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197 Cards in this Set
- Front
- Back
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How sturdy is wood in tension and compression?
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Near equal resistance in tension and compression.
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What are the two categories of wood?
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1. Softwood
2. Hardwood |
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Types of Softwood trees-
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(conifers) Spruce, pine, fur, etc. Evergreen all year round.
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Types of Hardwood trees-
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(Deciduous) Poplar, aspen, cottonwood etc. Looses leaves in fall
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Ranking of Structural strength (Visually graded) for wood-
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select structural
No.1 No.2 No.3 Stud Construction Utility |
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What are the two types of rankings for wood strength?
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Visually graded and Machine-stress rated
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Machine-stress rated for wood-
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you can get an accurate rating instead of visual rating
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What are the three size classifications for wood?
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Dimension lumber
timbers Decking |
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Dimension Lumber (wood)
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(2" to 4") used for light framing, light construction.
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Timbers (wood)
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(5"+) Beams, posts and timbers, used for heavier beam members.
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Decking (wood)
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(2" to 4") used for the floor and roof
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Anisotropic (wood)-
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properties arent the same everywhere. strength is greater along the grain instead of perpendicular to it.
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What are the five properties of anisotropic for wood?
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1. grain
2. density 3. knots 4. reaction wood 5. shrinkage |
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What is the structural strength of wood GRAIN?
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Strength is greater along the fibers (parallel to the grain) than perpendicular to the grain.
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What is the structural strength of wood DENSITY?
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Earlywood and Latewood. The most dense wood is Red Oak.
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What is the structural strength of wood KNOTS?
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If a knot is firm then it isnt problematic but if its loose then it could fall out.
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What is Reaction Wood?
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Grown in a compression or tension zone. A tree that grows not straight up. tends to have a bow or crook, it can also cause the wood to twist.
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What is wood shrinkage?
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max tangential to the grain, 50% less radial to grain. Longitudinally we have very little shrinkage.
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What is Load Duration?
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Wood can cary greater loads for short durations than for longer durations.
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What is Wet Service?
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High Moisture content dramatically reduces strength.
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What is temperature for wood?
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Heating decreases wood strength (up to 150 degrees F the effect is reversible) Really hot temperatures isn't good to use wood.
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What is the deformability of wood?
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-Elastic and Proportional to loading
-Plastic and increases as failure approaches - Failure due to compression: Traverse bulging (not abrupt) - Failure due to tension: abrupt (Under compression wood will fail ductility) |
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How durable is wood?
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Wood is prone to decay and termite attacks.
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What ways can you control Moisture in wood?
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Moisture barriers and membranes
Ventilation on cold side |
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Moisture barriers and membranes for wood-
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eaves or soffit vent should be continuous or consist of evenly distributed openings.
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What are three ways to protect wood?
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-painting
-wood preservatives (Redwood doesnt seem to rot as much as cedar) -pressure treated (can soak it in tar) |
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How combustible is wood?
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Very, problems with fire and has an effect on insurance rates.
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Building codes for wood-
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the allowable area you can build wood is smaller than other material (limited to small buildings and houses)
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What is charring?
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WHEN HEAVY TIMBER EXPOSED TO FIRE REACHES TEMPERATURES AROUND 1000 TO 2000 DEGREES FAHRENHEIT THE SURFACE CHARS CREATING A PROTECTIVE LAYER THAT RETARDS COMBUSTION AND PROTECTS THE WOOD CORE.
-WOOD SPECIES CAN BE ASSIGNED CHAR RATES OR THICKNESS OF CHARRED SECTION FORMED PER MINUTE AT A GIVEN TEMPERATURE. -SOLID TIMBER/GLULAM: 1/40” PER MINUTE. |
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What are wood joists?
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(Normal maximum span 20) Lightly, closely spaced members that span between beams or bearing walls.
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What are Wood Joists?
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Lightly, closely spaced members that span between beams or bearing wals. (normal maximum span: 20)
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What are the typical sizes of wood joists?
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2" X 6"
2" X 8" 2" X 10" 2" X 12" |
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What are solid Wood Beams?
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(plank and beam construction) Members of 4" or 6" nominal with span between grinders or bearing walls at spacings of 4', 6' or 8'. Economical span 10 to 20 ft. Solid or laminate wood decking is used to span between the beams with the underside of the decking being the finished ceiling.
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What are Glued Laminated Construction?
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Made up of individual pieces of lumber 3/4" or 1-1/2" thick glued together in a factory. Standard width: 3-1/8", 5-1/8", 6-3/4" and 8-3/4". Normal span range is 15" to 60" beams.
- Because individual pieces can be selected free from certain defects and seasoned to the proper moisture content and the entire manufacturing process is conducted under carefully controlled conditions the allowable stresses for glue lam construction are higher than for solid sawn lumber. Although glue lam beams are usually loaded in the direction perpendicular to the laminations they can be loaded in either direction to suit the requirements of design. |
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What are the three appearance grades glue-lam beams?
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1. Industrial- used where appearance is not a primary concern
2. architectural- used where appearance is a factor but the best grade is not required. 3. Premium- used where the finest appearance is required. |
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What are Light weight I Shape Joists?
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consist of a top and bottom chord of soild or laminated construction separated by a plywood web. Better dimensional stability than solid wood construction.
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What is the typical span range of Light weight I Shaped joists?
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24 to 48 feet (60' on special order)
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What are wood trusses?
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made up of standard size wood members connected with metal plates. Typical span range is 24 to 40 feet. Typical depth is 12" to 36". Common spacing is 24" O.C.
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What is a plywood box beam?
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Plywood panels are glued and nailed to soild wood members (usually 2 X 4 framing). Box beams are normally designed specifically for each job and assembled at the site. Allows wires and services can be run inside the void giving the member a cleaner finish. Torsional rigidity.
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What is stress skin panels?
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Horizontally, glue and screw 2 plywoods to strut. typical max span is 32 ft
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What are the 7 types of wood systems?
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- wood joists
-soild wood beams - glued laminated c onstruction - light weight I shaped joists - truss - plywood box beam - stressed skin panels. |
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What are the 4 types of wood connections?
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- joinery
-nails -bolts -glue laminations |
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What is joinery?
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When you try to make connections with wood (no nails) beam to beam connections ( tusk tenon and soffit tenon) a lot of intense labor bc a lot of carving
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What are the 3 types of nails?
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-box nails
-wire nails -common wire spikes |
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What are box nails?
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6 penny (6D) to 40 penny (40D)
length: 2-5 in. smallest diameter for a given size. |
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What are wire nails?
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6D to 60 D
Length 2-6 inches |
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What are common wire spikes?
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length 3-8-1/2 inches
largest diameter for a given size. |
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What is the strongest wood connections?
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Lateral load in side grain.
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What is the weakest wood connection?
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withdrawal from end grain
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What are the two types of screws?
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round and flat heads
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What are the two timber connections?
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-split ring(weakest) ring around the connection, half a ring in both pieces of wood.
-shear plates-ring on outside then ring of steel, reinforcing bolt. |
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What is the composition of steel?
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alloy of iron and carbon
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What is the composition of stainless steel?
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alloy of iron, carbon and nickle added.
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What are the grades of steel? (strength)
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ASTM A36: 36,000 PSI (yield point)
ASTM A441: 40,000 & 50,000 PSI ASTM A572: 42,000 & 50,000 PSI ASTM A588: 50,000 PSI |
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What is the allowable stresses for structural steel?
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allowable stresses for structureal steel are expressed as a fraction of the ield strress of the steel. They vary with the types of stress the member is nder (Shear, compression, bending, and tension) and with conditions such as supported lengths and geometry of the section.
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What are the more common code requirements for allowable stress are:
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tension on gross area= 0.6 X Yield stress
shear on gross area = 0.4 X yield stress bending = 0.66 X yield stress |
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What are the standard shapes of I- Beams?
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W
M S HP |
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What are standard shapes of steel?
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I beams
channels angels tees tubes pipes bars steel plates |
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What are the three ways to weather protect steel?
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stainless
weathering steel (corten) paint |
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What is stainless?
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(expensive) add hycolw to alloy of carbon.
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What is Weathering Steel (Corten)?
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it rusts but the 1st layer of rust keeps the rest from rusting.
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What is corrosion protection?
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Durable fluorocarbon paint. SHop-applied primer, undercoat and finish coat. Second finish coat applied in the field after erection of the steel frame.
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When does steel start to loose its strength (what temperature?)
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steel doesnt burn but at 600 F it starts to loose strength. complete structural loss at 1200 F.
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What are the 4 ways to fire protect steel?
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1. spray on fire protection (2nd floor stairwell in the arch building)
2. gypsum board-type X drywall 3. incase it in concrete. 4. sprinkling system |
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What is a steel beam and girder system?
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large members (girders) span between vertical supports and smaller beams are framed into them. Typical span range- 25' to 40'. Typical beam spacing- 8' to 10'
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What are the spans of open web steel joist?
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-standard open web joists- span: up to 60'. Depth: 8" to 30" in 2" increments.
-Long span joists- Span: up to 96' (deep long span: 144') Depth: 18" to 72". -Typical spacing- floor joists: 2' to 4'. Roof joists: 4' to 6'. |
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How do you connect steel together? (3 ways)
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1. Rivets
2. bolts 3. welding |
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What are rivets?
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doesnt loosen under vibration and for that reason they are used on highway bridges and railway bridges.
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What are the spacing for bolts?
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absolute minimum 2-2/3 times bolt diameter. Preferred: 3 times bolt diameter. Edge distance typically 1.25 times bolt diameter.
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What are the two types of bolts?
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-bearing type
-friction type |
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What is the bearing type of bolts?
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-shear resisted in the bolt
-lowest load-carrying capacity -used in non-critical or secondary connections |
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What is friction type of bolts?
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-bolt tightened to such an extent that friction develops between the connecting members and loads are transferred through friction rather than through the bolt itself.
-greatest load carrying capacity. |
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What is welding?
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the fusing of 2 materials (steel) together
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What are the advantages and disadvantages of welding?
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-Advantages:
+the gross cross section of the members can be used instead of the net section. +construction is often more efficient +Welding is more practical for moment connections. -Disadvantages +Members must be held in place until welding is complete. +Requires highly skilled labor. |
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What is a building foundation?
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part of the building that transmits all the gravity and lateral loads to the underlying soil. When the baring capacity is lower the foundation gets bigger.
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The design and selection of a building foundation depends on:
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-required strength of the foundation
-ability of the soil to sustain loads without excessive total settlement or differential settlement. |
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What are the 4 soil properties?
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1. unified soil classification system
2. subsurface exploration 3. bearing capacities 4. other considerations |
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What is unified soil classification system?
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this system divides soils into major divisions and subdivision based on grain size and laboratory tests of physical characteristics and provides standardized names and symbols.
** Doesnt give barring capacities! |
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What is the purpose and types or subsurface explorations?
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Purpose: to determine bearing capacity of the underlying soil through testing. it is the first step in designing foundations.
Types: -borings -test pits |
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What is the spacing and number of soil borings?
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-dependent on building size: min of one near each corner
-dependent on suspected subsurface geological conditions -typical spacing: 25 to 50' -typical depth: 20' to 30' (10' per story) |
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What is a standard penetration test (SPT)?
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-A SPT is a measure of the density of granular soils and the consistency of some clay soils (borehole test)
-procedure: a 2" diameter sample is driven into the bottom of the bore hole by a 140 lbs hammer, falling 30". the number of blows (N) required to drive the cylinder 12" is recorded. |
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What are some common and less common laboratory tests for soil borings?
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Common tests: -strength tests of bearing capacity
-resistance to lateral pressure -slope stabiltiy Less common tests: -compressibility tests -grain size -specific gravity -density |
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What are test pits?
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trenches are dug at the job site that allow visual inspection of the soil strata and direct collection of samples is performed. Typical depth of about 10 ft.
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Soil borings & Test pits:
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-the location of test pits and soil borings are shown on the plot plan and given a number corresponding to the boring log in the soil test report.
-soil tests are requested by the architect but PAID FOR BY THE OWNER. -They are typically shown on the drawings for information only; SOIL TESTS ARE NOT PART OF THE CONTRACT DOCUMENTS. |
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Bearing capacites are generally specified by code:
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-massive crystalline bedrock: 4000 PSF
-sandy gravel or gravel: 2000 PSF -Sand, silty sand, clayey sand, silty gravel and clayey gravel: 1500 PSF -Clay, sandy clay, silty clay and clayey silt: 1000 PSF. -OTHER BEARING CAPACITIES MAY BE USED IF ACCEPTABLE TESTS ARE CONDUCTED AND SHOWN THE HIGHER VALUES ARE APPROPRIATE. |
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Water in soil:
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reduces load-caryig capacity and differential settlement:
-cracking -weakening of structural components -structural failure Foundations below water-table -foundation walls and floor slabs are subjected to hydrostatic pressure -additional load on structure -water proofing is more difficult |
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Solutions to high water table:
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-avoid a basement
-drain tile -gravel and water proofing at the slab -open-web matting against the wall -downspout extensions -slope ground away from the building at the minimum slope of 1/4" per foot. |
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Perched water tables:
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thin layers of impermeable material that hold water above the natural water table.
-when soil dries out differential settlement occurs. |
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What is the soil property of frost?
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-most soils expand and heave when they freeze
-footings must be below the frost line to prevent this heaving. -depth of the frost line varies: specified in local building code. |
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What is the description and solution of expansive soil?
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Description: many clays (Bentonite) expand when wet and shrink when dry.
Solution: -piles or caissons -concrete grade beams |
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What are the two types of foundation systems?
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1. spread footings
2. pile foundations |
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What are wall footings?
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-placed under a continuous foundation wall
-both footing and foundation wall are reinforced. -joint between the footing and the foundation wall is strengthened with a keyed joint. |
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What are the 5 types of spread footings?
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1. wall footings
2. independent column footing 3. combined footings (cantilever footing) 4. strap footings 5. mat or raft foundation |
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What are independent column footings?
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-similar in concept to the wall footing but it supports only on column.
-sizing: divide the total load on the footing by the load -carrying capacity of the soil + a safety factor. |
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What are strap footings (cantilever footings):
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-strap footings use a concrete strap beam to distribute column loads to equalize soil pressure.
-they are used when an exterior columns is next to a property line. |
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What is mat or raft foundation?
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-a continuous foundation is placed under the entire building.
-used when soil has low bearing capacity. -used where the loads are very heavy, such as, high-rise construction. -used where flexibility is extremely important. |
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What are piles?
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-Pile foundations are used when the soil near grade is unsuitable for spread footings.
-piles transmit loads to more secure bearing through: +end bearing +side friction |
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What are the two pile types?
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-driven
-drilled piles (caissons) |
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What are Driven Piles?
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-materials: Steel or timber
-Placed with pile-driving drop hammers, compressed air or diesel engines. |
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What are drilled piles or caissons?
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-formed by drilling out a hole to the required depth and then filling with concrete.
-if the soil is soft a metal lining is used. -belled when soil has low bearing capacity. -when placed under bearing walls the load is transferred with a pile cap or grade beam. |
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Bearing capacities are determined by ...
I. building codes II. the amount of water present in the soil III. unified soil classification system IV. Field tests V. extent and amount of compaction |
I.building codes
II. the amount of water present in the soil IV. field tests |
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What are retaining walls?
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Walls which are used to hold back soil or other materials at a change in elevation.
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What are the forces and modes of retaining wall failures?
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-sliding
-overturning -bending and shear in individual components. |
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What are the types of retaining walls?
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gravity
cantilever wall counterfort wall |
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What is a gravity retaining wall and what are the applications?
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Description- resists forces by its own weight and soil friction. Gets wider as it goes down-resist friction and overturning moment.
applications- low retaining walls (up to 10' in height.) |
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What is a cantilever retaining wall and what is the applications?
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Description: resists forces by its own weight as well as the weight of the soil on the heel of the base slab. it is often constructed with a projecting key at the slab bottom to resist sliding and a toe to resist overturning. (heel reduces overturning and key reduces slide)
Applications: economically limited to about 20' to 25' in height. |
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What is a counterfort retaining wall and what is the applications?
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Description: similar to cantilever wall but with reinforced concrete webs (counterforts) that act as diagonal bracing for the wall. Counterforts and placed at distance equal to or a little larger than one-half the height.(connect wall and heel together to resist overturning moment)
Application: retaining wall higher than 20' to 25'. |
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What are the design considerations for retaining walls?
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-overturning (weight of soil 1.5 times overturning moment)
-sliding-friction (resisting earth pressures) -individual components |
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What are the solutions for built up water in retaining walls?
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-weep holes near the bottom of the wall.
-Gravel next to the back of wall -drain tile in some cases |
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What are single wythe bearing walls?
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Consists of a single unit of unreinforced masonry.
-unsupported height to thickness ratio: solid: 20 to 1 Hollow: 18 to 1 requires horizontal joint reinforcement (typically 9-gage every 16" O.C.) |
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What are reinforced hollow unit masonry bearing walls?
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single wythe of concrete block with vertical reinforcing rods.
unsupported height to thickness ratio: 25 to 1 requires horizontal joint reinforcement bond beams: U-shaped blocks min thickness: 6" for bearing walls |
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What are cavity bearing walls?
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consits of two wythes of masonry, separated by an air space (normally 2' wide)
-unsupported height to length ratio: 18 to 1 Advantages: -extra protection against water penetration -insulation in cavity wythes must be tied together with corrosion resistant tiles: at least 3/16" in Dia. for every 4-1/2 S.F. of wall area. |
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What are reinforced grouted masonry reinforcing walls?
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reinforcing bars installed in cavity wall then filled with grout.
-Unsupported height to thickness ratio: 25 to 1 Application: where additional load-carrying capacity is required or for lateral loads. |
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What are the different types of masonry bearing walls?
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-single wythe
-reinforced hollow unit masonry -cavity -reinforced grouted masonry |
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double wythe-
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extra protection against water penetration
*** dont calculate the air space*** |
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non-bearing retaining walls-
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just carry their own weight (moveable)
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What are the applications for stud walls?
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residential and light commercial
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What are stud walls?
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small members, closely spaced and tied together with interior and exterior sheathing, braced against buckling and to resist lateral loads.
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What are the advantages of stud walls?
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-easy to erect by a small construction crew
-relatively inexpensive -lightweight -materials are readily available -space for insulation and electrical service. |
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what are the different wood stud measurements for bearing walls?
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-studs supporting roof only:
2" X 4" @ 24" O.C. 2" X 6" @ 24" O.C. -Studs supporting one floor and roof: 2" X 4" @ 16" O.C. 2" x 6" @24" O.C. -studs supporting two floors and roof: 2" X 6" @ 16" O.C. -Studs supporting 3 floors and roof: 2" X 8" @ 16" O.C. |
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What are the sheathing for wood studs?
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exterior: plywood, particle board
interior: gypsum board |
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What are the different types of wood studs?
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-baloon framing
- platform framing |
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What are metal studs?
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light-gage C-shaped metal members. Use where high strength is required.
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What are the standard size, gage and spacing of metal studs?
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Standard sizes:
-3-1/2" -3-5/8" -4" -6" Standard gages: -14 -16 -18 Spacing: 24" O.C. |
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What are concrete bearing walls?
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use where high durability and fire resistance is required.
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What is the minimum thickness of multistory concrete bearing walls?
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-6 inches min
-min thickness for basement walls: 8 inches -min thickness for bearing walls 1/25 of unsupported height or length. |
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What is a building envelope and what are the requirements to have one?
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description: wall that encloses the building.
requirements: -structurally sound -accommodate movement -connections allow for on site adjustment -non-bearing. |
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For building envelope exterior cladding must resist:
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-dead loads of the wall system
-horizontal wind loads -seismic laods |
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What are the causes of movement for building envelopes?
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-wind loads
-temperature changes -moisture -earthquakes -differential movement -deflection |
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What are through-building expansion joints for building envelopes?
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put material in wall that can expand and contract with wall.
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WHICH OF THE FOLLOWING AFFECTS THE BEARING CAPACITY OF A MASONRY WALL?
I. WORKMANSHIP. II. THICKNESS. III. NUMBER OF WYTHES. IV. MORTAR TYPE. V. UNSUPPORTED HEIGHT. VI. JOINT REINFORCEMENT. |
I, workmanship
II, thickness IV, mortar type and V. unsupported height |
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What are the controlling factors in beam design?
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-bending
-shear -deflection |
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moment diagrams:
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graphic representation of the moment at all points along the beam
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what is vertical shear in beams?
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the tendency of two adjacent portions of a beam to slide past each other in the direction parallel to the beam.
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What is shear diagrams for beams?
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graphic representation of the values of the vertical shear anywhere along the beam.
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excessive deflection in a beam can cause:
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-finish materials to crack
-pull partitions away from the floor or ceiling -crush full height walls -result in a bouncy floor structure |
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Amount of beam deflection depends on:
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-beam length
-moment of inertia -modulus of elasticity |
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Amount of deflection in beams are limited by building code:
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in many cases the deflection due to live load is limited to 1/360 of the span. total deflection due to live and dead load is limited to 1/240 of the span.
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What are the 5 different beam types?
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1. simply supported beam (statically determinate)
2. overhanging beam (statically determinate) 3. Continuous beam (Statically indeterminate) 4. cantilever beam (statically determinate) 5. fixed-end beam (statically indeterminate) |
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Statically determinate:
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reactions can be found using the equation of equilibrium (summation of horizontal, vertical an moment force = 0 )
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A column must resist:
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-axial compressive forces
-buckling -combined loads |
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The ability of a column to withstand a load is dependent on its:
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-length
-cross-sectional area -moment of inertia -modulus of elasticity |
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radius of gyration:
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the square root of the moment of inertia/area
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Slenderness ratio=
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length of the column/ radius of gyration
gives the max stress a column can resist without buckling. |
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Euler's equation
concentrated load/area= |
(3.141)^2 (modulus of elasticity)/ (slenderness ratio^2)
predicts the actual load just prior to failure. |
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What is a short column?
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compression in the column is typically the controlling factor in sizing.
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What are the controlling factors in beam design?
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-bending
-shear -deflection |
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moment diagrams:
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graphic representation of the moment at all points along the beam
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what is vertical shear in beams?
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the tendency of two adjacent portions of a beam to slide past each other in the direction parallel to the beam.
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What is shear diagrams for beams?
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graphic representation of the values of the vertical shear anywhere along the beam.
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excessive deflection in a beam can cause:
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-finish materials to crack
-pull partitions away from the floor or ceiling -crush full height walls -result in a bouncy floor structure |
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Amount of beam deflection depends on:
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-beam length
-moment of inertia -modulus of elasticity |
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Amount of deflection in beams are limited by building code:
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in many cases the deflection due to live load is limited to 1/360 of the span. total deflection due to live and dead load is limited to 1/240 of the span.
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What are the 5 different beam types?
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1. simply supported beam (statically determinate)
2. overhanging beam (statically determinate) 3. Continuous beam (Statically indeterminate) 4. cantilever beam (statically determinate) 5. fixed-end beam (statically indeterminate) |
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Statically determinate:
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reactions can be found using the equation of equilibrium (summation of horizontal, vertical an moment force = 0 )
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A column must resist:
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-axial compressive forces
-buckling -combined loads |
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The ability of a column to withstand a load is dependent on its:
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-length
-cross-sectional area -moment of inertia -modulus of elasticity |
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radius of gyration:
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the square root of the moment of inertia/area
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Slenderness ratio=
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length of the column/ radius of gyration
gives the max stress a column can resist without buckling. |
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Euler's equation
concentrated load/area= |
(3.141)^2 (modulus of elasticity)/ (slenderness ratio^2)
predicts the actual load just prior to failure. |
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What is a short column?
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compression in the column is typically the controlling factor in sizing.
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what are intermediate columns?
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use of more than one formula maybe required to determine the controlling factor.
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What is the controlling factor in slender columns?
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buckling is the controlling factor in column design, therefore euler's equation would be used.
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What is the load distribution of a bays?
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ex) if you have 4 columns holding up a building one column carries 1/4th of the roof load.
ex) if you have 6 columns the columns in the middle carry half a bay (larger columns than the rest) |
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What are 6 different ways to create lateral stability.
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1. beams
2. rigidly connected 3. diagonal tie rods 4. masonry in-fill 5. diagonal knee brace 6. shear wall |
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What types of buildings use post and beam construction?
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-japanesse houses (19th century)
-modern interiors where one room opens up into another |
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What is the definition of a truss?
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structural systems generally composed of straight members forming a number of triangles with the connections arranges so that the stresses in the members are either direct tension or compression.
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What resembles a warren truss? king post truss?
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-bone structure of a vulture wing resembles a warren truss.
-pelvic region of some birds is similar to a king post truss. |
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What are the 3 components of a truss?
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panels
web members panel points |
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What is the typical depth to span ratio of a flat truss?
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1/10 to 1/20
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Flat Pratt truss can clear span up to...
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70'
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What is the typical depth to span ratio of a pitched truss?
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1/5
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Double Fink or "W" truss can clear spans up to ...
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70'
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What is the economical span range of a truss?
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40 to 200 ft
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What is the typical spacing of trusses?
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10 to 40 ft.
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Spacing of trusses depend on...
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-type of truss
-loads -spanning capability of the purlins |
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What is the load distribution of trusses?
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largest internal forces occur at the upper and lower surfaces.
-additional depth: +little increase of material +increase in spanning capability +load carrying capacity is increased. distribution of forces is usually unequal. |
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What is the load distribution of a trusses
a. top cord b. bottom cord c. web members? |
a. top cord is in compression
b. bottom cord is in tension c. web members generally alternate between tension and compression. |
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What is the load distribution of a top and bottom cord in a cantilevered/double cantilevered truss?
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top cord is in tension and lower cord is in compression
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What are the different trusses classified by shape?
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-parallel cord
-pitched -scissors -bowstring -inverted bowstring -camel back -lenticular |
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What are the different trusses classified by the configuration of web members ?
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-pratt
-howe -king post -belgian -warren |
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What is a flat pratt truss?
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in a flat pratt all web members, except the end ones, slant down in towards the center. the diagonals are in tension and the verticals are in compression, except at the ends.
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What is a pitched pratt truss?
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in a pitched pratt the web members slant away from the center, but the diagonals are in tension and the verticals are in compression.
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What is a pitched Howe truss?
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in a pitched howe the diagonals slant towards the center and are in compression. the verticals are in tension.
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what is a belgian truss?
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diagonal members alternate from tension to compression.
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What is a warren truss?
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formed with equilateral triangles.
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What is a space truss?
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-can carry heavier loads
-keeps it from moving as much in a wind load -formed so they are 3-dimensional. take 2 trusses on side and top and bottom. |
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what is a hinged truss?
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create a pin connection that allows us to rotate so the truss can adjust to the loads. a way to dealing with transportation (can ship in smaller pieces)
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What are the 2 different types of connection trusses?
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wood and steel trusses
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In Levy Ch. 8 what was "the Comet"
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-designed by captain sir Geoffrey de havilland
-one of the first commercial aircrafts driven in WWII -many of them fall "mysteriously" -problem: metal fatigue- the weakening of metals subjected to frequent reversal of stresses from tension to compression. |
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In Levy Ch. 8 what was "Aloha Flight 243"?
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-crashed after it completed 90,000 flights in 20 yrs.
-section of fuse lage was town away and sucked a flight attendant out -safely landed the plane |
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In Levy Ch. 8 what was "comet flight of April 6, 1954"?
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-fuselage ripped open starting at the corner of a window (sensitive to fatigue)
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In Levy Ch. 8 what as "The Point Pleasant Bridge Failure"?
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-Silver Bridge
-on Dec 15, 1967 @ 30 F during rush hour traffic cracks were heard -crashed from Western side -46 ppl died -supported by 2 chains, soft links -the failure of one eye bar in a single link caused the disaster |
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In Levy Ch 15 what was the "Hyatt Regency Hotel"?
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-July 1981 atrium was filled with 1600 ppl
-2 walkways began to fall -114 dead, 200 injured -box beams o the 4th floor walkway was designed to carry the load of one walkway and instead had to carry twice the load -Reasons for failure: 1. the walkways collapsed under loads substantially less than those specified by the Kansas City Building code (KCBC) 2. All the 4th floor box beam-hanger connections were candidate for initiation of walkway collapse 3. The box beam-hanger rod connections, the 4th floor ceiling hanger rods and the 3rd floor walkway hanger rods did not satisfy the design provisions of the KCBC 4. The box beam-hanger to rods connections under the original hanger rod detailed wouldn't have satisfied the KCBC 5. Neither the quality o workmanship nor the materials used played a role in the collapse. |
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In ch 10 of Levy why did the E; Zocalo theatre rise and fall?
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In El zocalo square the theatre in 1940 is 6ft below the surface bc i was built on sand. it pushed the water out of the sand uniformly so nothing happened to the building but it sank. in 1960 it moved back up 6 ft ABOVE the square because skyscrapers had been built around it pushed the water back underneath the theatre.
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In Levy Ch 10 was is a "Flordia Pancake"?
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-used pile to reach solid earth to build a large condominium and hotel complex
-a pile disappeared bc the soil was Florida pancake -weakly supported by loose sand saturated with water. |
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In Levy Ch 10 what is the "leaning tower of pisa"?
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-originally leaned towards the south w/ its top displaced by about 15 ft from the base.
-started leaning to the north during construction -leaned to the south today |
