a material property). -Flame-spread rating indicates rapidness with which fire can spread across a surface of a given material. -Smoke-developed rating classifies a material according to the amount of smoke it gives off when it burns. -Allowable flame-spread and smoke-developed ratings are defined by the building code.

Trends in the Delivery of Design and Construction Services

Improving Collaboration Among Team Members -Integrated Project Delivery (IPD) -Alternative contractual relationships and working arrangements that foster collaboration between project members -Earlier involvement of contractor, construction manager, and trades -Overlapping design and construction phases to reduce "time to market" -Expanded definitions of project services to encompass full life cycle of a project, from conception to occupancy Improving Efficiency in Production: -structure methods of production and supply chain of materials and products to achieve the quickest and most reliable workflow -"Designated Design": metal studs, custom curtain walls, metal fabrications, fabric structures, green roof, etc. via design/build

Outside Glazing and Inside Glazing

Outside glazed -Glass must be installed or replaced by workers standing on scafolding or staging outside the building. -Relatively simple set of shapes that are less expensive for a building that is only one to three stories tall. Inside glazed -Glass is installed or replaced by workers standing inside the building. -More convenient and economical for a tall building. -Requires a somewhat more elaborate set of extrusions. -Some curtain wall systems are designed to allow for glazing from either side.

Hardwoods

≈ angiosperm ≈ deciduous (leaves) ≈ finish carpentry • Botanically, hardwoods are Angiosperms; the seeds are enclosed in the ovary of the flower. • Anatomically, hardwoods are porous; that is, they contain vessel elements. A vessel element is a wood cell with open ends; when vessel elements are set one above another, they form a continuous tube (vessel), which serves as a conduit for transporting water or sap in the tree. • Typically, hardwoods are plants with broad leaves that, with few exceptions in the temperate region, lose their leaves in autumn or winter (deciduous). • Most tropical woods are hardwoods. • Hardwoods occur in all parts of the US, though more grow east of the Great Plains.

History + The Material: Steel

- Prior to beginning of 19th century, steel had little structural role in buildings except in connecting devices. - Metals were rare and expensive materials, produced in small batches for such things as weapons and jewelry. - Greeks + Romans used hidden cramps of bronze to join blocks of stone. - Architects of Renaissance countered thrust of masonry vaults with wrought iron chains + rods. - Cast iron, produced from iron ore in a blast furnace, and wrought iron, iron that has been purified by beating it repeatedly with a hammer, were used for framing industrial buildings in first half of the 19th century. - Limitations - unpredictable brittleness of cast iron and relatively high cost of wrought iron. ▫ - Plentiful, inexpensive steel first became available in the 1850s with the introduction of the Bessemer process: Air was blown into a vessel of molten iron to burn out the impurities. A large batch of iron could be made into steel in about 20 minutes. Structural properties of the resulting metal were vastly superior to those of cast iron. - Open-hearth method was developed in Europe in 1868 and was soon adopted in U.S. - By 1889, when Eiffel Tower was built of wrought iron, several steel frame skyscrapers had already been erected in U.S. ▫

Anodizing

-A manufacturing process that produces an integral oxide coating on aluminum that is thousands of times thicker and more durable than the natural oxide film that would otherwise form. -Acid bath process that takes oxygen from acid and combines it with the aluminum. -May be left clear ("clear anodized") or transparent or opaque color can be added to the coating by dyes, pigments, special electrolytes, or special aluminum alloys. -Advantages of anodized finishes are their extreme hardness and, in most colors, their extreme resistance to weather and fading. -Give an integral appearance with the aluminum surface.▫

Gypsum Plaster

-Abundant mineral. It is quarried, crushed, dried, ground to a fine powder and heated to 350°F in calcining process to drive off ¾ of water of hydration. -Calcined gypsum, ground to a fine white powder, is known as plaster of Paris. -When mixed with water, plaster of Paris rehydrates and recrystallizes rapidly to return to its original solid state. As it hardens, it gives off heat + expands. -Major component of interior finish materials in most buildings. -One major disadvantage: it is soluble in water. -Advantages: inexpensive, highly resistant to fire, durable, light in weight, resists passage of sound better than most materials, has a fine grain, is easily worked in either wet or dry state, and can be fashioned into a number of different surface treatments. -When subjected to fire, thin surface layer of gypsum plaster is calcined and gradually disintegrates. In the process, it absorbs considerable heat and gives off steam. Fire movement through gypsum is slow.

Admixtures

-Air-entraining admixtures increase workability of the wet concrete, reduce freeze-thaw damage, and when used in larger amounts, create very lightweight nonstructural concretes with thermal insulating properties. -Water-reducing admixtures allow a reduction in the amount of mixing water while retaining same workability, which results in a higher-strength concrete. -High-water-reducing admixtures, also known as superplasticizers, transform stiff concrete mix into one that flows freely into forms. Used in difficult circumstances or to reduce the water content to increase strength. -Accelerating admixtures cause concrete to cure more rapidly, and retarding admixtures slow its curing to allow more time for working with the wet concrete. -Workability agents improve plasticity of wet concrete to make it easier to place in forms and finish.▫ -Shrinkage-reducing admixtures reduce drying shrinkage and the cracking that results. -Corrosion inhibitors are used to reduce rusting of reinforcing steel in structures that are exposed to road deicing salts or other corrosion-causing chemicals. -Freeze protection admixtures allow concrete to cure satisfactorily at temperatures as low as 20 °F. -Coloring agents are dyes and pigments used to -alter and control the color of concrete. ▫

Expansion Joints in Metal and Glass Walls

-Aluminum has a relatively high coefficient of thermal expansion; the coefficient of glass is less than half as much. -Because cladding is exposed to air temperature fluctuations as well as direct heating by the sun, it must be provided with expansion joints to allow thermal movement to occur without damaging the cladding or the building frame. -Differential movements are generally accommodated by very small sliding and flexing motions that occur between the glass and the gaskets in which it is mounted. -Rubber blocks placed between edge of glass and mullions on either side prevent the glass from "walking" too far in either direction. -Vertical thermal movement in the aluminum is absorbed by telescoping joints that are provided at regular intervals in the vertical mullions. -Horizontals are interrupted at verticals, providing many joints to absorb horizontal expansion and contraction. ▫

Considerations of Sustainability in Aluminum Cladding

-Aluminum is refined from bauxite ore, which is relatively plentiful. Richest deposits are in tropical areas, where rain forests must be clearcut to facilitate stripmining operations. -Aluminum is refined from bauxite by an electrolytic process that uses huge quantities of electricity. -Large volumes of water are required for smelting. Wastewater from manufacture contains cyanide, antimony, nickel, fluorides, and other pollutants. -Embodied energy of aluminum is roughly 100,000 BTU per pound, seven times that of steel, making it one of the most energy-intensive materials used in construction. -Recycled aluminum is produced using only a fraction of the energy, approximately 5000 BTU per pound.

Aluminum Extrusions

-Aluminum is the metal of choice for metal cladding systems for three primary reasons: -It protects itself against corrosion. -It accepts and holds a variety of attractive surface finishes. -It can be fabricated economically into elaborately detailed shapes by means of the process of extrusion. -Extrusion process is like squeezing toothpaste from a tube.▫

Fabrication and Erection of Reinforcing Bars

-Analogous to other steel fabrication processes: Engineering drawings are sent to contractor/fabricator for shop drawings. Shop drawings are prepared and then reviewed. Shops are used for fabrication of shapes and sizes required, and materials are then delivered to the site for construction. -When put in place, they are typically wired together in forms to await pouring of concrete. -Wires have temporary function only - hold reinforcing in place until concrete cures. -Transfer of load from one rebar to another is done by the concrete. -At splices, bars are overlapped a specified number of bar diameters (typically 30), and loads are transferred through the concrete. -In heavily reinforced columns, there may not be sufficient space to overlap bars, in which case loads are transferred through welds or sleevelike mechanical splicing devices. ▫

Stucco

-Applied over galvanized metal lath, using accessories of galvanized steel. -Gypsum plaster expands during hardening and is highly resistant to cracking. -Portland cement stucco shrinks and is prone to cracking. -Provide control joints at frequent intervals to channel the shrinkage. -Curing reaction is same as that of concrete, and is very slow relative to that of gypsum plaster. -Must be kept moist for at least a week before it is allowed to dry in order to attain maximum hardness and strength. -Usually applied in three coats over metal lath, with a total thickness of 7/8 inch, or in two coats when applied directly to the surface of concrete or concrete masonry, with a thickness of 3/8" to ½". ▫

Construction Process: Fabricator + Erector

-Architects + Structural Engineers -Resolution as structural engineering drawings - Show accurate locations -Shapes and sizes of all members of the frame - All the loads of the members -Do NOT give the exact length to which each member must be cut to mate with the members it joins, and do not give details of the more routine connections of the frame. ▫

One-Way Concrete Joist System (Ribbed Slab) With Joist Bands

-As one-way solid slab spans increase, a progressively thicker slab is required. -Beyond a certain point, the slab becomes so thick that the weight of the slab itself is an excessive burden, unless a substantial portion of the nonworking concrete in the lower part of the slab can be eliminated to reduce weight. -This is the basis for the one-way concrete joist system, also called a ribbed slab. -Bottom steel is concentrated in spaced ribs or joists. -The thin slab that spans across the top of the joists is reinforced only by shrinkage-temperature bars.▫

Curing Concrete

-Because concrete cures by hydration, the chemical bonding of the water and cement, and not by simple drying, it is essential that it be kept moist until its required strength is achieved. -Curing reaction takes place over very long time, but concrete is commonly designed on the basis of the strength it reaches after 28 days. -If it is allowed to dry out at any point during this period, the strength of the resulting concrete will be reduced, and its surface hardness and durability are likely to be adversely affected. -At low temperatures, the curing reaction in concrete proceeds much more slowly. If concrete reaches subfreezing while curing, the reaction stops completely until the temperature rises. It is important to protect concrete from low temperatures. -In very hot temperatures, hydration reaction is accelerated. Use cool ingredients. In extreme conditions, use ice or liquid nitrogen at batch plant.

Bracing + Bridging

-Because light gauge steel members are much more prone to twisting or buckling under load than their wood counterparts, somewhat more attention must be paid to their bracing and bridging. -Studs in tall walls are generally braced at 4-foot intervals. -Steel straps can be screwed to the edges of the studs. -1 1/2-inch cold-formed steel channels can be passed through the punched openings in the studs and welded or screwed to an angle clip at each stud. -Floor joists are bridged with cee-joist blocking between and steel straps screwed to top and bottom edges. -Where large vertical forces must pass through floor joists, steel web stiffeners are screwed to the thin webs of the joists to prevent them from buckling. -Wall bracing consists of diagonal steel straps screwed to the studs.

Making and Placing Concrete

-Begin by establishing desired workability characteristics of the wet concrete and physical properties of the cured concrete. -Given a proper gradation of aggregates, the strength of cured concrete is primarily dependent on the amount of cement in the mix and on the water-cement (w-c) ratio. -For common applications, absolute water-cement ratios range from 0.45 to 0.60 by weight (weight of water in the mix doesn't exceed 45 to 60% of the weight of the portland cement). -More water increases workability but decreases strength. -Most concrete in North America is proportioned at central batch plants, using laboratory equipment to produce concrete of the proper quality. -Concrete is transit mixed en route in a rotating drum on the back of a truck so that it is ready to pour by the time it reaches the job site. -A slump test may be performed at time of pouring to determine if the desired degree of workability has been achieved without making the concrete too wet. -For structural concrete, standard test cylinders are also poured from each truckload. These are taken to testing labs where they are tested for compressive strength. ▫

Joining Precast Concrete Elements

-Bolting, welding, and grouting are all commonly employed. -Connections can be posttensioned to produce continuous beam action at points of support. -Exposed metal connectors not covered by topping are usually dry packed with portland cement grout. Grout is stiff but not actually dry at time it is installed. -Simplest joints are those that rely on gravity by placing one element atop another. -With spanning members, bearing pads are usually inserted at points of contact. These serve to avoid the grinding concrete-to-concrete contact that might create points of high stress + allow for movement caused by expansion and contraction or structural deflection of members. -For resistance to seismic and wind forces, members are tied together laterally. ▫

Stabilizing the Building Frame

-Braced Frame - creates stable triangular configurations, or diagonal bracing, within the otherwise unstable rectilinear geometry of a steel building frame. Connections need not transmit moments (bending forces); they can behave like pins or hinges. -Eccentrically braced frame - ends of diagonal braces are offset some distance from each other allowing structure as a whole to be more resilient. Frame absorbs energy during an earthquake and prevents collapse. -Shear walls - stiff walls made of concrete or reinforced concrete masonry. They function like a braced frame. Moment connections are not required. -Moment-resisting frames - rely on moment connections between beams and columns ▫ -Two common methods of arranging stabilizing elements: -Rigid core - in the center of the building -Structured as a stiff tower, using diagonal bracing, shear walls, or moment connections. -Remainder of building constructed with shear connections and stabilized by the diaphragm action (the rigidity possessed by a thin plate of material such as a welded steel deck with a concrete topping) of the floors and roof that connect these outer bays to the rigid core. -Rigid Perimeter - entire interior can be assembled with shear connections, relying on diaphragm action to impart stability to these portions of the structure. ▫

Masonry Veneer Curtain Walls

-Brick masonry veneer is a single wythe of brick masonry separated by a cavity from a structural backup wall. -Veneer wythe is erected brick by brick or stone by stone with conventional mortar, starting from a steel shelf angle that is attached to the structural frame at each floor. -There must be a soft joint (horizontal expansion joint) beneath each shelf angle -Prevents normal movements in the frame of the building from stressing the masonry veneer. -Allows the veneer to expand and contract without distress. -Must be large enough to absorb the maximum anticipated sum of column creep, brick expansion, spandrel beam deflection, and dimensional tolerances for construction inaccuracies. -Cannot exceed the maximum safe compressibility of the sealant. ▫

Fireproofing of Steel Framing

-Building fires are not hot enough to melt steel, but are often able to weaken it sufficiently to cause structural failure. -Building codes generally limit the use of exposed steel framing to buildings of one to five stories, where escape in case of fire is rapid. -For taller buildings, it is necessary to protect the steel frame from heat long enough for the building to be fully evacuated and the fire extinguished or allowed to burn out on its own. -Fireproofing of steel framing was originally done by encasing steel beams and columns in brick masonry or poured concrete. Added weight. -Search for lighter-weight fire proofing led to many alternatives. ▫

Casting a Concrete Column

-Columns are formed and cast much like a wall, with a few important differences. -Footing is usually an isolated column footing, a pile cap, or a caisson rather than a strip footing. -Dowels are sized and spaced in the footing to match the vertical bars in the column. -Column form may be rectangular box of plywood or composite panels, a cylindrical steel or plastic tube bolted together in halves so that it can later be removed, or a waxed cardboard tube that is stripped after curing by unwinding the layers of paper that make up the tube. ▫

Reinforcing Concrete Columns

-Columns contain two types of reinforcing: -Vertical bars (also called column bars) -Large-diameter reinforcing bars that share the compressive loads with the concrete. -Resist the tensile stresses that occur in columns when a building frame is subjected to wind or earthquake forces. -Arranged either in a circular or rectangular pattern. -Ties -Small-diameter steel wrapped around the vertical bars to help prevent them from buckling under load. -Inward buckling is prevented by the concrete core of the column and outward buckling by the ties. -Two types: column ties (intermittent, more economical + most common) or column spirals (continuous, accordian-type).

Reinforcing

-Concrete has no useful tensile strength. -Structural uses were limited until the concept of steel reinforcing was developed. -Concrete and steel change dimension at nearly the same rate in response to temperature changes. -Steel is protected from corrosion by the alkaline chemistry of concrete. -Concrete bonds strongly to steel, providing a convenient means of adapting brittle concrete to structural elements that must resist not only compression, but tension, shear, and bending as well. -Basic theory of reinforced concrete: put the reinforcing steel where there are tensile forces in a structural member, and let the concrete resist the compression. -Steel is also used to reduce beam depths, in column ties to prevent buckling, and to resist cracking caused by curing shrinkage or thermal expansion. ▫

Cement and Concrete

-Concrete is a rocklike material produced by mixing coarse and fine aggregates, portland cement, and water and allowing the mixture to harden. -Coarse aggregate is normally gravel or crushed stone, and fine aggregate is sand. -Portland cement is a fine gray powder. -During the hardening, or curing, of concrete, the cement combines chemically with water to form strong crystals that bind the aggregates together. This process is called hydration. -During this process, considerable heat, called heat of hydration, is released. -As excess water evaporates from the concrete, it shrinks slightly, a phenomenon referred to as drying shrinkage. -Curing process does not end abruptly, but rather tapers off gradually over long periods of time. -For practical purposes, it is normally considered fully cured after 28 days. ▫

Controlling Cracking in Concrete Slabs on Grade

-Concrete slabs are particularly prone to cracking. -Stresses originate from shrinking that is a normal part of curing process, from thermal expansion and contraction of the slab, or from differential movement between the slab and abutting building elements. -Cracking is managed by introducing an organized system of joints into the slab that allow stresses to be relieved without compromising the appearance or performance of the slab. -Control joints, or contraction joints, are intentionally weakened sections where the tensile forces can be relieved without disfiguring the slab. -Usually formed as groves that extend at least one-quarter depth of slab. -Created via special trowel or by sawing through concrete. -Reinforcing in slab may be partially discontinued where it crosses joints. -Spacing varies based on slab thickness: for slabs 4-8 inches thick, control joints should be spaced between 11 and 17-feet on center -Isolation joints, sometimes called expansion joints -Are formed by casting full-depth preformed joint materials, typically 3/8 to 3/4-inch in width, into the slab. -Completely separate slab from adjacent elements. -Relieve potential stresses by allowing freedom of movement of the slab with respect to other building parts or other portions of the slab. -Commonly provided where the edge of a concrete slab abuts adjacent walls or curbs, as well as around elements, such as columns or loadbearing walls, which pass through the slab within its perimeter. -Used to divide large or irregularly shaped slabs into smaller, more simply shaped rectangular areas that are less prone to stress accumulation

Concrete Stairs

-Concrete stair can be thought of as an inclined one-way solid slab with additional concrete added to make risers and treads. -Underside of formwork is planar. -Concrete is poured in one operation, and the treads are tooled to a steel trowel finish.

Architectural Concrete

-Concrete that is intended as finished interior or exterior surfaces, and is specified with highly prescribed finish characteristics, is known as architectural concrete. -Exposed aggregate finishes involve the scrubbing and hosing of concrete surfaces shortly after the initial set of the concrete to remove the cement paste from the surface and reveal the aggregate. -Chemical retarders are sometimes used to slow the set of the cement paste. These are either sprayed on the surface or used as a coating inside formwork, and can be used selectively to imprint images within the surfaces. -Many formwork options: wood, wood panel products, metal, plastic, and rubber can produce textures that range from glassy smooth to ribbed, veined, board textured, and corrugated. -After curing, texture of concrete can be changed through sandblasting, rubbing with abrasive stones, grinding smooth, and hammering. ▫

Preliminary Design of Steel Structure

-Depth of Steel Beams: 1/20 of their span Example: 40 ft span x 1/20 = 2 ft deep beam -Depth of Steel Girders (girders support beams): 1/15 of their span Example: 45 ft span x 1/15 = 3 ft deep girder -Width of a beam or girder is usually 1/3 to 1/2 of its depth.▫

The Building Life Cycle: Some Questions of Sustainability

-Design for multiple uses over time: -Do the spaces create and/or encourage a certain programmatic "looseness," allowing for multiple different uses to occur over the life of a building? -On construction and the origin of materials used: -Available? Renewable? Recycled content? -Embodied energy - Energy consumed in manufacturing materials or products / transporting materials to site / during construction. -Amount of water used during manufacturing? Wastes generated? -Are there opportunities to reduce/reuse/recycle? -Use and maintenance of the building -Operational Energy - energy use over the building lifetime until demolition. -Water usage? -How much maintenance will be required over time? Labor and materials? - Can the building and materials age gracefully, through weather and use?▫

Sustainability Considerations in Exterior Wall Systems

-Design of the exterior wall has a greater effect on lifetime energy consumption than almost any other factor. -Glass should be used where it can supply daylighting and provide views, but also limited to prevent overheating, glare, or excessive heat loss through the envelope. -Windows that can be opened and closed by the occupants can help reduce energy costs, in some cases. Note humidity issues + cooling/heating lag. -Opaque areas of the exterior wall should be well insulated. -Thermal bridges should be eliminated from the exterior wall. -The entire envelope should be detailed for air-tightness. Fresh air to be provided by building ventilation system, not by air leakage through ext. wall. -South-facing glass can be used to provide solar heat to the building in winter, but must avoid glare, local overheating, + UV deterioration of interiors. -Consider using south-facing surfaces for electrical energy generation

Aggregate Size

-Distribution is important because a range of size grades must be included and properly proportioned in concrete mix to achieve close packing of the particles. -Largest particle in a concrete mix must be small enough to pass easily between the most closely spaced reinforcing bars. -Maximum size should not be greater than three-fourths of the clear spacing between bars or one-third the depth of a slab. -For very thin slabs and toppings, 3/8-inch max. -diameter is often specified. -Maximum of 3/4-inch is common for slab and structural work. -Aggregate diameters up to 6-inches are used in dams and other massive structures. ▫

Precast Concrete Wall Panels

-Either prestressed or conventionally reinforced -Commonly used as loadbearing wall panels -Solid panels range from 3 ½ to 10 inches thick and span one or two stories in height -When prestressed, strands are located in vertical midplane of wall panels to strengthen panels to strengthen panels against buckling and to eliminate camber -Ribbed or hollow-core panels, or sandwich panels with integral rigid insulation, may be as deep as 12 to 24 inches and can span up to four stories ▫

Erector

-Erector is responsible for assembling into a frame on the building site the steel components furnished by the fabricator. -Field welds and bolting are performed on the construction site to join shop-welded and assembled components. -Erector's workers, by tradition, are called ironworkers. -Steel baseplates, which distribute concentrated loads of the steel columns across a larger area, are shop-welded onto columns. -Contractor may provide thin leveling plates set perfectly level at the proper height on a bed of grout atop each concrete foundation. ▫

Framing Procedures

-Essentially the same as that for a building framed with nominal 2-inch wood members. -Framing is usually constructed in platform fashion. -Wall frames are sheathed in either wood panels or gypsum sheathing panels for noncombustible construction. These are similar to gypsum wallboard but with glass mat faces and a water-resistant core formulation. -Light gauge members are designed so they can be nested to form a tubular configuration that is especially strong and stiff. ▫

Plaster over Expanded Metal Lath

-Expanded metal lath is made from thin sheets of steel slit and stretched to produce a mesh of diamond-shaped openings. -Plaster is applied in three coats: -First coat is scratch coat, applied roughly + scratched while still wet using a notched darby, broom, or special rake to create a rough surface. -Second coat is the brown coat, used to build strength, thickness, and to prepare a more level surface. -Third coat is the finish coat. It is a very thin application of finish-coat plaster, about 1/16" thick. -Total thickness of the plaster is +/- 5/8" measured from the face of the lath. -This three-coat system over metal lath is the premium-quality plaster process. -Extremely strong and resistant to fire. -Disadvantage: cost, largely attributed to labor involved. ▫

Types of Ceilings

-Exposed structural and mechanical components (no finished ceiling) -Tightly attached and/or adhered ceilings -Suspended ceilings -Suspended gypsum board and plaster ceilings -Suspended acoustical ceilings -Lay-in panels supported by an exposed or concealed grid systems -Highly absorptive (v. gypsum board or plaster that is highly reflective) -Less expensive than gypsum board or plaster ceiling systems -Suspended linear metal ceilings -Suspended fire-resistance rated ceilings -Interstitial ceilings -Functions as in-between service space for complex mechanical and electrical systems in specialized medical, research, or lab facilities ▫

Rainscreen Principle in Metal and Glass Cladding

-External gaskets in curtain wall systems need only serve as deterrent seals, essentially a rainscreen, to discourage water from entering without necessarily barring its entry altogether. -Internal gasket serves as an air barrier, and the hollow spaces between the edges of the glass and the mullions act as pressure equalization chambers. -If water penetrates through the outer seals, it is conducted within spaces between the inner and outer seals down to weep holes in the outer face of the system. ▫

Monolithic Stone Cladding

-Fastened directly to the frame of the building. -Weight of each panel is transferred to two steel support plates by means of edge pockets that are cut into both sides of each panel at the stone mill. -Each panel is stabilized by a pair of steel angle struts that are bolted to the stone with expansion anchors in drilled holes. -Joints are closed with backer rod and sealant. -Nonstructural backup wall is required.▫

Types of Interior Walls - Applications of Rated Assemblies

-Fire Wall -Forms a required separation to restrict the spread of fire. -Extends continuously from the foundation to or through the roof. -Openings in rated fire walls are restricted in size and area. -Shaft Wall -Used to enclose a multistory opening through a building, such as a space for an elevator or spaces used for ductwork, conduits, or pipes. -Fire Barriers and Fire Partitions -Used to define smaller fire areas. Fire barrier must extend vertically from the top of one floor slab to underside of the next floor. -Other Nonbearing Partitions ▫

Handling and Placing Concrete

-Freshly mixed concrete is not a liquid but a slurry, a semistable mixture of solids suspended in liquid. -If vibrated excessively, moved horizontally for long distances in the forms, or dropped through constrained spaces, it is likely to segregate. Coarse aggregate may work its way to the bottom and water and cement paste may rise to the top. -Will result in concrete of nonuniform and generally unsatisfactory properties. -Segregation is prevented by depositing the concrete, fresh from the mixer, as close to its final position as possible. -If it must be moved large horizontal distances, it should be pumped through hoses or conveyed in buckets or buggies, rather than being pushed across or through the formwork. -If concrete must be dropped more than 3 to 5 feet, care must be taken to allow it to fall freely, or use dropchutes to break the fall of the concrete. ▫ -Concrete must be consolidated in the forms to eliminate trapped air and to fill completely the space around the reinforcing bars and all corners of formwork. -This can be done by repeatedly thrusting a rod, spade, or immersion-type vibrator into the concrete. Excessive agitation must be avoided, however, or segregation will occur. -Self-consolidating concrete (SCC) fills forms completely without requiring vibration or any other method of consolidation. -Formulated with more fine aggregates than coarse ones, which is a reversal of the usual proportions. -Includes special superplasticizing admixtures based on polycarboxylate ethers and other viscosity-modifying agents. -Result is a concrete that flows freely. -Consistent surface characteristics and crisp edges make it well-suited for production of high-finish-quality architectural concrete. ▫

Two-Way Flat Slab and Flat Plate Systems

-Generally more economical than one-way systems in buildings where the columns can be spaced in bays that are square or nearly square in proportion. -The two-way flat slab is a system suited to heavily loaded buildings. -Formwork is completely flat except for a thickening of the concrete to resist the high shear forces around the top of each column. -Traditionally accomplished with funnel-shaped mushroom capital and a square drop panel. -Today, the capital is usually eliminated to reduce formwork costs, leaving a drop panel to do the work alone. -Typical depths for the slab itself range from 6 to 12 inches. ▫

Plaster

-Generic term that refers to any of a number of cementlike substances applied to a surface in paste form that harden into a solid material. -Plaster is most often either gypsum plaster or portland cement-lime plaster (stucco). -May be applied directly to a masonry surface or to any of a group of plaster bases known collectively as lath. -Lath was historically thin wood strips, but today is typically either expanded metal or preformed gypsum boards. -Plaster is either applied by hand with a trowel, or spray-applied by machine.▫

Sloped Glazing

-Glass roofs present particular problems with respect to potential water leakage, because it is impossible to neutralize the force of gravity on a surface that is not vertical. -Moisture that condenses on the interior surfaces of the glass is likely to accumulate and drip onto the occupants of the space beneath. -Every sloped glazing system is designed by its manufacturer to include an internal drainage system. -This system collects any water that results from leakage or condensation and drains it to the outdoors. -Glass surfaces are sloped rather than flat -Slope enables gravity to assist in keeping water from ponding on the roof. -It causes condensate to run to the lower edge of each light of glass before dripping off. -Moves water through the drainage channels to the weep holes. ▫

Alternative Rating Systems for Assessing Green Buildings

-Green Home Building Guidelines, National Green Building Standard, Cradle-to-Cradle Certification, Net-Zero Building Certification, and others. -Passivhaus - Independent International Organization focused on performance-based assessment and certification of buildings with regards to energy efficiency. Originating in Darmstadt, Germany, there are now multiple affiliated organizations worldwide, including Passive House Institute US. -Emphasis on quantitative, as opposed to qualitative assessment criteria. -Emphasis on operational energy performance, as opposed to embodied energy or materials. -Certification based upon post-occupancy measurement data. -Original standards based upon cold climates, however standards have since been developed for hot and humid climates.

Prestressing

-If the initial tension, or prestress, in steel bars is of sufficient magnitude, surrounding concrete is never subjected to tension and no cracking will occur. -Beam is capable of carrying a much greater load with the same amount of concrete and steel than if merely reinforced in a conventional manner. -Prestressed concrete -Contains less concrete than reinforced members of equivalent strength. -Lighter weight, which makes them easier and cheaper to transport. -Structural precast concrete used for slabs, beams, and girders is typically prestressed. -Practical only with extremely high-strength steel strands that are manufactured for the purpose. These are made of cold-drawn steel wires formed into small-diameter cables. -Prestressing is accomplished in two different ways: pretensioning and posttensioning. ▫

Longer Spans in Steel

-Improved Beams -Castellated Beams - produced by flame cutting the web of a wide-flange section along a zig-zag path then reassembling the beam by welding its two halves point to point, thus increasing its depth without increasing its weight. -Plate girders -Rigid Steel Frames -Trusses -Space Truss or Space Frame -Arches -Tensile Structures -Fabric or Air-Supported Structures ▫

Reinforcing a Simple Concrete Beam

-In a simply supported beam under uniform loading, compressive forces follow a set of archlike curves that create a maximum compressive stress in the top of the beam at midspan, with progressively lower compressive stresses toward either end. -Mirrored set of curves correspond to paths of tensile (stretching) force, with stresses again reaching a maximum at the middle of the span. -In ideal scenario, bars would be bent to follow these forces to resist the higher stresses at the midspan of the beam. -Simpler rectilinear arrangement is usually substituted, consisting of a set of bottom bars and stirrups. -Bottom bars are placed horizontally near the bottom of the beam, leaving a specified amount of concrete below and to the sides of the rods as cover. -Concrete cover provides full embedment for the bars and protects them against fire and corrosion. ▫

Floor + Roof Decking

-In early steel frame buildings, shallow arches of brick or tile were often built between the beams, tied with steel tension rods, and filled over with concrete to produce level surfaces. -Metal decking - a simple sheet of steel corrugated to increase its stiffness. -Single corrugated sheets are commonly used for roof decking, where concentrated loads are not expected to be great and deflection criteria are not as stringent as in floors. -Also used as permanent formwork for concrete floor decks, with a reinforced concrete slab supported by the steel decking until the slab can support itself.▫ -Composite Metal Decking -Is designed to work together with concrete topping to make a stiff, lightweight, economical deck. -Metal decking serves as tensile reinforcing of the concrete, to which it bonds by means of special rib patterns in the sheet metal or by small steel rods or wire fabric welded to the tops of the corrugations. -Shear studs are welded every few inches to the top of each beam - shear studs create a strong shear connection between concrete slab and the steel beam. -Concrete Decks - cast-in-place or precast. -Roof Decking - designed to span long distances but light loading. ▫

Conceptual Approaches to Watertightness in the Exterior Wall

-In order for water to penetrate a wall, three conditions must be satisfied simultaneously: -There must be water present at the outer face of the wall. - There must be an opening through which the water can move. -There must be a force to move the water through the opening. -If any one of these conditions is not satisfied, the wall will not leak. -Four basic responses to preventing a leak: -Keep water away from the wall, if possible via overhangs or projections. -Try to seal every opening. This "barrier wall" typically proves unreliable. -Eliminate or neutralize the forces that move water through a wall. -Provide strategies for internal drainage or secondary defense, via cavities within the wall assembly that allow for drainage. ▫

Concrete Cover

-Insufficient concrete cover will lead to corrosion of steel reinforcing, which will also cause the concrete to flake and spall as the steel corrodes. -Concrete cover is what protects the reinforcement from fire. Thicker cover will maintain the integrity of the concrete longer in a fire.

Brick Masonry

-Is made of clay (fine-grained non-organic soil). • Is dug from pits, crushed, ground, and screened to reduce it to a fine consistency. It is then tempered with water to produce a plastic clay ready for forming into bricks. • Among masonry materials, brick is unique in its fire resistance and size. • Of all masonry unit types, bricks are the most resistant to building fires. • Traditional bricks are shaped and dimensioned to fit the human hand. • Because of their weight and bulk, they are expensive to ship over long distances. • Bricks are produced by a large number of relatively small, dispersed factories from local clays and shales.▫

Fabricator

-Job is to deliver to the construction site steel components that are ready to be assembled without further processing. -Begins with preparation of shop drawings that show exactly how each piece will be made and what its precise dimension will be. -Designs connections to transmit the loads indicated by the engineer's drawings. -Within limits of accepted engineering practice and the architect's design specifications, fabricator is free to design the connections to be made as economically as possible. -Shop drawings are submitted to the engineer and architect for review and approval prior to construction. -Fabricator places an order with a producer of steel for the stock shapes. ▫

Precast Concrete Beams, Girders, and Columns

-Made in several standard shapes -Projecting ledgers on L-shaped beams and inverted tees provide direct support for precast slab elements. -Ledgers conserve headroom by supporting slabs near the bottoms instead of slabs resting on top of beams. -Precast concrete columns are usually square or rectangular in section and may be prestressed or simply reinforced. ▫

Powder Coatings

-Manufactured with thermosetting powders that are composed of plastic resins, such as polyester, and pigments. -Powder is electrically charged and then sprayed onto the aluminum which is grounded so that the powder adheres to it electrostatically. -Component is then passed through an oven, where powder fuses to produce a hard, resistant coating, usually in a single application. -Advantages: durability, wide range of colors and finishes, and lack of organic solvents that cause air pollution. -Disadvantages: coating less integral and only opaque coatings possible.

Advantages and Disadvantages of Light Gauge Steel Framing

-Many advantages similar to those of wood light frame construction: -Versatile and flexible -Requires only simple, inexpensive tools -Furnishes internal cavities for utilities and thermal insulation -Accepts an extremely wide range of exterior and interior finish materials

Sealant Joints in the Exterior Wall

-Most exterior wall systems require sealant joints, seams that are closed with rubberlike compounds. -Role of sealant is to fill the joints between wall components, preventing the flow of air and/or water while still allowing reasonable dimensional tolerances for assembly and reasonable amounts of subsequent movement between the components. -Sealant joint widths are usually 3/8 to ¾ inch, but can be as small as ¼ inch and sometimes range up to 1 inch or more. ▫

Manufacture of Precast Concrete Structural Elements

-Most precast concrete elements are produced in permanent forms called casting beds. These average 400 feet long but can be 800 feet or more. -Cycle of precasting begins each morning, once elements cast the previous day have been lifted from the beds. -High-strength steel reinforcing strands are positioned and pretensioned. -Transverse bulkheads are placed at required intervals to divide the individual elements from one another. -For solid slabs, cored slabs, and wall panels, bulkheads are omitted and cured slab is simply sawed into required lengths. -Weld plates and other embedments are installed. -Concrete is placed in the bed, vibrated to eliminate voids, and struck off level. -Live steam or radiant heat is applied to accelerate curing. -Ten to twelve hours after pouring, concrete reaches 2500 to 4000 psi and has bonded to steel strands. Removed from beds and cycle restarts.

Details of Steel Framing

-Most steel frame connections use angles, plates, or tees as transitional elements between the members being connected. -Shear connection - joins only the web of the beam, but not the flanges, to the column. -Moment connection - it is necessary to connect the beam flanges strongly across the joint, most commonly by means of full-penetration groove welds. -Stiffener plates may be required if flanges are insufficiently strong. -Bolted moment connections are also possible though less common. -Many ways to create each joint type. ▫

Steps in the Manufacture of Portland Cement

-Portland cement may be manufactured from any of a number of raw materials, provided that they are combined to yield necessary amounts of lime, iron, silica, and alumina. -Lime is commonly furnished by limestone, marble, marl, or seashells. -Iron, silica, and alumina may be provided by clay or shale. -Exact ingredients depend on what is readily available, and recipe varies widely from one geographic region to another. -To make portland cement, the selected constituents are crushed, ground, proportioned, and blended. -Then they are conducted through a long, rotating kiln at 2600 to 3000 °F to produce clinker. -In U.S., standard bag of cement contains 1 ft3 of volume and weighs 94 lbs. ▫

Portland Cement Plasters

-Portland cement-lime plaster is also known as stucco (Lecture 25). -Similar to masonry mortar. Used where plaster is likely to be subjected to moisture, as on exterior wall surfaces, commercial kitchens, shower rooms, etc. -Not as "buttery and smooth" as gypsum plasters, making is somewhat more difficult to apply and finish to similar standards. -Shrinks slightly during curing▫

Precast Concrete Curtain Walls

-Precast concrete cladding panels - can be conventionally reinforced or prestressed. -Require close attention to surface finish, mold design, thermal insulation, attachment to building frame, and sufficient strength and rigidity in the building frame to support the weight of the panels. Factory production allows for high-quality molds and variety of surface finishes. -In precast concrete sandwich panels, thermal insulation is incorporated as an inner layer of the panel. Alternatively, insulation may be affixed to the back of the panel or may be provided in a nonstructural backup wall. -Reinforcing of panels must be designed to resist wind, gravity, and seismic forces, and to control cracking of the concrete. -Attachments must allow for relative movements of frame and cladding. -New material developments (carbon fiber reinforcing and ultra-high-performance concrete allow for thinner and lighter panels. ▫

White Portland Cement

-Produced by controlling the quantities of certain minerals, such as oxides of iron and manganese, found in the ingredients of cement, that contribute to cement's usual grey color. -Used for architectural applications to produce concrete that is lighter and more uniform in color. -Can be combined with other coloring agents to enhance the appearance of integrally colored concrete. ▫

Cast Steel

-Produced by pouring molten steel directly into molds and allowing the steel to cool. -More expensive, pound for pound, than rolled steel shapes. -Typically produced in small quantities. -Can economically utilize specialized steel alloys selected on basis of a part's unique requirements. -Can be non-uniform in section, can readily incorporate curves or complex geometries, and shapes can be carefully tailored to the particular requirements of the part. -Particularly well-suited for the production of custom-shaped connections for steel structures that are stronger, lighter, and more attractive than those possible with conventional rolled steel. ▫

Longer Spans in Sitecast Concrete

-Romans built unreinforced concrete vaults and domes, including the Pantheon in Rome (150 ft diameter). -Long-span beams and trusses are possible in concrete, including post-tensioned beams and girders and reinforced deep girders analogous to steel plate girders and rigid frames. -Barrel shells and folded plates derive their stiffness and strength from the folding or scalloping of a thin concrete plate to increase its rigidity and structural depth without adding material. ▫

Cold-Worked Steel

-Steel can be cold-worked or cold-formed (rolled or bent) in a "cold" state (at room temperature). -Light-gauge (thin) steel sheet is formed into C-shaped sections to make short-span framing members (Ref: Lecture 14). -Steel sheet stock is rolled into corrugated configurations for floor and roof decking in steel-framed structures. -Heavier sheet or plate stock can be cold-formed into square, rectangular, round, and elliptical hollow shapes then welded along the longitudinal seam to form hollow structural sections (HSS) -Also called "structural tubing"- are used for columns and for members of welded steel trusses and space trusses. -Hollow shape makes them especially suitable for members subjected to torsional (twisting) stresses or buckling associated with compressive loads. ▫

Production of Structural Shapes

-Steel is manufactured into a variety of standard shapes and sizes, the most ubiquitous of which is the I-beam shape for it's structural optimization. -Wide flanges are manufactured in two basic proportions: Tall and narrow for beams Squarish for columns and foundation piles -Accepted nomenclature for wide-flange shapes begins with the letter W, followed by the nominal depth of the shape in inches, multiplication sign, and the weight of the shape in pounds per linear foot. -Example: W12 x 26 -Refer to Manual of Steel Construction for more detailed information about each shape, including physical and structural properties. ▫ -Steel angles are versatile and used in many ways: - Short beams supporting loads -Lintels spanning door and window openings (esp. with masonry) - Connectors joining wide-flange beams, girders, and columns -Diagonal braces in steel frames -Members in steel trusses -Channel sections, tees, bars, plates, and sheets are also available and used in construction. ▫

Steel Bars for Concrete Reinforcement

-Steel reinforcing bars ("rebar") are hot-rolled like structural steel shapes. -Round in cross section and deformed with surface ribs for better bonding to concrete. -Bars are cut to standard length of 60-ft in the U.S. -In the U.S., bars are specified by a simple numbering system in which the number corresponds to the number of eighths of an inch of bar diameter. -Example: #6 rebar is 6/8 or 3/4-inch in diameter. -In other countries, "hard metric" system is used to balance diameter with the cross-section area. -Example: 19.5mm dia./ = 20M rebar / 300mm2 cross sectional area. -Typically manufactured according to ASTM A615, designated as "S" type steel. -Available in grades 40, 60, and 75, corresponding to steel with yield strengths of 40,000, 60,000, and 75,000 psi respectively. These grades also correspond to grades 280, 420, and 520 MPa (mega Pascals) in SI system. -Grade 60 (420) is generally most economical and readily available of these. -In structures with especially heavy reinforcing requirements, reinforcing bars with strengths as high as 120,000 psi may be used. -With high-strength bars, bar size may be reduced and the spacing between the bars can be increased, which reduces rebar congestion and makes it easier to place and consolidate concrete around the reinforcing. ▫

Structural Properties of Wood

-Strength depends chiefly on species, grade, and direction in which load acts with respect to grain. • Wood is several times stronger parallel to grain than perpendicular to grain. • Wood is stronger in compression than in tension.

Light Gauge Steel Construction

-The Structural Steel Framing members discussed last time are informally referred to as "hot-rolled" shapes because of the way in which they are made. -By contrast, light gauge steel framing is referred to as "Cold-Formed Metal Framing" or "CFMF" because these members are shaped out of sheet material that is not hot when shaped. -The noncombustible equivalent of wood light frame construction. -External dimensions of standard sizes correspond closely to the dimensions of the standard sizes of nominal 2-inch framing lumber. -Used in framing as studs, joists, and rafters in much the same way as wood light frame members are used. -Steel material is metallic-coated with zinc or aluminum-zinc alloy to provide long-term protection against corrosion. ▫

Precast Concrete Slabs

-The most fully standardized precast concrete elements are those used for making floor and roof slabs. -Four kinds commonly produced: -Solid slabs - short spans and minimum slab depths -Hollow-core slabs - intermediate spans, with internal longitudinal voids -Double tees - longest spans, eliminate nonworking concrete -Single tees - eliminate more nonworking concrete; need temp. bracing

Rainscreen Cladding and Pressure-Equalized Wall Design

-The term rainscreen principal originated with the concept of pressure-equalized wall design, and at one time it was used exclusively in reference to pressure-equalized cladding systems. -More recently, the term rainscreen cladding has come to be applied more broadly to any cladding system with a system of internal drainage, regardless of the extent of compartmentalization of the drainage space and the degree of pressure equalization that can be achieved. -Varying degrees of pressure equalization are achievable and the line between simple rainscreens and pressure-equalized walls is often indistinct. ▫

Two-Way Waffle Slab System

-The waffle slab or two-way concrete joist system is the two-way equivalent of the one-way concrete joist system. -Metal or plastic pans called domes are used as formwork to eliminate nonworking concrete in the slab, allowing considerably longer spans than are feasible in the two-way flat plate system. -Standard domes form joists 6 inches wide on 36-inch centers, or 5 inches wide on 24-inch centers in a variety of depths up to 20 inches. -Solid concrete heads are created around the tops of columns by leaving the domes out of the formwork in these areas. Head serves the same function as a drop panel in the two-way flat slab system. ▫

Unfinished Aluminum + Oxidation

-Though it is a very active metal chemically, aluminum does not corrode away in service because it protects itself with a thin, tenatious oxide film that seals the surface of the metal and discourages further oxidation. -Film protects aluminum but has a chalky, spotty appearance. -As a result, aluminum is usually treated in some way to provide better control of its appearance. ▫

Composite Masonry Walls

-To balance appearance and economy, solid masonry walls of multiple wythes can be constructed of multiple materials. - outer wythe of stone or face brick and a backup wythe of another material, often hollow concrete masonry. -Two wythes are bonded by horizontal steel reinforcement or steel tiles, and the space between can be filled with mortar. -Can be loadbearing or non-loadbearing. -Separate wythes are intimately bonded so that they behave as a single mass. -Evaluate differential thermal and moisture expansion characteristics of the two materials to be sure that the wythes expand or contract at similar rates. -In loadbearing applications, consider differential strengths and elasticities of the materials. ▫

Different Types of Portland Cement

-Type I (normal) - used for most purposes in construction. -Types II and V (resistance to sulphate attack) - used where the concrete will be in contact with water that has a high concentration of sulfates. -Type III (high early strength) - used in situations where a reduced curing period is desired (i.e. cold weather), in the precasting of concrete structural elements, or when the construction schedule must be accelerated. -Type IV (low heat of hydration) - used in massive structures such as dams, where the heat emitted during curing may raise the temperature to damaging levels. -Air entraining cements contain ingredients that cause microscopic air bubbles to form in the concrete during mixing. Air bubbles improve workability during placement of the concrete and greatly increase the resistance of the cured concrete to damage caused by freeze-thaw cycles. Used for pavings and exposed architectural concrete in cold climates

Formwork

-Uncured concrete is a shapeless slurry with no physical strength. -It must be shaped and supported by formwork until it has cured sufficiently to support itself. -Usually made of braced panels of wood, metal, or plastic. -Constructed as a negative of the shape intended for the concrete. -Must be strong enough to support the considerable weight and fluid pressure of wet concrete without excessive deflection. -During curing, the formwork helps to retain the necessary water of hydration in the concrete. -When curing is complete, formwork must pull away cleanly to not damage the concrete or forms, which are typically used repeatedly. -Limited acute corners that will trap or be trapped by the concrete. -Surfaces are usually coated with a form release compound, which is an oil wax or plastic, that prevents adhesion of the concrete to the form.

Other Common Uses of Light Gauge Steel Framing

-Used to construct many components of fire-resistant buildings: -Interior walls and partitions (Allen Chapter 23; Ref: Lecture 27) -Suspended ceilings (Allen Chapter 24; Ref: Lecture 28) -Fascias + Parapets -Backup walls for exterior claddings, including masonry veneer, exterior insulation and finish system (EIFS), glass-fiber-reinforced concrete (GFRC), metal panels, and various thin stone cladding systems (Allen Chapters 19 + 20; Ref: Lectures 22 + 23) -Where noncombustibility is not a requirement, metal and wood framing are sometimes mixed. Special care must be taken in the details to ensure that wood shrinkage will not create unforeseen stresses or damage to finish materials. ▫

Aluminum and Glass Framing Systems

-Used to construct windows, entrances, storefronts, and curtain walls. -Entrances -Systems of aluminum framed doors, hardware, aluminum framing, and glass typically used for commercial buildings. -Storefronts -Similar in appearance to curtain wall, but are based on simpler, lighter framing elements that are less expensive and quicker to assemble. -Most storefront systems span vertically no more than 10 to 12 feet. -Typically installed between floor slabs or within wall openings, and do not hang from the building like curtain wall systems. -More limited in their ability to resist wind loads and water penetration. -Typically not used more than three to four stories high on a building. -Used for floor-to-ceiling glass at ground level. ▫

Pretensioning

-Used with precast concrete members. -High-strength steel strands are stretched tightly between abutments in a precasting plant. -Concrete members are cast around the stretched steel. -The curing concrete adheres to the strands along their entire length. -After concrete has cured to a minimum compressive strength, strands are cut off at either end of the member. -This releases external tension on the steel, allowing it to recoil slightly, squeezing all of the concrete of the member into compression. -Member takes on a camber (lengthwise arching) at the time the steel strands are cut. -Camber disappears later when member is subjected to loads in a building. -Useful only for concrete members cast in precasting plants, as strong abutments required are expensive to construct except in a fixed location.

Veneer Plaster

-Veneer plaster base (gypsum veneer base) is a paper-faced gypsum board that comes in sheets 4-feet wide x 8- to 14-feet long, and ½" or 5/8" thick. -Veneer plaster is least expensive of the gypsum plaster systems and is competitive in price with gypsum board finishes in many regions. -Veneer base provides a very flat surface that can be finished with a layer of specially formulated dense gypsum plaster applied in one or occasionally two coats. -Plaster layer usually not more than 1/6 to 1/8 inch in total thickness. -Hardens and dries so rapidly that it can be painted the following day.

Installation of Mechanical, Electrical and Plumbing (MEP) + Data Services

-Vertical runs of pipes, ducts, wires, and elevators in a multi-story building are made through vertical shafts whose sizes and locations were determined at the time the building was designed - often by MEP consultant engineers. -Before the building is finished, each shaft is enclosed with fire-resistive walls to prevent the vertical spread of fire. -Horizontal runs of pipes, ducts, and wires are usually located just below each floor slab, to keep them up out of the way. May be left exposed or hidden above suspended ceiling. -Sometimes services are run horizontally between the structural floor deck and a raised access flooring system. -To house pipes where several plumbing fixtures are lined along a wall, a plumbing space (or chase) is created by constructing a double wall with space between. ▫

Gunnable Sealant Materials

-Viscous, sticky liquids that are injected into the joints of a building with a sealant gun. -They cure within the joint to become rubberlike materials that adhere to the surrounding surfaces and seal the joint against the passage of air and water. -Can be grouped in three categories according to the amount of change in joint size that each can withstand safely after curing. -Low-range sealants, also called caulks, are materials with very limited elongation (stretching and squeezing) capabilities, up to +/- 5% of the width of the joint. -Medium-range sealants have safe elongations of +/- 5% to 10% of the width of the joint. -High-range sealants can safely sustain elongations of up to +/- 50 to 100% of the width of the joint. This category includes polysulfides, polyurethanes, and silicones. They do not shrink during curing. ▫

Wide-Module Concrete Joist System with Joist Bands

-When fire-resistance requirements of the building code dictate a slab thickness of 4 ½ inches or more, the slab is capable of spanning a much greater distance than the normal space between joists in a one-way concrete joist system. -Led to development of the wide-module concrete joist system, or the skip-joist system. -Joists are placed 4 to 6 feet apart.▫

Firing of Bricks

After molding, bricks are dried for one to two days in a low-temperature dryer kiln. They are then ready for firing or burning. • Today, bricks are usually burned in either periodic or continuous tunnel kilns. • Periodic kiln is a fixed structure loaded with bricks, fired, cooled, and unloaded. • Long tunnel kilns are used for higher productivity. Bricks are passed continuously through long tunnels on special railcars to emerge at far end fully burned. • First stages of burning are water smoking and dehydration. Next stages are oxidation and vitrification, where temp rises to 1800 to 2400°F and clay is transformed into a ceramic material. May be followed by flashing for color. • Last step is controlled cooling. Entire process takes 40 to 150 hours.

Joining Steel Members

Bolts -May be either high-strength bolts (heat treated during manufacturing to develop greater strength) or lower-strength carbon steel bolts. -In contemporary construction, bolted connections rely almost exclusively on high-strength bolts. -Bearing-type connection: Bolts only need be installed to a snug-tight condition. Movement is resisted by member bearing on bolt directly. Bolts are stressed in shear. -Slip-critical (or friction type) connection - bolts are preloaded (tightened during installation) such that friction between adjoining faces (the faying surfaces) resists movement between the members. Bolts are stressed in tension. Used where small changes in alignment can be detrimental to performance: column splices, beam-to-column connections, etc. ▫

The Work of the Construction Professional: Constructing Buildings

Construction Project Delivery Methods: -Design/Bid/Build - Conventional Arrangement -Design/Build - Architect and Contractor are a single entity -Turnkey - Design/Build entity also provides financing for owner -Construction Manager - Typically engaged earlier in design process -CMa - Construction Manager Advisor -CMc - Construction Manager Constructor (CM at Risk) Paying for Construction Services: -Fixed Fee or Lump Sum - Typical with Design/Bid/Build -Cost plus a fee - Typical with CM Agreements -Guaranteed Maximum Price (GMP) - Variant on CM Agreement Construction Scheduling: Sequential v. Fast Track Construction ▫

Fire Basics +

Fire, also known as combustion, is a process of rapid oxidation at high temperatures. This releases hot gases, light, and invisible forms of radiation energy. • Oxidation is a common process. Rust is formed on iron through its interaction with oxygen in the air and we metabolize our food through oxidation in our bodies. The difference between fire and other oxidation processes is speed. Fire is the process of very rapid oxidation, which releases greater amounts of heat and other forms of energy in a chain reaction. • The electron transfer emits heat, which excites still more molecules in the fuel oxygen mix, continuing the oxidation reaction in a self-sustaining cycle.

Forces that Move Water Through a Wall

Gravity -Is a factor in pulling water through a wall only if the wall includes an inclined plane that slopes into—rather than out of—the building. -Usually simple to detail the exterior to avoid these types of inclined planes. -Sometimes a loose gasket or errant bead of sealant can create this condition even if components are designed correctly. ▫ Momentum -Momentum of falling raindrops can drive water through a wall only if there is a suitably oriented slot or hole that goes completely through the wall. -Neutralized by applying a cover to each joint in the wall or by designing each joint as a simple labyrinth. ▫ Surface Tension -Causes water to adhere to the underside of a cladding component. -Allows water to be drawn into the building. -Provision of a drip on any underside surface to which water might adhere will eliminate the problem. ▫ Capillary Action -This is the surface tension effect that pulls water through any opening that can be bridged by a water drop. -Primary force that draws transports water through the pores of a masonry wall. -Can be eliminated by making each of the openings larger than a drop of water can bridge. -Can also/alternatively provide a concealed capillary break somewhere inside the opening.▫ Air Currents and/or Pressure Differentials -Create an airtight plane, called the air barrier, behind the outer face of the wall. -Air barrier is protected from direct exposure to the outdoors by an unsealed, labyrinth-jointed layer known as the rainscreen. -Between the rainscreen and air barrier is a space known as the pressure equalization chamber (PEC).

Detailing Masonry Walls:

Interior flashings are installed by masons as they construct the wall. Where an internal flashing crosses the wall cavity, it should be turned up 6 to 9 inches at the back face of the cavity and penetrate the inner wythe by at least 2 inches. If the cavity is backed up by a concrete beam or wall, it may terminate in a reglet, a horizontal slot formed in the face of the concrete. ▫ At the outside face of the wall, the flashing should be carried at least ¾ inch beyond the face of the wall and turned down at a 45-degree angle. This creates a drip, allowing water draining from the flashing to drip free of the wall rather than being drawn under the flashing by capillary action and returning into the wall. Capillary action is the pulling of water through a small orifice or fibrous material by the adhesive force between the water and the material. A capillary break is a slot or groove intended to create an opening too large to be bridged by a drop of water and, thereby, to eliminate the passage of water by capillary action. The drip at the outside edge of flashing functions as a capillary break. Copper and stainless steel are the best flashing materials in masonry walls; galvanized steel, aluminum, and lead are unsuitable in masonry construction. ▫

Post-Tensioned Masonry Walls

Masonry walls may be post-tensioned by utilizing high-strength steel threaded rods or flexible tendons rather than conventionally reinforced with ordinary vertical reinforcing bars. Post-tensioned elements are anchored into the foundation and run vertically through the masonry wall, either in a cavity between wythes or in the cores of concrete masonry units. After wall is complete and mortar has cured, each rod or tendon is tensioned (stretched very tightly) and anchored in its tensioned condition to a horizontal steel plate at the top of the wall. Tensioning of the reinforcing places the entire wall under a vertical compressive prestress that is considerably higher than would be created by the weight of the masonry and the roofs/floors that it supports. Posttensioning strengthens the wall against wind and seismic loads.

Sizes

Maximum sizes and minimum thicknesses of sheets of cut stone vary depending on type of stone. Granite (igneous) - strongest stone - minimum 3/8 inch thick; maximum sheet size is 5 x 7 feet Marble (metamorphic) - minimum 3/4 inch thick Limestone (sedimentary) - weakest stone - minimum 2 inches thick (3 inches preferred); in a 6-inch thickness, limestone can be handled in sheets as large as 5 x 18 ft ▫

The Work of the Design Professional: Choosing Building Systems (continued)

Other Regulatory Issues -Americans with Disabilities Act (ADA) - Barrier--Free Design -Fair Housing Act (for multifamily housing) -U.S. Occupational Safety and Health ----Administration (OSHA) -State- specific limitations on Volatile Organic -Compounds (VOCs) -Conservation laws to protect wetlands and -environmentally-sensitive areas -Fire insurance companies - testing and certification of materials Standards-Setting Agencies -ASTM International: American Society for -Testing and Materials -ANSI: American National Standards Institute -NIST: National Institute of Science and Technology ▫

Design Requirements for the Exterior Wall

Principal Design Issues: -Convey design intent and meaning -Define the character of the project - further spatial and formal qualities -Negotiate and define social relationships Secondary Functions: -Resist Wind Forces -Control Water Vapor -Accommodate Movement -Thermal Expansion/Contraction -Moisture Expansion/Contraction -Structural Movements -Resist Fire - sometimes a primary function, depending on context -Address Installation Requirements for the Exterior Wall -Allow for Maintenance -Weather Gracefully ▫

Quantitative and Qualitative Information Required for Construction

Quantitative -Dimensional criteria, amount of material, locations, relationships between materials in assemblies or on surfaces -Typically recorded on annotated visual drawings Qualitative -Specifics of materials, minimum quality standards, performance requirements and/or behavioral properties of components -Typically recorded in bound 8 ½" x 11" text-based project manual -Manual includes specifications, general conditions, and procurement info MasterFormat -Established by the Construction Specifications Institute (CSI) -Outline for organizing information about construction materials and systems in drawings and project manual -Organized in 50 primary divisions ▫

Glass-Fiber-Reinforced Concrete (GFRC) Curtain Walls

Relatively new cladding material. Has several advantages over conventional precast concrete panels: Its admixture of short glass fibers furnishes enough tensile strength so that no steel reinforcing is required for short spans. Panel thicknesses and weights are about one-quarter of those for conventional precast concrete panels. Reduced weights saves money on shipping, makes the panels easier to handle, allows use of lighter attachment hardware, and allows loadbearing frame to be lighter and less expensive. GFRC can be molded into three-dimensional forms with intricate detail and an extensive range of colors and textures. Panels often attached to welded frame made of light gauge steel studs. Edges of GFRC facing are flanged so backer rods and sealant may be inserted between panels. ▫

HTimber Frame v. Post and Beam Construction

Timber Framing • Traditional form of wood construction with wood joinery • Timber pegs are usually critical structural links, and hence are made of robust wood species like oak, ash, or maple. Pegs are usually exposed and made prominent to emphasize their importance in the system. • Specialty craft that requires careful joinery, specialty tools, and skilled, patient carpenters. Timber Post and Beam • Utilizes mechanical fasteners and often steel plate connectors to join adjacent members together. • Connectors may be hidden or exposed in various ways. • May require additional structural elements like shear panels and infill framing to create a stable structure.

Reinforced Masonry Walls

Unreinforced masonry walls: Cannot carry such high compressive stresses as reinforced walls. Have little ability to resist tension forces. Unsuitable for use in regions with seismic risk or for walls subject to strong lateral forces (wind or earth pressures). Steel-reinforced masonry loadbearing walls: Combine complimentary materials to resist both compression (masonry) and tension (steel). Can be constructed thinner than comparable unreinforced walls. Savings in materials, labor, and floor area required for tall walls. In contemporary construction, all but the smallest and simplest masonry walls are reinforced. ▫

Floor and Roof Decks

• Building codes require that Type IV Heavy Timber buildings have floors and roofs of solid wood construction without concealed cavities. • Decking must be covered with finish materials of nominal 1-inch tongue-andgroove boards laid at right angles or diagonally to the structural decking. Plywood or composite wood panels are sometimes allowed.

Heartwood

• Consists of inactive cells that do not function in either water conduction or food storage. • The transition from sapwood to heartwood is accompanied by an increase in extractive content (biochemicals stored within the wood). • In some species, such as black locust, western red cedar, and redwood, heartwood extractives make the wood resistant to fungi or insect attack. • None of the sapwood of any species is resistant to decay. • As sapwood changes to heartwood, no cells are added or taken away, nor do any cells change shape. The basic strength of the wood is essentially not affected by the transition from sapwood cells to heartwood cells.

About Wood

• Consists primarily of long tubular cells whose long axes are parallel to the long axis of the trunk. • Cells are structured of cellulose, and are bound together by a softer cementing substance called lignin. • The direction of the long axes of the cells is referred to as the grain of the wood. • Grain direction is important to the designer of wooden buildings because the appearance and physical properties of wood parallel to grain and perpendicular to grain are very different. • Long fibers of wood allow for flexibility and the ability to resist shear loads.

Lumber Defects +

• Defects may be caused by growth characteristics of the tree from which it came or by manufacturing characteristics created at the mill. • Growth characteristics: • Knots - places where branches joined the trunk of the tree • Knotholes - holes left by loose knots dropping out of the wood • Decay + Insect Damage • Manufacturing characteristics: • Changes that take place during the seasoning process • Splits and checks - usually caused by shrinkage stresses • Crooking, Bowing, Twisting, and Cupping - caused by non-uniform shrinkage • Wane - irregular rounding of edges or faces if cut too close to edge of log

Growth Rings

• In temperate climates, cambium begins to manufacture new sapwood cells in the spring, when the air is cool and groundwater is plentiful, conditions that favor rapid growth. • Growth is slower during the heat of the summer, when water is scarce. • Springwood or earlywood cells are larger and less dense in substance than summerwood or latewood cells.

Heavy Timber Construction in Contemporary Practice

• International Building Code (IBC) establishes definition for "Type IV Heavy Timber (HT) Construction." This designates a particular construction type. • Includes both "timber frame" and "timber post and beam" construction. • Wooden structural members must meet certain minimum size requirements. Large timbers have greater capacity to absorb heat and are much slower to catch fire. • Exterior walls constructed of non-combustible materials, like concrete, masonry, or metal to reduce risk of fire spreading between buildings. • This type of construction historically referred to as mill construction, reflecting its origin in 19th-century brick masonry mill structures. • Traditionally, edges of timbers were chamfered (beveled at 45 degrees) to eliminate thin edges of wood that catch fire most easily. No longer a code requirement.

Sapwood

• Located between the cambium and heartwood. • Contains both living and dead cells and functions primarily in the storage of food. • In the outer layers near the cambium, sapwood handles the transport of water or sap. • The sapwood may vary in thickness and number of growth rings. Sapwood commonly ranges from 4 to 6 cm (1-1/2 to 2 in.) in radial thickness. • As a rule, the more vigorously growing trees have wider sapwood. Many second-growth trees of merchantable size consist mostly of sapwood. ▫

Lumber Dimensions

• Lumber sizes in the United States are given as nominal dimensions in inches, such as 2 x 4 ("two by four"). • Actual dimensions of the lumber are somewhat smaller due to sawing, seasoning, and surfacing of the members. • Nominal lumber dimensions are always written without inch marks. 1. Boards: pieces of lumber less than 2 inches in nominal thickness. 2. Dimension Lumber: pieces from 2 to 4 inches in nominal thickness. 3. Timbers: pieces nominally 5 inches and more in thickness. • Board Foot: volumetric unit of measure for lumber in the U.S. wood industry. • based on nominal dimensions, not actual dimensions. • A board foot of lumber is defined as a solid volume 12 square inches in nominal cross-section area and 1 foot long (eg.: 2x6 x 12" = 1 board ft.) • In other parts of the world, lumber is sold by cubic meter.

history masonry

• Medieval civilizations in Europe and the Islamic world brought masonry vaulting to a very high plane of development: palaces, markets, mosques, glazed tiles, fortresses, and cathedrals. In Central America, South America, and Asia, civilizations were evolving techniques in cut stone. • Industrial revolution in Europe and North America: • Mechanization of mining, transportation, and production techniques • Portland cement entered widespread use, allowing greater strength • Late 19th century, masonry displaced by iron or steel frames and reinforced concrete required for tall buildings in the city. • Invention of hollow concrete block in 19th century - much cheaper than cut stone and less labor than brick. • 20th century developments - steel-reinforced masonry, high-strength mortars, higher structural strength masonry units, and new types of masonry units. ▫

Mortar Hydration

• Modern masonry mortars are made with hydraulic cements. These are cements that cure by chemical reaction with water, a process called hydration. • In this process, a complex set of chemical reactions take up water and combine it with the constituents of the cement and lime to create a dense, strong crystalline structure that binds the sand particles and masonry units together. • Once hydraulic cements harden, they become water insoluble. • A mason can retemper mortar with water to keep it workable for short periods of time. • If unused mortar is more than 2 ½ hours old, it must be discarded because it has already begun to hydrate and cannot be retempered without reducing its final strength. In some projects, extended life admixtures may be used. ▫

Brick Classifications

• Most common bricks are facing brick, building brick, or hollow brick. • Facing bricks are used where appearance is important. • Building bricks used where appearance doesn't matter. • Facing and Building Bricks may be 100% solid but are more often cored, or frogged to reduce cracking during firing and reduce weight. • Hollow bricks are up to 60 percent void and are used primarily to enable the insertion and grouting of steel reinforcing.

Color of Bricks

• No two bricks are identical. • Color depends on the chemical composition of the clay or shale and the temperature and chemistry of the fire in the kiln. • Higher temperatures produce darker bricks. • Iron prevalent in most clays turns red in an oxidizing fire. • Other chemical elements interact in similar ways in the kiln to make other colors. • For bright colors, faces of bricks can be glazed like pottery either during the normal firing or during a subsequent firing process.

Schematic Design

• Site Plan • Floor Plans, including All Levels and Roof • Exterior Elevations • Building Sections • Study Models, Sketches, Digital Models • Narrative describing Building Systems and Materials (including structure and MEP approach) • Code Review

Construction Documentation

• Site Plan (Typically Provided by Civil Engineer) • Schedules (Doors, Windows, Partitions, Finishes, Materials, etc.) • Floor Plans, including Roof Plan • Exterior Elevations • Building Sections (Optional) • Wall Sections • Details (Interior + Exterior Conditions, Plan + Section Views) • Enlarged Plan Views of Vertical Circulation, Toilet Rooms, etc. • Interior Elevations • Reflected Ceiling Plans • Complete Structural and MEP (Mechanical/Electrical/Plumbing) Drawings • Specification describing materials, performance requirements, and level of finish (including structural and MEP components). • Furniture Plan + Specification (if applicable)

Three Major Methods for Molding Bricks:

• Soft mud process • Dry-press process • Stiff Mud Process

history of light wood construction

• The first uniquely American building system, developed in the first half of the 19th century. • Development accelerated by two technological breakthroughs of the period: • Boards and small framing members of wood became less expensive with advent of the water-powered sawmill. • Machine-made nails became remarkably cheap compared with the handforged nails that preceeded them.

Surface-to-Volume Ratio

• Tinder and Kindling: large surfaceto-volume ratio • Easily "kindles" or combusts • Fuel wood burns more evenly at a higher temperature

Manufactured Wood Components

• Trusses • Wood I-Joists • Panel Components • Framed Panels - sections of factory-assembled framing sheathed with plywood or OSB • Structural Insulated Panel (SIP) - two sheets of OSB or plywood joined firmly with stiff plastic foam core • Stressed-Skin Panel (SSP) - two sheets of OSB or plywood joined by dimensional lumber framing • Factory-Built Housing ▫

Excavation

• Walers - beams that span across the face of the sheeting • Heel blocks - temporary footings

Wood Shrinkage

• When edges of floors and roofs are supported on concrete or masonry, and interiors are supported on wood, there is a possibility for differential shrinkage. • Wood expands and contracts more with changes in moisture content, especially in the direction perpendicular to its grain. • Must detail buildings to minimize effects of differential shrinkage by eliminating cross-grain wood from the interior lines of support. • In traditional mill construction, pintles (steel caps) are used to carry the column loads past the cross-grain of the beams at each floor, so beams and girders can shrink without causing floors and roof to sag. • In contemporary practice, glue-laminated columns may run the full height of the building, with beams connected to columns with wood bearing blocks or welded metal connectors.▫

• Definitions of Phases and Deliverables for Design Development,

•Site Plan • Floor Plans, including Roof Plan + Code Plan • Exterior Elevations • Building Sections • Representative and/or Critical Wall Sections • Typical Details at Key Locations • Interior Elevations • Reflected Ceiling Plans • Structural and MEP Single Line Drawings • Outline Specification describing materials and level of finish (including structural and MEP components). Often includes cut sheets for major HVAC equipment and/or light fixtures.