Materials and Methods exam 2
define: Cold-worked or cold-formed steel
(rolled or bent) in a "cold" state (at room temperature).
cool roofs: thermal emittance solar reflectance
* Cool Roofs*: *Solar reflectance*, or albedo, is a measure of its tendency to reflect solar radiation rather than absorb it.*Thermal emittance* is a measure of a material's capacity to radiate infrared heat energy and cool itself as its temperature rises.
fly ash(pozzolan
*Fly ash*-• A fine powder that is a waste product from coal-fired power plants. • Increases concrete strength, decreases permeability. • Increases sulfate resistance. • Reduces temperature rise during curing. • Reduces mixing water • Improves pumpability and workability of concrete. • Reduces concrete drying shrinkage.
Plastic / Vinyl Window Frames
*Have very high coefficients of thermal expansion.* Most common material is *polyvinyl chloride *(PVC, vinyl), formulated with a high proportion of inert filler material to minimize thermal expansion and contraction. *Glass-fiber-reinforced plastic (GFRP) *windows, frequently referred to as fiberglass windows, are the newest product. More expensive than those made of wood or plastic.▫
Fire-Rated Glass two types
*Wired glass* Produced by rolling a mesh of small wires into a sheet of hot glass. When it breaks from thermal stress, wires hold sheets of glass in place so that the glass continues to act as a fire barrier. Carries a fire resistance rating of 45 minutes. *Optical-quality ceramic* (crystalline vs. amorphous solid) More stable against thermal breakage than any type of glass. Can achieve fire resistance ratings ranging from 20 minutes to 3 hours. ▫
two common types of tower cranes
*luffing-boom* crane is used in congested situations where as the *hammerhead boom crane* would be limited by obstructions
glazing putty has been replace with what?
*newer latex and silicone caulking* compounds can be applied more quickly and need not be painted.
Natural pozzolans
*• Natural pozzolans *-Used for reducing the internal temperature of curing concrete, reducing the reactivity of concrete with aggregates containing sulfates, or improving the workability of concrete. • *High reactivity metakaolin* is a unique white-colored natural pozzolan that enhances the brilliance of white or colored concrete. ▫
Framing in Light gauge steel construction
- *platform* fashion • Wall frames are sheathed in either wood panels or *gypsum sheathing panels* for noncombustible construction • Light gauge members are designed so they can be *nested* to form a tubular configuration that is especially strong and stiff.
Art glass -
- blown, molded, fused, and colored for decorative purposes. ▫
Stained glass and contemporary colored glass
- formulated with ingredients that alter the color of the glass.
Drapping in postensioning with presressed concrete beams
-Higher structural efficiencies are possible in a prestressed beam or slab if the steel strands are placed to follow as closely as possible the lines of tensile force • Draping is impractical in pretensioned members because the tendons would have to be pulled down at many points along their length. • Pretensioned strands can be harped, or pulled up and down in the formwork to make a downward-pointing or flattened V shape in each member that roughly approximates the shape of a draped tendon.
layering of green roofs
1.Plant material 2.Growth medium (engineered soil mix) 3.Filter fabric 4.Drainage layer and water retention 5.Rigid foam insulation boards - typically extruded polystyrene if placed above membrane, since it retains its insulating value when wet. May also be placed below membrane. 6.One or more protection layers 7.Waterproofing membrane - flood tested for watertightness prior to placing overlying components 8.Vapor barrier and air barrier - same requirements as for conventional roof 9.Roof deck and supporting structure - engineered to carry additional loads of green roof and maintenance vehicles/equipment
How much carbon and other impurities does ordinary cast iron have?
3-4%
single-strength glass to double-strength
3/32 inch thick glass- 1 inch thick. Thicker glass is generally required for larger windows and for windows in tall buildings, where wind velocities are high at higher altitudes.
How many different quality ypes of portalnad cement are there?
8 Type 1 (normal)- Type 8 (high resistance to sulfaic attack)
slump test
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.
thermal resistance
A material's effectiveness in resisting the conduction of heat is called .., abbreviated as R . The higher a material's R-value, the higher its resistance to heat flow and the better its performance as a thermal insulator
Nomenclature for wide-flange shapes
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
verrmicultie and perlite
Aggregates are usually expanded mica (*vermiculite*) or expanded volcanic glass (*perlite*). Both are much less dense than expanded shale. • Density is further reduced by admixtures that entrain large amounts of air during mixing.
what is air entraining?
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. ▫
Z-Brace
Also referred to as *plank* doors Primitive doors made of wood planks and z-bracing Used infrequently, because they are subject to distortions and large amounts of moisture expansion/contraction
Panel
Also referred to as *stile-and-rail* doors Avoid problems of moisture expansion/contraction in plank doors Panels are not glued to the stiles and rails,
Residential Entrance Doors
Are mounted on the interior side of the door frame. Swing inward
Thermal insulation can be installed in any of three positions:
Below the structural deck Between the deck and the membrane. Above the membrane. * for low slop it is typically between the deck and the membrane
Arches
Bend wide-flange shapes or join plates and angles
Joining Precast Concrete Elements
Bolting, welding, and grouting are all commonly employed.
History of glass two types
By 10th century A.D., Venetian island of Murano had become the major center of glassmaking, producing *crown glass* and *cylinder glass* for windows. -Initially a material for colored beads and small bottles, glass was first used in windows in Roman times.
labeling glass
By convention, glass surfaces are numbered starting from the exterior side of a glazing unit and working inward
Steel reinforcing for a simple beam in water downed text
COncrete resist compressive forces, horizontal steel bars resist compressive forces and verticle stirrups resist lesser, diagonal tensile forces
two types of roofs
Can be generally organized into two groups: low-slope roofs and steep roofs. ▫
Thermoplastic membranes
Can be softened by application of heat, and are joined at seams by heat or solvent welding. Most common types are *polyvinyl chloride (PVC)* and *thermoplastic polyelefin (TPO)*. Together account for 20% of market for low-slope roofs.
Thermosetting membranes
Cannot be softened by heat, and *must be joined by liquid adhesives or pressure-sensitive tapes.* Most commonly installed material is *ethylene propylene diene monomer (EPDM)*, a synthetic rubber that may include fiber or fabric reinforcing.
Projecting windows
Casement windows Awning windows Hopper windows Inswinging windows (top hinged or side-hinged) Pivot windows Tilt/turn windows - operate as inswinging side-hinged or as a hopper ▫
cast iron
Cast iron, produced from iron ore in a blast furnace
Electrochromic glass, also called switchable glass
Changes transparency in response to the passage of electric current.
define coarse and fine aggregate
Coarse aggregate is normally gravel or crushed stone, and fine aggregate is sand.
Casting a Concrete Column (and its footing)
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.
define Concrete
Concrete is a rocklike material produced by mixing coarse and fine aggregates, portland cement, and water and allowing the mixture to harden.
Architectural Concrete
Concrete that is intended as finished interior or exterior surfaces, and is specified with highly prescribed finish characteristics, is known as .. • After curing, texture of concrete can be changed through sandblasting, rubbing with abrasive stones, grinding smooth, and hammering.
three types of joints that control cracking of concrete slabs
Control joints, or contraction joints,-are intentionally weakened sections where the tensile forces can be relieved without disfiguring the slab. • Isolation joints, sometimes called expansion joints-• Relieve potential stresses by allowing freedom of movement of the slab with respect to other building parts or other portions of the slab.
Fritted Glass
Created by imprinting the surface of glass with silk-screened patterns of ceramic-based paints. The paints consist primarily of pigmented glass particles called *frit*. Often used to control the penetration of solar light and heat into a space.
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. • 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 or 1 ½-inches is common for slab and structural work. • Aggregate diameters up to 6-inches are used in dams and other massive structures. ▫
steep roofs
Drain themselves quickly, giving wind and gravity little opportunity to push or pull water through the roofing material.
Process of cement making: drying sinkage, curing, heat of hydration
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. ▫
Advantages of precasting vs. sitecasting
Erection process: Includes slabs, beams, girders, columns, and wall panels. Similar to that of structural steel. Faster, no wait as for sitecast. It can take place during adverse weather conditions: high or low temperatures that would prevent sitecast from happening. Disadvantages: Elements are heavy and bulky to transport: restriction on size and proportions of elements to 12-14 feet wide. Three-dimensional sculptural possibilities of sitecast are absent.
Erector (steel)
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 shopwelded and assembled components. Erector's workers, by tradition, are called *ironworkers*
Define: hot saw and cooling bed
Finished shape exits last set of rollers as a continuous length that is cut into shorter segments by a ... and segments are cooled on a ...
other fire resisters
Fire retardant filled double glazing Consists of a clear, heat absorbing polymer gel contained between two sheets of tempered glass. When heated, gel reacts to form opaque insulating layer. Intumescent interlayer laminated glazing Made of thin layers of transparent intumescent material sandwiched between multiple layers of annealed glass. When heated, intumescent interlayer reacts to form an opaque, insulating layer. Fire resistance ratings of up to 2 hours can be achieved. ▫
doors of egress
For ease of operation, most egress doors must be side-hinged Must not be too large or require much force to swing open
cee sections (Light gauge steel)
For studs, joists, and rafters, the steel is formed into C-shaped.
track sections or channel (light gauge steel)
For top and bottom wall plates & joist headers
Large glass doors (3)
French doors - hinged, open fully Sliding doors Terrace door - like French doors, but with only one operable leaf
Spandrel Glass
Frits are used to create special opaque glasses for covering *spandrel* areas (the bands of wall around the edges of floors) in glass curtain wall construction.
wet glazing components and dry glazing components.
Glazing materials most commonly used between the mullions and glass include.. Two types are often used in combination to utilize best properties of each.
Tempered Glass
Has higher residual stresses than heat-strengthened glass.Is four times as strong in bending as annealed glass. Used for as safety glazing - for all-glass doors that have no frame at all, hockey rink enclosures, basketball backboards, etc. More costly than standard annealed glass. All cutting to size, drilling, and edging must be done before heat treatment.
Float Glass
Has since been licensed to other glassmakers and has become the worldwide standard, replacing both drawn glass and plate glass. Resulting sheets of glass have parallel surfaces, high optical quality (virtually indistinguishable from that of plate glass), and brilliant surface finish.
Single-hung and double-hung windows
Have one or two moving *sashes* (frames in which the glass is mounted).
crown glass
Heated glass sphere was adhered to an iron rod called a punty opposite the blowpipe. Sphere was reheated and glassworker spun punty rapidly, causing centrifugal force to open the sphere into a large disk, or crown, 30 inches or more in diameter. When crown was cut into panes, one pane always contained "bullseye." ▫ Prior to introduction of modern glassmaking techniques, crown glass was favored over cylinder glass for its surface finish,
Define Hollow Structural Sections (steel)
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
Avoiding corosion
Ideal way to avoid corrosion between dissimilar metals is to use the same metal for every component of a sheet metal roofing system, including fasteners, anchor clips, roofing sheets, flashings, gutters, and downspouts. Another method of protection is to use insulating materials such as rubber or plastic between dissimilar metals.
dew point
If air continues to cool, it will reach a point where relative humidity is 100%. This is the temperature at which the air is fully saturated with water vapor, also known as th
Air vapor
In most of North America, this summer condition is not as severe as that in winter, and heating conditions predominate. Control of water vapor in building assemblies focuses primarily on the flow of vapor from interior to exterior. But the Water vapor is driven from the warm, damp outside air toward cooler, drier air inside. . The flow of water vapor from exterior to interior is the predominant problem to be solved
Blast furnace slag (also called slag cement)
Is a *hydraulic cement*, meaning that it reacts with water to form a cementitious compound. • May be added to concrete mixes to improve workability, reduce temperature rise during curing, and improve sulfate resistance • Byproduct of iron manufacture.
Fabricator
Job is to deliver to the construction site steel components that are ready to be assembled without further processing. Designs connections to transmit the loads indicated by the engineer's drawings. • Within limits of accepted engineering practice, 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.
Interior joist bearing (light gauge steel construction)
Joints are overlapped back to back and web stiffener is inserted at interior joist bearings.
Key points about water vapor and condensation
Key points to remember: Warmer air = more moisture = higher vapor pressure Cooler air = less moisture = lower vapor pressure Moisture will move from areas of high pressure towards areas of lower pressure. If properly designed and located (on warm/humid/high pressure side), vapor retarder may slow movement of moisture into the wall assembly, reducing likelihood of condensation occurring within the cavity
Materials of low and steep roof tops
Low-slope roof tops-Bituminous roof membranes Single-ply roof membranes Fluid-applied roof membranes steep roof tops- thatch, shingle, architectural sheet metal
Heat-Strengthened Glass
Lower-cost than tempered glass. Twice as strong in bending as annealed glass and is more resistant to thermal stress. Usually has fewer distortions than tempered glass.
Laminated Glass
Made by sandwiching a transparent *polyvinyl butyral (PVB)* interlayer between sheets of glass and bonding the three layers together under heat and pressure. Not as strong as annealed glass of the same thickness, but when laminated glass breaks, the soft interlayer holds the shards of glass in place rather than allowing them to fall out of the frame of the window. Useful for skylights and overhead glazing, because it reduces the risk of injury to people below in case of breakage. Qualifies as safety glazing, since it does not create dangerous, loose shards of glass when it breaks.
Glass
Major ingredient of glass is sand (silicon dioxide). When drawn into small fibers, glass is stronger than steel but not as stiff. In larger pieces, imperfections reduce useful strength, esp. in tension. ▫
vapor carrier of retarder
Material that is used to slow the diffusion of water vapor through a building assembly. Located toward the warmer side of the insulation in a building assembly. Restricts the diffusion of water vapor into the assembly from the side of higher vapor pressure, limiting chances for dew point conditions and condensation to occur within the assembly's cooler portions.
point-supported glass systems.
Metal fittings are used to join corners and edges in ..
Roof Deck
Minimum slope of* ¼ inch per foot* (1 in 50, or 2 percent) To create the slope, two principal methods: Beams are sloped by varying the heights of columns. Deck is constructed level and slope is created by a layer of thermal insulation of varying thickness installed on top of the deck. If slope is too shallow, *ponding* occurs. This involves the formation of puddles of water that stand for extended periods of time, leading to premature deterioration of the roofing materials in those areas, and/or collapse. ▫
casting beds
Most precast concrete elements are produced in permanent forms called
Electric arc furnace process
Most structural steel in North America is made from recycled scrap by this process and Recycled content of steel made by this process is 90 percent or higher
Storm Doors
Mounted on the outside of the frame of exterior doors Swing outward Improves wintertime thermal performance
Screen Doors
Often substituted for storm doors in summer Can be a *combination door*, with interchangeable panels
U-Factor
Performance as a thermal insulator is quantified as its U-Factor. U-Factors are mathematical reciprocals of R-values. Lower U-Factors = improved thermal performance. U-Factor is the reciprocal of R-value 1/U = R (e.g., 1/0.34 = 2.94)
processing of steel and its effect on the environment
Process releases 4550 lbs of gaseous emissions, and 600 lbs of slag and 50 lbs of dust are generated. ▫
Heat-Treated Glass
Produced by reheating *annealed* glass in an oven and then cooling *(quenching)* both of its surfaces rapidly with blasts of air while its core cools much more slowly. Resulting glass is stronger in bending than annealed glass and more resistant to thermal stress and impact. Useful for windows exposed to heavy wind pressures, impact, or intense heat or cold.
types of windows
Projecting windows Sliding windows Single-hung and double-hung windows Fixed windows
standard precast beam and girder shapes
Rectangular beam, ledgers, L-shaped beam, inverted Tee beam, AASHTO (American Association of State HIghway and Transportation Officials) girders designed for bridges but used in buildings sometimes.
Egress Windows
Required in every room used for sleeping purposes. Must satisfy four International Residential Code (IRC) criteria:
plate glass
Result was a costly glass of near-perfect optical quality in sheets of unprecedentedly large size. Neither crown glass nor cylinder glass was of sufficient optical quality for the fine mirrors desired by the 17th-century nobility.
Two common methods of arranging stabilizing elements:
Rigid core and rigid perimeter & diaphram action
history of concrete
Romans were the inventors of concrete construction. • 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. ▫
All about low slope roof tops: Roof deck Thermal insulation Air barrier through the roof assembly. Vapor barrier - Roof membrane Drainage components - Flashing -
Roof deck - structural surface that supports the roof. Thermal insulation - slows the passage of heat into and out of the building. Air barrier - restricts the leakage of air through the roof assembly. Vapor barrier - essential in colder climates or when enclosing spaces in humid environments to prevent vapor from condensing within it. Roof membrane - impervious sheet material that keeps water out of the building. Drainage components - remove the water that runs off the membrane. Includes roof drains, gutters, and downspouts. Flashing - At edges of membrane and wherever it is penetrated by pipes, vents, expansion joints, electrical conduits, or roof hatches, special flashings and details must be installed to prevent water penetration.
Green Roofs
Roofing systems covered with vegetation and additional materials needed to support plant growth.
steep roofs (3 general catogories)
Roofs with a pitch of 2:12 (17 percent) or greater are referred to as "steep roofs. Three general categories: Thatch Shingles Architectural Sheet Metal
Universal Metal Stud Designators
S = Stud or joist sections with flange stiffeners (Cee shapes) T = Track sections U = Cold rolled channel or channel studs (without flange stiffeners) F = Furring/Hat channels • The flange width and web depth are expressed in 1/100 inches. • Minimum base metal thickness is expressed in mils (1/1000 inches).
shear connection and moment connection (steel framing)
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.
Glazing
Single glazing is acceptable only in the mildest climates because of its low resistance to heat flow and the likelihood that moisture will condense on its interior surface in cool weather. More than 90% of all residential windows sold in North America have two or more layers of glass. ▫
Flush ( 3 types)
Solid Core - wood blocks or wood composite material Hollow Core - interior spacers of paperboard or wood Mineral Core - can be used as fire doors ▫
Cylinder glass
Sphere, heated to a molten state, was swung back and forth, pendulum fashion, on the end of the blowpipe to elongate it into a cylinder. Hemispherical ends were cut off and remaining cylinder was slit lengthwise. Then reheated, opened, and flattened into a rectangular sheet of glass later cut into panes of any desired size.
Architectural Sheet Metal Roofing types of seams: 3 types
Standing Seam, Flat Seam, Standing Seam (Batten)
steam cured
Steam furnishes heat to accelerate hardening and moisture for full hydration
Advantages of cold-worked steel:
Steel gains strength because cold-working aligns its crystalline structure.
Production of Steel Shape
Structural Mill - Hot steel passes through rollers that squeeze metal into progressively more accurate versions of the final product. Hot Saw - Continuous steel beams cut into desired lengths by hot saw Cooling Bed - Segments are allowed to cool Roller Straightener - Corrects residual crookedness
define: blended cement.
Supplementary cementitious materials may be added to portland cement during the cement manufacturing process, in which case the resulting product is called a
"hot-rolled" (steel)
The Structural Steel Framing members because of the way in which they are made.
Ties (for reinforcing concrete columns) and the 2 types
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)
solar heat gain coefficient (SHGC)
To evaluate effectiveness of glass in reducing heat gain, a measure called the...is used. SHGC is the ratio of solar heat admitted through a particular glass to the total heat energy striking the glass.
galvanic series.
To facilitate the prediction of the corrosion potential of metal pairs, metals may be listed in... Most anodic, or active, metals are at one end of the list and the most cathodic, noble or passive, metals are at the other end. Metal pairs positioned far apart in the series have greater corrosion potential than pairs closer to each other.
Bituminous Roof Membranes for low slope roofing
To protect membrane, a layer of crushed stone or other mineral granule aggregate is embedded in the top surface Assembled in place from multiple layers of asphalt-impregnated roofing felt bedded in additional layers of bitumen.
Wood Frame Windows
Traditional frame material for windows. Fairly good insulator,
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. • 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
Types (2) of glazed units for installation of windows on roofs
Unit skylights - typically fixed Roof window - typically operable, often rotating to allow for cleaning
Fluid-Applied Roof Membranes
Used primarily for domes, shells, and other complex shapes that are difficult to roof by conventional means.
Uses of light gauge steel construction
Used to construct many components of fire-resistant buildings • Where noncombustibility is not a requirement, metal and wood framing are sometimes mixed.
Light to solar gain (LSG) ratio
Useful measure of overall energy-conserving potential of glass Defined as the visible light transmittance divided by the solar heat gain coefficient.
ALl about low slope roof tops
Usually defined as one whose slope is less than 2:12, or 17 percent- "2:12" is the ratio of rise to run.
structural tee sizes (steel)
WT 13.5x 47 (or is made with American standard it is designated ST). Nominal depths of 2" to 9" in 1" increments and 10.5" to 18" in 1.5" increments
Low-slope roofs
Water drains relatively slowly from the surfaces. Major advantages of low-slope roofs: Can cover a building of any horizontal dimension, whereas a steep roof becomes uneconomically tall when used on a very broad building. Much simpler geometries make them easier and less expensive to construct. Can serve as balconies, decks, patios, landscaped gardens, or parks. ▫
vapor pressure
Water vapor is a gas and exerts pressure, on the surfaces that contain it.causes water vapor to diffuse outward, possibly leavign condensation
condensation.
When air is cooled below its dew point, it can no longer contain all its water vapor and some of the vapor turns to liquid.
Galvanic Corrosion
When different metals come into contact in presence of moisture, electric current flows between them. * anode*-The metal donating electrons, called the anode, experiences an accelerated rate of corrosion. * cathode,* The metal receiving electrons, called the cathode, experiences corrosion at a reduced rate.
cambered (steel)
Where called for, beams and girders are cambered (curved slightly in an upward direction) so that they will deflect into a straight line under load.
Steel Shapes in Use:
Wide Flange ("I" shape) - (e.g. W21x83, nominally 21" deep and 83lb/lineal foot) Used for most beams and columns American Standard ("I" shape) - (e.g. S18x70, nominally 18" deep and 70lb/lineal foot) Similar to wide flange in shape and use but less efficient Angle ("L" shape) - (e.g. L4x3x⅜, L=angle, 4x3=nominal depths of the two legs, ⅜=thickness of legs). Very versatile, can be used for very short beams or lintels in masonry construction. Also connect wide-flange beams, girders, and columns. Channel ("C" shape) - (e.g. C9x13.4, nominally 9" deep and 13.4lb/lineal foot) - Used for truss members and bracing, as well as short beams and lintels Structural Tee ("T" shape) - WT13.5x47, denotes a T split from a W27x94, where 13.5=nominal depth and 47=lb/foot.
Insulating glass
Window glass is a poor thermal insulator. Double- or triple-glazed units are called *insulating glass units (IGUS)*
Tensile Structures
Wires of cold-drawn steel to make tentlike roofs with long spans.
Types of Wood Doors
Z-Brace Panel Flush
define: Structural mill or Break down mill
a beam blank is reheated and passed through a series of rollers that squeeze the metal into progressively more refined approximations of the final shape.
key (concrete)
a groove that will form a mechanical connection to the wall, is sometimes formed in the top of the footing
Define: Alloy
a homogeneous mixture or solid solution of two or more metals, the atoms of one replacing or occupying interstitial positions between the atoms of the other: Brass is an alloy of zinc and copper
define: Metal decking
a simple sheet of steel corrugated to increase its stiffness. • Single corrugated sheets are commonly used for *roof decking* •Usually *puddle welded* to joists, beams, and girders by welding through the decking to the supporting members below with a welding electrode
Define: Rivet (steel)
a steel fastener consisting of a cylindrical body and a formed head. • As it cools, it shrinks, clamping the joined pieces together and forming a tight joint. • Has been completely replaced in contemporary construction by less labor-intensive techniques of bolting and welding ▫
Water-reducing admixtures
allow a reduction in the amount of mixing water while retaining same workability, which results in a higher-strength concrete.
Freeze protection admixtures
allow concrete to cure satisfactorily at temperatures as low as 20 °F
High-rangewater-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.
near-infrared (NIR) radiation,
an invisible component of solar radiation that accounts for over half of the total heat energy radiated by the sun. ▫
Eave-
anchor clips are sandwiched between the ceiling joists and rafters to hold the roof framing down to the wall.
Foundation clips (light gauge steel construction)
anchor the entire frame to the foundation
Define: Steel
any range of alloys that have contain less than 2% carbon
Modified bitumens and how sheet are bonded (4)
are asphalt materials to which compounds have been added in order to increase the material's flexibility, cohesion, toughness, and resistance to flow. Sheets are bonded together: Hot-mopped - relies on the application of hot asphalt to bond the sheets. Torch-applied - open-flame apparatus is used to thermally fuse the underside of the sheet to the top surface of the underlying sheet. Cold process or cold-applied adhesive - uses liquid adhesives. Self-adhered membrane - relies on factory-applied adhesives. Top or *cap sheet* is surfaced with mineral granules, thin metallic laminates, or asphaltic or elastomeric coatings for greater resistance to ultraviolet deterioration, wear, and fire. Bituminous roofing systems account for approximately 40% of the market for low-slope roofing membranes, with the larger portion of this share belonging to modified bitumen systems.
Coloring agents
are dyes and pigments used to alter and control the color of concrete. ▫
• Ganged forms
are large units made up of a number of panels supported by the same set of walers. Handled by crane and reduces need for framework for concrete construction
Wide flanges
are manufactured in two basic proportions: • Tall and narrow for beams • Squarish for columns and foundation piles
Define Pozzolans used for supplementary cemenitious material) and fly ash,silica fume,
are materials that react with the calcium hydroxide in wet concrete to form cementing compounds. Includes •
High-strength, low-alloy steels vs. mild structural steel
are stronger than mild structural steel
Wide-flange shapes (steel) and their nominal dimensions
are used for most beam and columns. The smallest depth nominally is 4 in. and the largest is 44 in. Weight ranges from 9 to 730lbs.
LIghtweight aggregates
are used instead of sand and crushed stone for various special types of concrete.
Corrosion inhibitors
are used to reduce rusting of reinforcing steel in structures that are exposed to road deicing salts or other corrosion-causing chemicals.
Rule of thumb: materials used on the opposite side of an assembly from a vapor retarder should have a vapor permeance..
at least 10 times that of the vapor retarder itself. ▫
Structural Panel Metal Roofing for Low-Slope Roofs
because folded shape of metal roofing gives it sufficient stiffness to support itself and normal loads between purlins without the need for a structural deck beneath. Traditional forms of roofing are not self-supporting, and are referred to as *architectural sheet metal roofing*. These are typically used on steep roofs, and are not self-supporting (they need a structural deck beneath them). ▫
Photochromic glass
becomes darker when exposed to bright light.
Thermochromic glass
becomes darker when warmed by the sun
Cycle of precasting
begins each morning after previous cured concrete was removed: First: steel reinforcing is positioned and pretensioned. Second: transverse bulkheads places at required intervals to divide elements. Omitted for solid slabs, cored slabs and wall panels. Third: weld plates and other embedments installed Fourth: Concrete poured, vibrated and struck off level. Fifth: Steam and heat applied to accelerate curing. Sixth: 10-12 hrs after pouring concrete reaches 2500-4000 psi, bonded to steel strands, removed from beds.
Crystal Glace Palace exposition
by Joseph Paxton built in london out of cast iron and glass. Burned to the ground.
Limitations of cast and wrought iron
cast is brittle and wrought is expensive
• Accelerating admixtures
cause concrete to cure more rapidly, and r*etarding admixtures* slow its curing to allow more time for working with the wet concrete.
Photovoltaic glass
coated with thin film of amorphous silicon that generates electricity from sunlight.
Define: Roller straightener
corrects any residual crookedness
Extended set-control admixtures
delay the curing reaction in concrete for any period up to several days. Stabilizer component is added at time of initial mixing to defer the onset of curing indefinitely. Activator component is added when desired to reinitiate the curing process
The strength and stiffness of a member (light guage steel)
depend on the shape and depth of the section, and the *gauge* (thickness) of steel sheeting used to make it. ▫
butt-joint glazing
ead and sill of the glass sheets are supported conventionally in metal frames, but vertical joints are eliminated. Vertical joints between sheets of glass are made by injection of a colorless silicone sealant
Sliding windows
essentially single-hung windows on their side.
Channel sizes (steel)
ex: C9x13.4 nominal depths of 3"4"5"6"7"8"9"10"12"15"
Angle Sizes ( steel)
ex: L4x3x3/8. The first two numbers are the nominal depths of the two legs and the last one is the thickness of the legs
American Standard sizes (steel)
ex: S18x70. nominal depths of 3" 4" 5" 6" 7" 8" 10"12" 15" 18" 20" 24"
Longer Spans in Sitecast Concrete (8)
ex: space frame, rigid frame, vierendeel truss, arch, folded plate, barrell shell, dome, hypberolic parabloid shell
wide-flange sizes (steel)
example: W 21x81. Nominal depths from 4- 18 inches in 2 inch increments and 18-36 inches in 3 inch increments
• Self-consolidating concrete (SCC)
fills forms completely without requiring vibration or any other method of consolidation bt Formulated with more fine aggregates than coarse ones, which is a reversal of the usual proportions.
Structural glass
fins or laminated glass beams function to resist wind loads in very tall or wide curtain walls.
flying formwork
floor slabs that are fabricated in large sections that are supported on deep metal trusses and moved from one floor to the next by crane.- reduces need for framework in concrete construction
Single Ply roof membranes and the two groups
for low slope roofing Require less on-site labor than bituminous roof membranes. Unlike multi-ply bituminous membranes, single-ply membranes have no *redundancy.* Fall into two groups: *thermoplastic* and *thermosetting*
Different materials for shingles : 5 types
for steep roofs *Wood Shingles and Shakes* recommended to be installed over a *breather mat*: A wiry plastic mat that creates a continuous airspace. Permits airflow under the shingles. Prevents accumulation of moisture and accelerated deterioration. Expected to last *15 to 25* years under average condition *Asphalt or Composition Shingles* Life expectancy of 15 to 25 years, Covers 90% of single-family houses in North America. Inexpensive to buy, quick to install, and moderately fire resistant. *Slate Shingles* Slate roofs typically last 60 to 80 years Suitable for buildings of the highest quality. First cost is high. * Clay Tiles* Many other patterns of clay tiles are available, both *glazed* and *unglazed*. * Concrete Tiles* Expected lifetimes range from *30 to 75 years*, depending on climate and the resistance of the tiles to water absorption
Shingles
for steep roofs Applied to the roof in small units and in overlapping layers with staggered vertical joints. Used to refer to both wood shingles and shakes, asphalt shingles, slates, clay tiles, and concrete tiles. ▫
Grade 60 (420) reinforcing steel
generally most economical and readily available of these.
Chromogenic glass
glass that can change its optical properties
annealed
glass that is meaning it is cooled slowly under controlled conditions to avoid locked-in thermal stresses.
Mirror glass
has a thin silver-based coating on its back face.
web stiffener (light gauge steel construction)
helps transmit vertical forces from each stud through the end of the joist to the stud in the floor
Depleted alloying materials for steel
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.
anchor clips (light guage steel construction)
holds the roof framing down to the wall
Panic hardware
horizontal bars or similar devices that unlock and unlatch the door whenever the bar is depressed
ballast
in Insulation Above the Membrane: The Protected Membrane Roof (PMR)..crushed stone or gravel, thin concrete layer laminated at the factory to the upper surface of the insulating board, or interlocking concrete blocks.
when were cast and wrought iron used for construction?
in the first half of the 19th century
clad wood windows
in wood frame windows when Are normally covered with wood veneer on the interior and clad (covered) with plastic or aluminum on the exterior.
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.
Lights or lites
individual pieces of glass.
Glazier
installer of glass.
Raw materials for steel are..
iron ore, coal, limestone, air and water
wrought iron
iron that has been purified by beating it repeatedly with a hammer, contains less carbon than most steel alloys
slab-on-grade
is a level surface of concrete that lies directly on the ground
Open-web steel joist (OWSJ) and its 3 series
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 • LH series joists - designated as "Longspan" • DLH series joists - "Deep Longspan"
Aerogel
is a silicon-based foam that is 99.8% air. Used to fill the cavity in double-glazed glass or plastic products. Has a good light to solar gain ratio, making it an efficient source of diffuse, low-contrast natural daylight.
two-way flat slab (Two-Way concrete Systems)
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. Typical depths for the slab itself range from 6 to 12 inches.
Lightweight insulating concrete (for low slope roofing)
is an economical insulating material that also creates a nailable roof deck.
Tinted glass
is made by adding small amounts of selected chemical elements to the molten glass mixture to produce desired hue and intensity of color in greys, bronzes, blues, greens, and golds.
Visible light transmittance (VT) is
is measured as the ratio of visible light that passes through the glass relative to the amount of light striking it. Clear glass has visible light transmittance of 0.80 to 0.90, meaning that 80 to 90 percent of the visible light striking the glass passes through it. Visible light transmittance ranges from 0.75 in light tints to 0.10 for dark grey.
sash
is the frame in which the glass in mounted.
welding in steel light frame construction
is very common to assemble panels
Capillary break (for slab-on-grade)
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.
Fixed windows
least expensive and least likely to leak air or water.
"Cold-Formed Metal Framing" or "CFMF" ASTM standard A1003-
light gauge steel framing because these members are shaped out of sheet material that is not hot when shaped. (The noncombustible equivalent of wood light frame construction.) ASTM standard A1003-metallic coated with zinc or aluminium-zinc alloy to provide long term protection against corrosion
define: mils
measurement of the Minimum base metal thickness in light steel frame constuction
Joining metal components in light gauge frame construction (two types)
mechanilcally( rivets, bolts, or screws) or fusion (welding) sheet metal is joined commonly with interlocking, folded connections
structural glazing,
metal mullions lie entirely behind the glass, with the glass adhered to the mullions with structural silicone sealant, or more recently, acrylic foam structural glazing tape.
Shear walls - (steel) (3)
method of stabilizing the frame - stiff walls made of steel, concrete, or reinforced concrete masonry. They function like braced frame. Moment connections are not required.
Braced frame (steel )
method of stabilizing the frame creates stable triangular configurations, or diagonal bracing, within the otherwise unstable rectilinear geometry of a steel building frame.
Eccentrically braced frame (steel)
method of stabilizing the 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.
Moment-resisting frames -
method of stabilizing the frame rely on moment connections between beams and columns
Antireflective glass
minimizes residual reflections that normally occur.
steamed cured
mostly seen in precasting
advantages and disadvantages of light gauge steel framing over masonry
much lighter** easier to insulate accept wiring and pipes more readily can proceed under wet or cold conditions • Specific disadvantages of light-gauges steel when compared with masonry: • Masonry walls much stiffer and more resistant to passage of sound than steel-framed walls. ▫
self-drilling, self-tapping screws (light frame steel construction)
nails that drill their own holes and form helical threads in the holes as they are driven.
advantages of Light gauge steel framing over Wood:
noncombustible lighter less material (greater spacing) longer span more uniform stable dimensionality no termite decay
Thermal bridging
occurs when a part or parts of a building envelope assembly with low thermal resistance penetrate the thermal barrier. should be avoided by detailing thermal breaks.
Sitecast Framing system
one way system v. two way system
ballasting and Traffic decks (low slope roofs)
oof membranes may be covered after installation with a ...of loose, rounded stone aggregate ranging in size from 1 ½ to 2 ½ inches in diameter or with precast concrete paver blocks.-Ballast holds the membrane down against wind uplift and protects the membrane from ultraviolet light and physical wear. Traffic decks are installed for walks, roof terraces, and sometimes driveways or parking surfaces. Two different details are used: Low blocks of plastic or concrete are set on top of the membrane to support corners of heavy square paving stones or slabs with open joints. Drainage layer of gravel or *no-fines concrete* (very porous concrete whose aggregate consists solely of coarse stone of a single size)
Ridge (light guage steel construction)
pair of nested joints makes a boxlike ridge beam.
Carbon Fiber Reinforcing
precast cement Beginning to substitute mild steel reinforcing. Doesn't need protection from corrosion, reducing amount of concrete used Lower thermal conductivity Improved structural efficiency, higher tensile strengt
define Joist girders
prefabricated steel trusses designed to carry heavy loads, esp. bays of steel joists; can range from 20 to 72 inches deep.
Pretensioning and postensioning (in accomplishing prestressing concrete)
pretensioning:1) stress the reinforced steel 2) put the concrete cast on and let it cure (bonded to the reinforced steel) 3) cut the steel reinforcements and the concrete goes into compression and takes on a *camber* ( lengthwise arching) -postentiosning: concrete is not allowed to be attached to the steel reinforcements, after concrete has cured the strands are tensioned with a hydraulic jack and anchored to the ends of the beam. Same result as Pretensiong
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
Reinforcing of concrete
put the reinforcing steel where there are tensile forces in a structural member, and let the concrete resist the compression. • Typically manufactured according to ASTM A615, designated as "S" type steel.
• Shrinkage-reducing admixtures
reduce drying shrinkage and the cracking that results.
Glazing
refers to the installing of glass in an opening or to the transparent material (usually glass) in a glazed opening.
Vacuum-insulated glazing units
rely on evacuation of most of the air from the space between the glass sheets, and are currently under development. To improve thermal performance
3 methods of fastening techniques for the joining of steel shapes to a construction frame
rivets, bolts, or welds
Weep holes
should be provided to drain water from the horizontal mullions to the exterior of the window frame. ▫
• One-way solid slab concrete
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.
Shotcrete
sprayed into place from the nozzle of a hose by a stream of compressed air.-- reduces need for framework in concrete construction
A572 Grade 50
steel that is most commonly used today
Architectural Sheet Metal Roofing and supplied in two ways
steep roofs *lead* *copper* *lead-coated copper* *zinc* *stainless steel and titanium* Most Materials listed above—lead, copper, lead-coated copper, zinc, stainless steel, titanium, form *self-protecting oxide coatings* (patinas) that provide long-lasting resistance to corrosion. *aluminum, or metallic-coated steel* need to having corrisson resisting stuff sparyed onto them Fabricated and supplied in two distinct ways: sheet metal roofing or preformed metal roof panels.
short crosspieces (light gauge steel construction)
take the last joist at the edge of the building and help transmit stud forces through to the wall below
glass mullion systems
tempered glass sheets are stabilized against wind pressure by perpendicular stiffeners, also made of tempered glass, or by systems of tension cables.
diaphragm action (steel frame construction)
the rigidity possessed by a thin plate of material such as a welded steel deck with a concrete topping- used in rigid core and rigid perimeter stabilizing methods
Muntins
thin wooden bars in which the glass was mounted within each sash.
sheet metal roofing
type of architectural metal roofing ..Roofing installer purchases unformed sheet metal stock. Panels are custom-formed to the required shapes.
Metal roof panels
type of architectural metal roofing.. Sometimes they consist of simpler corrugated or folded shapes fastened with exposed screws and rubber washers. Generally less expensive than custom-formed sheet metal roofing.▫
SIX OVER SIX
typical double-hung window had upper and lower sashes divided into six lights each; referred to as
Slip forming
useful for tall-walled structures. A ring of formwork is pulled steadily up by jacks supported on the vertical reinforcing bars. to reduce the need for framework in concrete construction
Lift-slab construction
virtually eliminates formwork for concrete constructuion
types of window frames
wood, aluminum, Plastic/Vinyl Window Frames (account for more than half of all windows sold in US residential market), steel
silica fume (pozzolan)
• *Silica fume* (also known as microsilica)- Produces extremely high-strength concrete that also has very low permeability.
Expanded shale aggregate
• *Structural lightweight* aggregates are made from minerals such as shale. Concrete made from *expanded shale aggregate* has a density about 20% less than that of normal concrete but is nearly as strong.
Disadvantages of light gauge steel framing
• *Thermal conductivity* of light gauge steel framing members is much *higher* than that of wood. • In cold regions, steel framing should be detailed with *thermal breaks*. These are materials with high resistance to the flow of heat, such as foam plastic sheathing or insulating edge spacers between studs and sheathing. Thermal breaks are designed to prevent the rapid loss of heat through the steel members. • Without thermal breaks, the thermal performance of wall or roof is greatly reduced, energy losses increase substantially, and moisture condensation within the framing cavity or on interior building surfaces may occur. • This may damage materials or encourage growth of mold and mildew.
Pouring and Finishing the Slab on Grade: bleed water, trowel, Shake-on hardeners, broom finish, superflat floors
• 1 st 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. • 2 nd step is the initial *floating*, usually by hand using flat-surfaced *bull floats*. These flatten and consolidate the surface. • For smoother surface, additional operations proceed as *bleed water* evaporates from the surface of the slab. ▫ • For completely smooth, dense surface, slab must also be *troweled*. This is done by hand using smooth rectangular *steel trowel or with a rotary power* trowel. • If nonslip surface is required, a stiff-bristled janitor's pushbroom is drawn across the surface of the slab after troweling to produce a striated texture called a *broom finish* -*Shake-on hardeners* These dry powders react with concrete to form a very hard, durable surface for heavy-wear applications like warehouses and factories. • (not concrete floors are perfectly flat) but*Superflat floors* are specified according to a more complicated system of index numbers called *F-numbers*. Floors are leveled using laser-guided automatic straightedging machines.
percentage of steel that is recycled or reused?
• 95% or more of all structural steel used in North American building construction is eventually recycled or reused, which is a very high rate
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.
Two-Way Slab Action
• A structural economy unique to concrete frames is realized through the use of *two-way action* in floor and roof slabs. • Works best for *bays that are square or nearly square.* • Use less reinforcing steel. • Cost less. ▫ Are reinforced equally in both directions and share the bending forces equally between the two direction
Concrete cover
• ACI 318-99, "Building Code Recommendations for Structural Concrete," requires *• 1.5 inches minimum cover for #5 rebars and smaller when formed concrete surfaces will be exposed to weather • 2 inches for #6 through #18 bars. • 3 inches when concrete is against and permanently exposed to earth. * • Bushhammering of architectural concrete will remove about 3/16 inch of cover, which needs to be considered during placement of the bars.
water for making cement
• ASTM standard C1602 defines the requirements for mixing water for concrete. • Must be free of harmful substances, especially organic material, clay, and salts such as chlorides and sulfates. • Water that is suitable for drinking has traditionally been considered suitable for making concrete. -More water increases workability but decreases strength.
define: Stainless steel
• Addition of nickel and chromium provides greater corrosion resistance • Costs significantly more than conventional structural steel
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.
Vertical bars ( for reinforcing concrete columns)
• Arranged either in a circular or rectangular pattern. • 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.
2 types of connections for bolts (steel)
• 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) and Tightened to the point that friction between the joined members strengthens the join Bolts are stressed in tension. Used where small changes in alignment can be detrimental to performance: column splices, beam-to-column connections, etc.
All about curing da 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.
Bracing and Bridging in Light gauge steel construction & web stiffeners
• 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. • 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
All about bolts (steel)
• Bolt holes typically 1/16 inch larger than diameter of the bolt. • Washers may be required to prevent damage such as galling* (tearing) of the surfaces of the joined members. • Bolts are usually tightened using pneumatic or electric impact wrench*
one-way concrete joist system, also called a ribbed slab. ( one way solid slab concrete)
• 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. • Stirrups are not usually used in concrete joists because of the restricted space in the narrow joist. • Joists are formed with metal or plastic pans supported on a temporary plywood deck One-way concrete joists are usually supported on *joist bands*, which are broad beams that are only as deep as the joists.
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 • Fireproofing of steel framing was originally done by encasing steel beams and columns in brick masonry or poured concrete. Added weight. NOw we add gypsum or spray on etier fiber or cementious mixture
Welding (steel)
• Can join members of a steel frame as if they were a monolithic whole. • Welded connections, properly designed and executed, are stronger than the members they join in resisting both shear and moment forces. • Bolting is quick and easy for *field *connections* that need only resist shearing forces + can be accomplished under conditions or adverse weather or difficult physical access that would make welding impossible.
Carbon Content
• Carbon content is a crucial determinant of the properties of any ferrous (ironbased) metal: • Too much carbon makes a hard but brittle metal (like cast iron) • Too little carbon produces a malleable, relatively weak material (like wrought iron) • Properties of mild steel have been optimized for structural purposes by controlling the amounts of carbon and other elements
Concrete Stairs
• Concrete is poured in one operation, and the treads are tooled to a steel trowel finish.
transit mixed (concrete)
• 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
Making and placing of concrete
• 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. • Each load of transit-mixed concrete is delivered with a certificate from the batch plant that lists its ingredients and their proportions. • 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. ▫
Controlling Cracking in Concrete Slabs on Grade
• Concrete slabs are particularly prone to cracking. • 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.
ultra-high performance concretes (UHPCs)
• Concretes with compressive strengths as high as 30,000 psi (200 MPa) and exhibiting even usable tensile strength are called *ultra-high performance concretes (UHPCs)*.
Prestressed concrete and the two different ways
• Contains less concrete than reinforced members of equivalent strength. • 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. -doesnt cause cracks • Prestressing is accomplished in two different ways: pretensioning and posttensioning. ▫
Define: mild steel
• Contains less than three tenths of 1 percent carbon • Includes beneficial elements like manganese and silicon • Includes detrimental impurities like phosphorus, sulfur, oxygen, and nitrogen **used as ordinary structural steel
Define: Electric Arc Welding (steel)
• Electrical potential is established between steel pieces to be joined and a metal electrode. • Continuous arc is established, generating sufficient heat to melt localized area of the steel members. • Molten steel from electrode puddles and is drawn along seam.
a moisture barrier (or vapor retarder) for slab-on-grade concrete
• 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.
Handling and Placing of concrete, drochutes
• 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 • Segregation is prevented by depositing the concrete, fresh from the mixer, as close to its final position as possible. • 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.
American Institute of Steel Construction defines three types of beamto-column connections:
• Fully-Restrained (FR) Moment Connections - sufficiently rigid that the geometric angles between members will remain virtually unchanged under normal loading. Sometimes referred to as a "rigid" connection. • Partially-Restrained (PR) Moment Connections - not as rigid as FR connections, but still strong enough to stabilize a building frame. Sometimes referred to as "semirigid" connection. • Simple Connections - otherwise known as shear connections, considered capable of unrestrained rotation under normal loading with negligible moment-resisting capabilities.
what is the W-c ratio?
• 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
bolsters (cement)
• In a broad beam or slab, reinforcing bars are supported by long chairs called
Reinforcing a Continuous Concrete Beam
• In a continuous structure, bottom of beam is in tension at midspan and top of beam is in tension at supporting girders, columns, or walls -if not arranged with stirrups, top and bottom steel , the beam will undulate
Reinforcing a 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 • 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*. -Bars are most heavily stressed at the midpoint of the beam span, with progressively smaller amounts of stress toward each of the supports. • Diagonal forces are resisted by a series of *stirrups*. Stirrups are either open *U-stirrups* or *closed stirrup ties* which are full rectangular loops of steel that wrap all the way around the longitudinal bars.
air-entrained concrete
• In areas of the country that are subjected to freezing and thawing, the concrete should be air-entrained to resist flaking and scaling of the surface. If air-entrained concrete is not used, there will be subsequent damage to the surface.
two-way flat plate system ((Two-Way concrete Systems)
• In lightly loaded buildings, the slab need not be thickened over columns, making formwork extremely simple. Typical depths for this two-way flat plate system range from 5 to 12 inches.
12,000 psi reinforcing steel
• In structures with especially heavy reinforcing requirements,.
tilt up 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. Useful for single stories- reduces need for framework in concrete construction -Tilt-up is the most widely used of the innovative construction methods described here.
The making of steel
• Iron ore is mined or excavated, heated to high temperatures in a blast furnace. • Impurities are separated out of the molten iron, and new metallic elements are added to adjust the composition for specific properties. • *Beam blanks* or blooms are made, which are then shaped. ▫
Define: composite metal decking & shear studs
• Is designed to work together with concrete topping to make a stiff, lightweight, economical deck. *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.
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.
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. • A number of standard ASTM laboratory tests are used to assess the various qualities of aggregates.
Advantages and Disadvantages of Light Gauge Steel Framing (4)
• Many advantages similar to those of wood light frame construction: • Versatile and flexible • Requires only simple, inexpensive tools • furnishes internal cavities for utilities and insulation • Accepts an extremely wide range of exterior and interior finish materials ▫
Bolts (steel): the 2 types
• 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.
waffle slab or two-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.
advantages of sitecasting of concrete
• Mixing and pouring operations are highly mechanized, carried out at ground level, and in controlled and sheltered conditions. • Control of the quality of materials and workmanship is generally better than on the job site. • Cast in permanent forms made of steel, concrete, glass-fiber-reinforced plastic, or wood panels with smooth overlays. • Smooth overlays have excellent surface properties which are mirrored in the high-quality surfaces of the finished precast elements. • Forms are reused hundreds or thousands of time; formwork costs per unit of finished concrete are low.
how much of n. America uses SCM
• More than half of the concrete produced in North America uses SCMs (suppl. cementioius materials).
Steel Framing (3 types of connections)
• Most steel frame connections use angles, plates, or tees as transitional elements between the members being connected.
• Nonstructural lightweight concretes
• Nonstructural lightweight concretes are made for use in insulating roof toppings
slab bands and the two kinds of economy (on-way solid slab concrete)
• One-way solid slab spans are often supported, however, by beams that are several times as broad as they are deep. • Banded slab construction offers two kinds of economy: • Width of the slab band reduces the span of the slab, which can result in a reduced thickness for the slab and consequent savings for the concrete and reinforcing steel. • Reduced depth of the slab band allows for a reduction of the story height of the building, with attendant economies in columns, cladding, partitions, vertical runs of piping, ductwork, etc.
• Three fundamental ways of supporting precast slabs:
• Precast concrete skeleton • Precast loadbearing wall panels • Combination skeleton/loadbearing walls
History of metal
• Prior to beginning of 19th century, steel had little structural role in buildings except in connecting devices. • Plentiful, inexpensive steel first became available in the 1850s with the introduction of the Bessemer process: • 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. ▫
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.
All about 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.
Steel angles are used for
• 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
Four kinds of precast concrete
• 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 ▫
define 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.
steel reinforcing bars and their length
• 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
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 ▫
Flaking and scaling in concrete
• The water/cement ratio should be as low as possible to improve durability of the surface.
Making of portland cement (fine gray powder0
• 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. • After cooling, clinker is pulverized to a powder finer than flour. • Often a small amount of gypsum is added to act as a retarder during curing.
4 ways to verify proper tension achieved in slip-critical connections (steel):
• Turn-of-nut method • Load indicator washer or direct tension indicator (DTI) • Calibrated wrench method • Tension control belts + power-driven shear wrench
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.
Sitecast Posttensioned Framing Systems
• Used in beams, girders, and slabs, both one-way and two-way, to reduce member sizes, reduce deflection, and extend spanning capability. • Two-way flat plate structures are very commonly posttensioned
concrete topping
• Usually 2 inches thick • Bonds during curing to rough top of precast elements • Becomes working part of structural action of precast elements • Helps precast elements to act together as a structural unit rather than as individual planks • Conceals slight differences in camber • Can incorporate reinforcing bars if needed for structural continuity • Underfloor electrical conduits can be embedded in topping
Supplementary Cementitious Materials
• Various mineral products, called supplementary cementitious materials (SCMs), may be added to concrete mixtures as a substitute for some portion of the portland cement.
Reinforcing Concrete Columns (two types of reinforcing )
• Vertical bars (also called column bars) and • Ties
Casting a concrete wall: form ties,
• 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. -form ties, are small-diameter steel rods specially shaped to hold the formwork together under the pressure of wet concrete. These are inserted through holes provided in formwork panels. • After second side of the formwork is erected, *walers* and *braces* are added. • Forms are filled with concrete. • After a few days of curing, formwork is *stripped* from the wall. • Ends of form ties are twisted off and *form tie holes* are filled with grout. ▫
Stresses in a Concrete Beam
• When beam supports a load, compression side of beam is squeezed and tension side is stretched • When steel elongates or stretches under tension, concrete around it forms cracks that run from the edge of the beam to the horizontal plane in the beam, above which compressive forces occur. • Half the concrete in the beam is doing no useful work except to hold the steel in position and protect it from fire and corrosion. ▫
Wide-Module Concrete Joist System ( one way solid slab concrete)
• 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. •stirrups are generally required near the ends of each joist.
Concrete Creep (concrete)
• 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.
Fabrication and Erection of Reinforcing Bars
• 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.
"w" type low-alloy reinforcing steel
• Where concrete must meet special seismic design criteria or where extensive welding of reinforcing is required, low-alloy steel meeting special ductility requirements is used. This steel meets ASTM A706, and is designated as "W" type low-alloy steel.
high stregth reinforcing bars
• 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. ▫
• Workability agents
• Workability agents improve plasticity of wet concrete to make it easier to place in forms and finish. They include pozzolans and air-entraining admixtures, along with fly ashes and organic compounds.