COSC 253 Exam 3 Simms

Wide Flange

- W shape - most commonly used shape in beams and columns - greater web depth for longer span

Riveting

- White hot fastener is inserted through holes to be fastened - fastener is hammered to produce a head on the plain end - metal cools and contracts tightly clamping steel members -rarely used today, mostly in historic structures

Stabilizing (Bracing) the Building Frame

- framing accessories: various sheet metal, stiffeners, bracing hangers used - rectangular geometry of the building frame must resist lateral forces - braced frames, shear walls and moment resisting frames

Architectural sheet metal roofing

- Less expensive aluminum or steel sheets are factory-coated for greater color choice and longevity - aluminum - metalic coated steel - plain steel

Mini-Mills

- Most US steel is made from recycled steel scrap here - steel scrap is converted directly to new steel using electric arc furnaces Pros: less expensive to build, high quality low cost, use less energy, 90%+ recycled content, in North America, almost all hot-rolled structural steel shapes are made from recycled steel here

Mild Steel (Low carbon steel)

- Most common alloy for modern structural steel - Not more than 0.3% carbon - Small amounts of other metals improve strength, toughness, and other qualities - Reasonably strong, highly ductile, and easily welded - Equally strong in tension and compression

Thermoset Membranes

- Most common type is ethylene propylene diene monomer (EPDM). - Synthetic rubber. - Highly resistant to the effects of heat, UV radiation, and weather.

Thermoplastic membranes

- PVC: high performanmce but with environmental and health concerns in manufacturing and disposal - TPO - more recently introduced membrane material, good chemical stability, heat weldable

Welding

- Steel surfaces to be joined are heated to a molten state - molten metal is added from the electrode - at finished joint, members are fully fused

info on steep roofs

- roof with a pitch of 2:12 (17%) or greater is considered steep roof - materials are classified by fire resistance (A,B,C) in decreasing order of resistance - cool roofing materials on steep roofs save 5-10% on building cooling costs

Roles in construction process

- rough sketch (architect) - sketch progresses into finished set of structural drawings (structural engineer) - structural drawings are used to prepare detailed shop drawings (fabricator)

Ways to join light gauge steel framing members

- self-drilling, self tapping screws are the most common - crimping tools manually deform parts to be joined - nail like pins are power driving

Joining Metal Roofing

- soldering (flat-seam) - exposed fastener - connected fastener

Coped Beam to Girder Connection

- steal beam to girder connection - top flanges of beam are coped (cut away) to allow the tops of a beam and girder to be set level

Wood shakes

- thicker than shingles exhibit a rougher texture - Usually split rather than sawn - may be tapered or uniform thickness "Straight") - Length: 18 and 24 inches

Materials used on steep roofs

- wood shingles - wood shales - asphalt composition shingles - mineral surface roll roofing - slate shingles - clay tiles - sheet metal

Moment connections

-Beam flanges are joined to column -transfers gravity (shear) loads and bending forces to column -Column may be reinforced with stiffener plates to carry bending forces - welds join top and bottom beam flanges to column and reinforcing plates - creates continuous beam condition that transmits bending forces

Steel decking

-Corrugated Steel decking laid over the framing is the most common floor and roof decking material - decking is puddle welded to framing members below - comes in a variety of profiles, depths to suit load span considerations - Deformations allow structural bond between deck and concrete poured over it, to increase the strength of the deck/ concrete floor assembly

Traditional Mills

-Iron ore is processed into molten iron in a blast furnace, then converted to steel - 25%-35% recycled - Primary products: flat-rolled stock such as steel decking and other sheet products

Other shingle materials

-Sheet metal (can mimic slate) -Rubber -Fiber-reinforced cement -Plastic

Built-up Roof (BUR)

A roof membrane laminated from layers of asphalt-saturated felt or other fabric, bonded together with bitumen or pitch.

single ply roof membrane

A sheet of plastic or synthetic rubber used as a membrane for a low-slope roof. - less onsite labor - reinforced with glass or plastic fibers or mesh for greater strength - wide range of colors - elastic and less prone to cracking with age - membranes may be mechanically fastened (screws), glued, or ballasted with gravel or concrete pavers - thickness (MILS)

Fire protection of steel framing

Active: system that requires some type of action in order to work in a fire event (sprinkler system) Passive: utilizes fire-resistant construction to limit spread of fire to protect structural members (no action) (concrete encased, plaster covered, gypsum board enclosed, Spray Applied Fire Resistant Material (SFRM) , loose insulation within column cover, concrete filled

Test Question

Anchor bolts stick up out of concrete, fine tuning column. level with "leveling nuts" at the base plate of a column

Wood shingles

Are thin, tapered slabs of wood that are sawn from pieces of a tree trunk Lengths: 16,18, and 24 inches

Insulating low slope roofs (above the roof membrane: Protected Membrane Roof (PMR))

pro: membrane is protected from outdoor temps and immune to moisture blistering problems, Aggregate ("ballast"), pavers, or other material hold it down and protect it from sunlight/physical wear Con: membrane repair are more costly

Insulating low slope roofs (between structural deck and roof membrane: Traditional)

pro: protects deck from outdoor temperatures con: risk is accumulation of moisture within the insulation

Insulating low slope roofs (below structural deck)

pro: relatively economical and trouble-free Con: leaves roof deck and membrane exposed to full outdoor conditions

Groove Welds

require properly shaped and spaced joints

Shingles

small overlapping roofing units with staggered vertical joints made of wood, asphalt, slate, clay, concrete, metal, and other materials

Shear studs

welded to tops of beams, through metal decking . Once concrete is poured, the beams, decking, and concrete act together structurally

Testing of welds

welds critical to structural stability are inspected/tested (ultrasonic, magnetic, etc.) to ensure soundness and freedom from flaws

Bolts

Carbon steel bolts - relatively low strength, limited uses, fastening light frame elements and holding temp connections, also called common/unfinished bolts High strength bolts - stronger than common bolts, used for fastening primary structural members, heat treated for tensile strength

topping-out ceremony

Ceremony when the "last beam" is set on top of the building

Cold-worked (formed) steel

Deforming steel in its cold state causes realignment of steel crystals and increases its strength

Pros/cons of steep roofs

Drains quick, little chance for leak, visual appeal, simple repairs, manufactured materials in small units, many options

Fillet welds

Easy to make, little joint preparation required

Puddle welds

Fasten metal decking to structural members

Channels, Tees, Angles

For trusses, lighter weight framing, and other miscellaneous uses

Thermal bridging and insulating light gauge steel

Thermal bridging - continuous insulation installed across metal stud cavities will increase thermal performance Insulating light gauge steel framing - Light-gauge steel framed (LSF) wall systems are made of cold-formed steel studs and tracks and lined with gypsum plasterboards. Mostly cavity insulated for acoustic and thermal performance. Cavity insulation delays temp rise across wall as it restrains heat transfer

Asphalt or Composition Shingles

They're cut from heavy, asphalt impregnated fiberglass or cellulosic felts. Surface mineral granules protect from UV degradation and abrasion. Installed over solid sheathing and underlayment of asphalt-saturated felts or synthetic membranes. Roofing underlayment and shingles (of all types) are generally installed starting from the eaves and working up the slope of the roof, to achieve an overlapping that naturally sheds water off the roof. Moderate fire resistance and last 15-25 years.

Bolt Tensioning

Turn-of-nut method: nut is tightened 1/3 a turn past snug Load indicator washers: when bolt is adequately tensioned, protrusions on the water are flattened, some indicator washers squirt dye Calibrated wrench: torque wrench used to tighten bolts, not used frequently

Light gauge steel framing and the building code

Type 1 and 2 - Light gauge steel (cold-formed steel and cold-rolled steel) is a cold-formed material that is used to make construction processes smoother and products stronger - not bulky like structural steel - not heavy like concrete - similar to wood frame construction in principle - wooden framing members are replaced with thin steel sections coated with zinc (galvanized) or a mix of zinc and aluminum (zincalume or galvalume) to protect from corrosion

Carbon in steel

added to iron to make it harder and brittle steel with low carbon is more malleable

Standard nomenclature for light gauge steel framing 9/10

- depth - width - type - thickness of sheet metal used to fabricate steel framing member Example: "600s162-54" - 6.00 inches deep - S = Stud or joist - 162: 1.625 (1-5/8) inches wide - 54: 54 mils sheet metal thickness

Types of Light Gauge Steel Framing Members

Studs and joists, Tracks, Channels, Furring, L-headers, Special products (slip tracks, jamb studs, etc.)

HSS (Hollow Structural Section)

"HSS 8x8x1/2" - 8"x8"x1/2" wall thickness - hollow square, rectangular, round, and elliptical shapes - cold or hot-forming steel strip (sheet) and welding longitudinally - suitable for structural members subject to twisting or buckling stresses - used for trusses, structural column sections, and where simple external profile is desirable

L angles

"L4x3x3/8" - 4" x 3" nominal legs - with 3/8" thickness

Wide-Flange Shape Designation

"W10 x 30" - W = wide flange shape - 10 = nominal depth in inches - 30 = Weight in pounds per lineal foot - by varying roller size and spacing, various weights can be produced, all nominally 10" in depth

WT: T-shape cut from a W-shape

"WT 13.5x47" - 13.5"depth of web x 47 lb/ft - Produced by cutting a W27x94 lengthwise in half

Why steel fire protection

- above 500-600 degrees, steel rapidly loses strength - at about 1,600 degrees, it loses all strength - fireproofing acts as insulation, protecting steel from heat of fire

Flat-seam metal roofing

- attatchment cleats nailed to decking and rolled into the flat pan seams - minimum recommended slope - 3:12

Roof Membranes

- bituminous - single-ply - fluid-applied

slip-critical connection

- bolt is tensioned to such an extent that movement in the joint is resisted by friction between the members themselves - bolt is very highly stressed but in tension - no slippage, bolts tightened to 70% of their strength - used where joints experience load reversals, high stressed joints, or where slippage would be detrimental (column splices in tall buildings)

bearing-type connection

- bolts only need to be installed in a snug tight condition - body of bolt resists movement between connected members by bearing against sides of bolt holes - shear stress - connection will slip before reaching full strength

Column to Column Connection

- column splices typically at waist height to avoid interference with beam-column connections - where outer dimensions of connected columns differ, a butt plate or bearing plate is added to the connections

shear connection

- joins only the web of the beam to column flange - transfers gravity (shear) loads from beam to column - not sufficiently rigid to transfer bending forces (bending moment)

Structural Steel

- less than 2% carbon - strong in tension and compression - Ductile (not prone to sudden failure)

Sheet metal roofing

- made from various sheets of metal - lead - copper - lead-coated copper - zinc coated steel - stainless steel

Slate Shingles

- relatively inexpensive - kiln-dried clay or cast concrete - glazed or unglazed - fire-resistant - 30-75 years

Steel Construction process

1. Rough sketch (architect) are completed, submitted to(structural engineer)for review and approval 2. Fabricator (shop drawings approved by architect and structural engineer), orders material and steel members are prepared (cut, welded, fabricated) 3. Erector (may or may not be same as fabricator) assembles structural steel members after they are delivered to the site

Bessemer Steel Process

Late 1800s Invented by WIlliam Kelly and Henry Bessemer Allowed steel to be manufactured cheaply

Pros/cons of light gauge steel framing

Pros: - strong/lightweight - non-combustible making it the solution in certain construction - dimensionally stable and precise - wide variety of finish materials Cons: - members can require more frequent bracing - conducts heat and requires extra attention to thermal bridging - susceptible to corrosion

Uniqueness of steel as a building material

Pros: affordable, available, rapid construction, strength, durability, recyclable Cons: loses strength in fires, prone to corrosion

Pros/cons low slope roof

Pros: cover a building of any dimension, simple and cheap construction, can serve as decks, patios, or parks "Green roofs" Cons: water drains slower, membranes must be perfectly sealed, membrane materials are limited

Weld symbol

Provides info on type, size, location, and if weld is being performed in the field, flag symbol means field, circle around means both sides are welded. Weld is on opposite side of arrow when on top, same side of arrow when below

Modified Bitumen

SBS (Styrene,Butadiene,Styrene), APP (Actactic, Polypropylene), Sheets of factory manufactured polymer modified bitumens, Reinforced with plastic or glass fibers for greater elasticity and durability - Also called "Mod-bit" roof, Overlapping plies by torching it (heat welding) - hot applied, there is also peel n stick (self-adhered), Mod-Bit membranes must be protected from UV exposure, Aggregate granules or aluminum emulsion liquid coating can be Summary: broadly availabe, redundency in layers, physically tough, suitable for wide range of cost/durability requirements

Crickets and saddles

locally sloped surfaces used to divert water around obstructions in the roof or create slope in level areas

Low slope roof

minimum slope of 1/4" per foor (2%) incline required by building code for low-slope roof membranes - primary and secondary (emergency) drains - secondary drains include elevated roof drains or scuppers

OWSJ

open web steel joist, mass produced steel trusses to support floors and roofs