Steel Flashcards
<p>Types of steel</p>
<p>steel advantages = high strength + ductility, ease/speed/precision</p>
<p>disadvantages = melts when heated, will corrode</p>
<p>low carbon steel = .06-.3%</p>
<p>medium carbon = .3-.5%</p>
<p>high carbon = .5-.8%</p>
<p>as carbon increases, strength increases, but ductility decreases, so medium is 'best'</p>
<p>weathering steel = corten/has copper added to form patina</p>
<p>A36/A992 = common in W shapes (.25-.29 carbon)</p>
<p>A440 = high strength, for bolting, riveting</p>
<p>A441 = low alloy for welding</p>
<p>Ornamental metals</p>
<p>handrails, guardrails, elevator interiors, metal panels, door/partition facings, signs, light fixtures, ceilings, meshes and perforations,Âetc.Â</p>
<p>most common: SS, Cu alloys, bronze, brass, Al</p>
<p>less common: carbon steel, Cu, iron, porcelain enamel</p>
<p>10 gauge min. in lg. sheets to avoid oil canning, unless back laminated, or embossed</p>
<p>Metal fabrications</p>
<p>non-structural, like stairs, expansion jts. (both structural and seismic), gratings, ladders, etc.Â</p>
<p>Types of stainless steel</p>
<p>302: Cr, Ni added, very strong, hard corrosion resistant</p>
<p>304: like 302, but more weldable, commonly used</p>
<p>301: less Cr, Ni, better tensile strength</p>
<p>316: for extremely corrosive environments</p>
<p>430: no Ni, less corrosion resistance, interiors only</p>
<p>W_x_</p>
<p>nominal depth x weight lbm/ft</p>
<p>Cast iron first reasonable</p>
<p>1709, Abraham Darby used coke not charcoal in production, decreased impurities, increased strength</p>
<p>Steel first reasonable</p>
<p>1856 Henry Bessamer process makes steel inexpensive, stronger</p>
<p>Types of Steel Shapes</p>
<p>wide flanges (W), I-beams (S), channels (C), structural tees (WT or ST), angles (L), tubes (TS) - round/square/rectangle, plates (PL) (more than 6"), bars (less than 6")</p>
<p>Non-ferrous metals</p>
<p>Al: soft, so alloyed w Mn, Zn, Mg, Cu, usu. extruded, high stength to wt., but high embd. energy</p>
<p>Cu: very non-corrosive bc of patina (oil or wax can slow this process), v. conductive, used for wiring, pipes, ornament</p>
<p>Bronze: Cu + Sn</p>
<p>Brass: Cu + Zn</p>
<p>Zn: non corrosive, for roofing/flashing</p>
<p>Pb: good acoustics, easy to form, non-corrosive, poisonous</p>
<p>Types of metal decking</p>
<p>Most often steel, sometimes aluminum; composites ats structurally with concrete infill; cellular allows raceways</p>
<p>Metal finishing</p>
<p>bending, brake forming, spinning, embossing</p>
<p>annealing = reheated + slowly cooled to make more ductile</p>
<p>quenching = reheated + cooled quickly in water to strengthen</p>
<p>tempering = reheated + medium coolest to strengthen + increase ductility</p>
<p>case hardening = harder surface, softer core</p>
<p>anodizing = electrolytic bath that does surface chemistry to help corrosion resistance</p>
<p>painting/coating = for protection or aesthetics</p>
<p>Steel channels used for:</p>
<p>framing openings, stringers, where flush side is needed - buckle easily bc of asymmetry</p>
<p>Light gauge metal framing</p>
<p>10-25 gauge; usu galv. steel, sometimes aluminum; used for interior partions, exterior walls (bearing or non), joist, rafters, etc.; NONCOMBUSTIBLE; doesn't shrink with ageÂ</p>
<p>Cast iron common</p>
<p>1876, used in roofs in France</p>
<p>1850-1880 = Cast Iron Age</p>
<p>Levels of metal finish</p>
<p>No. 3 = dull, coarse</p>
<p>No. 4 = general purpose, still dull/coarse, common</p>
<p>No. 6 = sull satin</p>
<p>No. 7 = reflective</p>
<p>No. 8 = mirror-like</p>
<p>Cast iron showcased</p>
<p>1851; Crystal Palace, Joseph Paxton</p>
<p>1889; Eiffel Tower, Halle des Machines</p>
<p>Open-web steel joists</p>
<p>bottom chord & webs = bent rods</p>
<p>top chord = angles w/ bearing plate attached</p>
<p>Types of open-web steel joists</p>
<p>K-series (2" increments) (spans 8-60 ft), LH-series (4" incr.) (spans 25-96 ft), DLH-series (4") (spans 89-144 ft), e.g. 36LH13 (36" depth, LH-series, type 13 chord). Chord number increases as strength increases.</p>
<p>Metal fabrication types</p>
<p>casting (molds), hot rollingÂ(W-shapes, finer, less strong, more flexible), cold rolling (stronger, more brittle), extruding, drawing (stronger)</p>
<p>Galvanic Action Index</p>
<p>Most reactive metals: Mg, Zn, Al, Mild Steel, Cast Iron</p>
<p>Medium: Cu, Ni, Cr, Pb, Sn, Stainless Steel (active)</p>
<p>Least reactive: Brass, Bronze, Stainless Steel (passive)</p>
<p>Types of iron</p>
<p>wrought = low carbon, has slag, soft/ductile, corrosion resistant</p>
<p>cast = ~2% carbon, hard & brittle</p>
<p>grey cast iron = high silicon content, for plumbing uses</p>
<p>Cast iron + Steel = 1st skyscraper</p>
<p>1885, cast iron int/ext cols., Bessamer girders, William LeBaron Jenny, 10-story, Home Insurance Bldg., Chicago</p>
<p>Cast iron first used in buildings</p>
<p>By 1779, common in bridges and columns</p>
<p>Metal joining</p>
<p>bolts, screws, welding (>800 deg F), brazing (800-500 deg F - only filler melts), soldering (used for lower melting pt. metals, only filler melts)</p>
<p>Why gauge doesn't matter</p>
<p>proprietary, different ones, too confusing, go with actual dimensions, not nominal</p>
<p>Metal processing</p>
<p>smelting = refining</p>
<p>alloying = adding different metals to main metal to confer good properties</p>
<p>Â</p>
<p></p>
<p></p>
Thickness: 22 ga steel
0.0336 in
Thickness: 20 ga steel
0.0396 in
Thickness: 18 ga steel
0.0516 in
which is strongest? Hot or cold rolled steel
Cold rolled steel
Stiffener plates
Welded on to make more rigid up the web at the point where extra forces are going to be applied
Back up bars
Prevent welding arc from burning through the flange
How are steel elements attached
Welding or bolts
Steel column baseplate
Distribute the load of steel columns on concrete foundations
Dog bone cuts
Control valve for seismic for es, deforming so that there is not a catastrophic failure of the welded or bolted joint
Eccentrically braced frame
Useful in seismic loads as it resists lateral seismic forces without buckling
Shear wall
Provides lateral stability by preventing lateral forces from collapsing the structure
Staggered truss system
Every other floor is a truss - minimizes the thickness of the slab and the number of columns and floor to floor height
Shear stud
Floor element welded to steel beam used to rigidly attached flooring (concrete) directly to beam
Girts
Metal channels that span between steel columns - they receive the cladding and hold it in place
Fireproofing steel columns (6)
NAME?
Fireproofing steel beams and girders (6)
NAME?
Castellated beam
Improved beam produced by flame cutting the web of a wide flange section along a zigzag path then reassembling the beam by welding its two halves point to point thus increasing its depth without increasing its weight
Washers
Used to prevent galling (wearing between bolt and beam)
Shear vs moment
Shear:Flanges aren’t engagedMoment:More rigidMore expensive
Open web steel joists/trusses (3)
K series: standard 8-60ft long and 8-30in deepLH series: long span 25-96ft long and 18-48in deepDLH series: deep long span 89-144ft long and 52-96in deep
Bearing type bolt vsSlip critical bolt
Slip critical slightly deforms the steel, creating tension and not allowing any movement Bearing type bolt it rests on the bolt, some movement allowed
Components of concrete
Cement (portland cement), aggregates and water
Difference between prestressed, pre-tensioned, and post-tensioned?
Prestressted: squeezing concrete together; categoryIt can be pretensioned or posttensionedPre-tension: precastPost-tensione: cast in place; pull draped cable with hydraulic
Components of concrete
Cement (portland cement), aggregates and water
Difference between prestressed, pre-tensioned, and post-tensioned?
Prestressted: squeezing concrete together; categoryIt can be pretensioned or posttensionedPre-tension: precast; cable or wire is draped then concrete poured, then cable is cut so that the resulting compressive force is teansferred to the concretePost-tensione: cast in place; pull draped cable with hydraulic
Types of Portland Cement
Type I: normal concreteType IA: air entrainedType II: concrete with moderate resistance to sulfates and used when the groundwater or aggregate contains sulfatesType IIAType III: high early strenght (precast)Type III AType IV: low heat of hydration (massive structures)Type V: high resistance to sulfates
size of aggregates
less than 3/4 space between rebar and less than 1/3 depth of slab
why use lightweight aggregates
lighter weight or higher therman resistance (better insulation)
range of concrete strength
2,000 psi to 20,000 psi
concrete strength test
slump test: measures consistency of concreteconcrete cylinders (lab testing): measures compressive strength
how are reinforcing bars measured
in 1/8 in
what do chairs do
they keep the rebar at the right height when the concrete slab is poured
what is shrinkage-temperature steel
steel wire reinforcing in concrete slabs that runs perpedicular to the lenght of the slab
what do vertical bars do
take up vertical compression loads and tensile loads on the column
what do column ties do
prevent outward buckling
what does fibrous reinforcing in concrete do and what are the types
types: microfiber and macrofiberthe fibers act as tension members during curing
prestressing
squeeze the concrete to increase its strength
slab on grade steps
- scrape top soil2. add crushed stone3. roll out plastic sheeting4. place formwork leveled top5. place welded wire or rebar on chairs6. pour slab7. screed the slab8. give slab floating9. trowel the surface for smooth10. cover surface to keep damp11. create control joints
how to minimize need for control joints
use stronger concrete, fly ash concrete, admixtures (less shrinkage), post tension, or microfibers
control vs isolation joint
control joint extends partway down the depth of the slab to limit crackingisolation joint extends all the way through the slab to resist expansion and contraction, seismic forces, for noise or vibration, or to break up irregular shapes
ICF (insulated concrete forms)
serve as concrete formwork and provide insulation - polysterene foam forms that remain in place after the concrete cures
shores
adjustable height columns used to support the beams of a slab that is not poured on grade
distribution ribs
added at the midspan of the joist in a one-way joist system to provide more rigidity and distribute the loads more efficiently
drop panels
in a two way flat slab their job is to resist the shear forces near the top of each column, especially if there is a seismic or wind load that imparts a lateral force
heads in waffle slab
resist the shear forces near the top of each column, especially if there is a seismic or wind load that imparts a lateral force
lift slab system
cast all floor and roof slabs in a stack at the ground on the columns, lift them to the proper heights with a hydraulic jack and weld them into place - no formwork
flying formwork
it uses large sections of reusable formwork (typ supported on metal trusses) which a crane lifts into place where the slab is poured. Then the formwork can be raised to the next level
double tee
precast structure containing high strength pressure cables
welded wire fabric
cold drawn steel wires set at right angles with each other and welded at the intersections
concrete admixtures
NAME?
fly ash
waste material obtained from coal fired power plants - imporves workability, reduces temperature rise, minimizes bleeding, reduces permeability, enhances sulfate resistance
architectural concrete finishes
form lines. scrubbed, acid wash, water jet
tooled and sandblasted finishes
bush hammering, grinding, applied, applied, sandblasted finishes
rubbed finishes
smooth and grout cleaned
concrete slab finishes
float finish, light steel troweled finish, hard steel troweled finish, broom finish
expansion joint
allows entire sections of a concrete structure to move independently
