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Which of the following buildings employ bundled structural tubular framing system?
I) World Trade Center, NY
II)Pompidou Center, Paris
III) Sears Tower, Chicago
IV) John Hancock Bldg, Chicago
V) Transamerica Pyramid, San Fran
A) I and III
B) I, II, III, IV
C) I, III, IV
D) I, II, III, IV, and V
 A) I and III  World Trade Center and Sears Tower
 Perimeter walls from a huge hollow tube cantilevering out of the ground to resist wind and seismic forces. Other examples are moment resisting frames.

Which of the following buildings resists wind loads by acting as a huge trussed tube?
A) Lake Point Tower in Chicago
B) Kresge Auditorium at MIT
C) John Hancock Bldg in Chicago
D) Federal Reserve Bank in Minneapolis
 C) John Hancock  has tubular construction with enormous exposed xbraces that truss the building
 designed by SOM

Which of the following building best expressed the structure concept of the "bundled tube"?
A) Sears Tower
B) John Hancock Bldg
C) CBS Bldg
D) Knights of Columbus Bldg
 A) Sears Tower consists of a "bundle" of 9 tubes that terminate at varying heights
 designed by SOM

True or False: Since truss joints are pure pins or hinges, there are no stresses caused by joint restraint
 flanges/chords: increase towards center
 webs: decrease towards center

lateral forces cause what in shear walls?
both shear and bending stresses

spiral column supports
 spiral column supports more axial load than otherwise identical tied
 reinforcing in a spiral column is always circular pattern
 spiral column can support more load

rigid frame
joints are rigid and capable of transferring bending moment between members

workability of concrete tests?
 1) slump
 2) Kelly ball test

Do concrete systems have greater seismic loads than comparable steel systems?
true

in seismic design  ductility of structure is its ability to
absorb earthquake energy

what does a camber is a gluelam achieve?
 avoid appearance of sag
 eliminate ponding of water
 compensate for deflection

for wind and seismic design, components of a building and connects are required to be...
.. required to be designed for forces which are visually greater than those used in the design of the buildings lateral forces resisting system

tiltup walls
often function as a deep beam spanning between footing pads

Hooke's law
up to elastic limit, unit stress is in direct proportion to unit strain

hyperbolic paraboloid
 can be formed by a series of straight lines
 very stiff structure
 economical in use of material
 curved downward in one direction and up in other

concrete floor framing systems
 pan jast floor system, shear stress near the support is often a controlling factor
 reinforced concrete slab 10ft x 25ft in plan is usually assumed to span 10ft direction only
 concrete floor framing system requiring simplest formwork is flat plate floor
 slab band construction requires more beam reinforcement than a conventional beam used for the same span and loading conditions

order of increasing stiffness:
 1) shear (deflect the least)
 2) braced frame
 3) moment  resisting fr (deflect the most)

specs for compacted fill include
 required density
 moisture content
 lift thickness

Beam
 difference of bending moments between 2 sections of a beam is equal to the area of the shear diagram between 2 sections
 max. unit shear stress in a beam occurs at the neutral axis

truss
 may have various configurations as long as it is comprised of triangles
 can support only load between panel points
 can resist any horizontal load

stress
internal resistance to an external force

punching shear
 tendency of a column to punch through its supporting footing
 twoway shear
 investigated at a distance d/2 from face of column

compared to a momentresisting frame, a shear wall is...
...stiffer

early Christian basilican churches
timber trussed roof

true of false: a rigid frame is more rigid than a braced frame of comparable dimensions
false

why is composite construction economical?
because of the savings in beam weight

1994 Northridge earthquake
many momentresisting frames had connection failures

what is the wind relationship between wind velocity in mph and wind pressure in psf?
wind pressure varies as the square of the wind velocity

designed based on r_{xx} or r_{yg}?
either, whichever results in lower value

cost related to structure
 additional cost to provide seismic resistance for a building to conform to the IBC regulations for SDC D would vary between 5 to 25% with an average of 15% (because structural cost is about 25% of total construction cost, the addition seismic resistance would be roughly 15% of 25% which amounts to 3.75 of total cost
 providing seismic resistance may add 5 to 20% of the structural cost, which is 25% of total cost, therefore 1.25 to 5% of total construction cost

staggered truss
 usually economical for spans greater than 45ft and hotel and residential occupancies
 story high trussed span the full width of the building are arranged in a staggered pattern: trusses in the oddnumbered column lines are erected in a given story, while those in evennumbered column lines are in the stories above and below
 floor system is supported alternately by the top chord of the next
 efficient framing system for the tall narrow buildings typically used for hotel and residential
 generally NOT economical for buildings of less than 810 stories

typical rule of thumb for rebar
# bars/8= inch diameter

Ritcher scale magnitude
each # is 10x ground motion or movement or 33x energy of lower #
 ex. 4.0 to an 8.0
 4/5/6/7/8
 33x33x33x33
 about 1,000,000 times more energy

stirrups
in reinforced concrete provide web reinforcement where the concrete is overstressed in shear

stub girder system
 steel floor beams sit on top of a stub girder, instead of framing into a girder
 because the beams are clear of the girder, they may be designed for simulate continuity
 the space between floor beams can be used for the mechanical and electrical distribution systems
 short lengths of filler beams are welded to the top of the stub girder to provide a connection between the girder and the slab for composite action
 main advantages: reduced weight of steel, reduced story height, simplified steel erection

wind forces
are real exterior surface applied forces

seismic forces
 are simulated forces resulting from a buildings inertia
 seismic design forces are based on inelastic behavior of the structure

flat slab
 drop panels and column capitals used in flat slab are used to reduce shear stress in the slab near the columns and to provide greater effective depth for negative bending moment
 twoway concrete slab, without the use of beams and girders
 in this system, a portion of the slab at the columns is thickened, which is termed a drop panel
 tops of columns are flared and known as column capitals
 drop panels and column capitals are used to reduce shear stress in the slab near the columns and provide greater effective depth for negative bending

shell structures
 a shell or thin shell is a structure with a curved surface that resists load by compression, shear, or tension in its own plane
 too thin to resist any appreciable bending stresses
 shells are strong in resisting uniform loads but cannot resist any substantial concentrated loads, which tend to induce bending

cable roof structures
 a cable is always under tension
 high strength cable is about four times as strong as structural steel
 the dynamic behavior of cablesupported roofs is more critical than that of conventionally framed roofs
 the largest part of the structural framing cost is in the fittings, connections, and anchorage members
 drapped cable will assume the shape of a parabola

heighttowidth ratio
short, squat building=low heighttowidth, less likely to overturn than a tall building
tall, slender building=high heighttowidth ratio

strength design method for reinforced concrete
 margin of safety for reinforced concrete is provided by the load factor and strength reduction factor
 load factor is 1.4 for dead load and 1.7 for live load, is based on the possibility that sometime during the life of the structure, the service loads may be exceeded
 the strength reduction factor allows for variation in material strengths and actual construction dimensions, as well as in accuracies and approximation in design calculations
 depending on the type of stress, varies from 0.65 to 0.90

base plate under steel column
 the base plate under steel columns spreads the column load over a large area of the supporting foundation
 the base plate must be thick enough to resist the resulting bending
 anchor bolts transfer horizontal shear to the footing by the shear in the bolts

tied columns
 usually square or rectangular
 longitudinal bars with separate lateral ties
 same as spiral: longitudal bars carry compressive load  ties hold bars in position and prevent buckling out
 usually an even number of bars is used with code requirement at least four for bars with reaction ties
 longitudal bars may be bundles in 2,3, or 4 bars each, must be tied or wired together
 SPC C and higher: hoops are required and spacing is more stringent

spiral columns
 square or round
 longitual bars help carry the compressive load
 spiral braces the longitudal bars against buckling and confines the concrete
 held firmly in place and true to line by vertical spacers
 min. size of spiral reinforcement is 3/8" clear spacing between spirals must be at least 1" and not more than 3"

a building with a long period is associated with...
 ... flexibility, low acceleration, low seismic force
 every building has a natural or fundamental period of vibration, which varies inversely with its stiffness
 the acceleration of a building during an earthquake and the resulting seismic force depend on the building's stiffness: the stiffer the building, the greater the acceleration and seismic force
 overturning moment is not directly related to a building's period

composite design
 a concrete slab is connected to a steel beam with shear connectors that can develop the ultimate capacity of the concrete or the steel, whichever is less
 because the concrete and steel act together than in conventional steel framing, which generally results in a more economical system, however when a small steel beam is used, deflections tend to become greater, and thus more critical in composite design than in conventional steel framing
 conventional steel framing can always be designed to carry the required loads

factor of safety
ratio of the ultimate strength of a material to its working stress (also called allowable stress)

trusses
 number of members to be joined, as well as the complexity of the joints, usually make truss fabrication expensive, but this is oftenÂ offset by the economy of the material
 truss members are usually subject to axial stress only, unless they support loads between panel points
 stress in chord members depends on depth, but stress in web members is a function of their slope

if a member is inadequate in shear, increasing...
... the area (either width or depth) is effective

if a member is adequate in deflection, increasing...
...the moment of inertia (width) is ok, but depth (d) is cubed and is much more effective reducing deflection

if a member is inadequate in bending, increasing...
...the section modulus (width b) is okay, but depth (d) is square and is much more effective in reducing bending

point of inflection (P.O.I)
 point on the moment diagram where M=0
 only happens when a beam has an overhang
 point in a beam or other flexural member where the bending moment changes sign and has a value of zero

moment
tendency of a force to cause rotation about a given point or axis

yield point
unit stress at which a material deforms with no increase in load

point of inflection
point in a beam or other flexural member where the bending moment changes sign and has a value of zero

moment of inertia
sum of the products obtained by multiplying each unit of area by the square of its distance to the neutral axis


hardwoods
 broad leaves
 deciduous (shedding their leaves)

softwoods
 scalelike or needlelike
 conifers (evergreen)
 *most structrual woods

