Term
| the best shape for a cross section of a single story, axial loaded column is? Why? |
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Definition
| tapered circle, b/c of moment of inertia |
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Term
| Does the strength of the material used in a column effect its buckling load? |
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Definition
| No, buckling is affected by stiffness |
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Term
| List two ways you can vary the capacity of a column in a multistory building without increasing the overall cross-sectional dimension in reinforced concrete & two ways in steel |
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Definition
CONCRETE: rebar & strength of concrete
STEEL: steel grade & thickness of flanges |
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Term
| What three components of a reinforced concrete column can be manipulated to reduce the size of its cross-section? |
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Definition
| aggregate size, rebar/column ties, concrete strength |
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Term
| What are the two methods used to prevent the rebars in a circular concrete column from buckling? |
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Definition
| column ties & spiral ties |
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Term
| What is the difference in function between stirrups and column ties in reinforced concrete members? |
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Definition
stirrups: resisting shear, not equally spaced
column ties: keeps rebar from buckling, evenly spaced |
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Term
| if stirrups are needed in a concrete column, how would they normally be spaced? Why? |
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Definition
| Varied, because there is more shear at connections. |
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Term
| Why are rebars in reinforced concrete columns sometimes spliced? Describe two ways of splicing rebar. |
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Definition
| to create continuous connection through the floor |
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Term
| What determines whether the spacing of the ties in a concrete column is uniform or varied? |
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Definition
| ties= always equally spaced |
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Term
| List 3 ways of putting a column into bending |
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Definition
| Lateral loads, Eccentricity, fixed end moment |
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Term
| What is the advantage of using spaced columns/beams in perimeter locations? |
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Definition
| you eliminate eccentricity |
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Term
| How are bending stress and axial stress related in beam-columns for design purposes? |
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Definition
the more bending stress you put on it, the less axial stress you can have.
Bending Stress + Axial Stress can't exceed allowable stress. |
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Term
| Explain the reasons behind the type of connection between the floor trusses and the columns of the Pompidou Centre in paris |
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Definition
| to eliminate eccentricity |
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Term
| Describe how lateral stability was achieved in the Pompidou Center |
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Definition
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Term
| List 3 potential methods in which lateral stability could have been achieved in Philip Johnson's Glass house |
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Definition
| rigid frame, shear wall, diaphram |
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Term
| What effect (if any) does [increasing or decreasing] the stiffness of the [beam or columns]? |
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Definition
| moment flows toward stiffer material |
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Term
| Will the "thickness of the web members" in a vierendeel truss increase or decreases as they get closer to the supports of the truss? Why? |
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Definition
thickness of web members increase as you get closer to the supports.
because shear increases |
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Term
| List 3 ways of resisting thrust in a single bay rigid frame that will be subjected to uniform gravity loads |
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Definition
| solid foundation, tie rod, dead man |
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Term
| Define sidesway in a frame. What two loading conditions can cause it? |
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Definition
lateral deformation of a frame, due to loading.
- asymmetrical load, & lateral load |
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Term
| How many plastic hinges are needed to create a mechanism of a rigid frame with pinned foundations? WHere are these formed? |
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Definition
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Term
| List 5 causes of compression in the columns of rigid frames |
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Definition
| FEM, gravity, eccentricity, Overturning moment, Lateral loads |
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Term
| List 4 disadvantages of fixed connections |
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Definition
money
thermal expansion/contraction
difficult to do on site
differential settlement. |
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Term
| Are rigid framed structures less susceptible to thermal movements than simple braced structures? |
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Definition
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Term
| How did shape evolve of a Vierendeel truss panel? |
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Definition
| air plane panels prevent shear from being concentrated |
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Term
| Are the panel connections in a Vierendeel struss panel pinned or fixed? What two disadvantages do these trusses have? |
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Definition
FIXED.
- expensive & more material |
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Term
| What is a castellated beam? Explain the advantage of this type of beam when used with a concrete floor slab in composite action: |
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Definition
| less expensive, less material. but you don't need a top flange. |
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Term
| What added efficiency can be gained in composite floor construction by using a castellated beam instead of a rolled section? |
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Definition
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Term
| What is a shear stud and what function does it perform? |
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Definition
| piece of metal welded to top of beam, acts as a shear key with concrete poured on top. |
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Term
| Briefly explain the reason for the failure of the roof in the Kemper Arena in Kansas City. How was it repaired? |
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Definition
concrete attached to steel structure. the anchor rod broke due to thermal expansion & contraction.
repaired - a weaker material for anchors |
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Term
| Why were the windows in the World Trade Center so much narrower than those in the Sears Tower? |
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Definition
| because it was a bundle to tube structure vs. a tube structure. |
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Term
| Why is it advisable to load a truss only at its panel points whenever possible? |
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Definition
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Term
| What 2 effects on a truss of a given span does increasing the number of its panels have? |
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Definition
| decreases length- reduces stress in web, increase amount of material. |
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Term
| Discuss the offsetting cost factors that come into play in choosing either a beam or a truss to span a given distance: |
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Definition
| Truss: less material, much deeper |
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Term
| Waht is the advantage of beam-grid systems versus parallel beam systems? List 2 structural implications of this advantage. |
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Definition
adds torsional rigidity
thicker floor structure, must account for torsional stress |
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Term
| What are the 3 types of stress developed in beam grids? |
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Definition
| torsional, bending, shear |
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Term
| Draw the shape (plan) of a structural bay that is ideal for a 2-way structural system. |
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Definition
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Term
| Which of the beams in a beam grid shown on the board carries the largest load? Why ? |
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Definition
| shorter beams carry more load. Moment flows to greater stiffness |
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Term
| Describe how torsion is developed in beam grids |
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Definition
| beams on top deflects in bending- makes the bottom grid rotate in torsion |
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Term
| Define torsion. Does the modulus of elasticity or the shear modulus of material measure a material's resistance to torsion? |
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Definition
Torsion is rotational shear.
SHEAR MODULUS. |
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Term
| Would a beam grid of WF sections have the same capacity as a beam grid of rectangular sections? Why? |
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Definition
| No, a WF is an open section. It's Iyy is weak, so it can't resist lateral buckling |
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Term
| Is a wide flange section a good section to resist torsion? Would fixing its supports affect its torsional resistance? |
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Definition
| it would help, but it just creates closed sections (more $$) it increases stiffness. |
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Term
| Why are skewed grids more efficient than rectilinear grids in rectangular bays? |
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Definition
| the beams are the same length. |
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Term
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Definition
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Term
| List 3 advantages that space trusses have over parallel trusses. What disadvantages do they have? |
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Definition
advantages:
- torsional stiffness
- not restricted to form
- longer spanning capacity
Disadvantage: - end panel doesn't rest squarely |
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Term
| Is it more efficient to support a truss grid at the top or bottom chord? |
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Definition
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Term
| Must the columns for a space frame be equally spaced? why? |
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Definition
| No. the configurations can vary, can create longer & varying lengths |
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Term
| using one point, two point, and 4 points of supports per column, list 6 ways of supporting a space frame in descending magnitude of allowable loads |
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Definition
1. 4 pt. pyramid support
2. 4 pt. column support
3. 2 pt. column support
4. top chord column
5. bottom chord column
6. linear bottom |
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Term
| What off-the-shelf space frame system best accommodates a radial geometry? |
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Definition
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Term
| What two types of stress are absent in one-way slabs that are present in the other 3 types of flat concrete floors? |
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Definition
1. torsional stress
2. membrane stress |
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Term
| Describe how torsion is developed in two-way slabs |
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Definition
| -develops just beam gris (slab = infinite # of beams) |
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Term
| Describe the method of structurally analyzing a one-way slab: |
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Definition
| treat it like a deep beam |
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Term
| What is the maximum size that an opening can be in a column strip/middle strip zone of a flat plate without the need of an additional drop beam? |
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Definition
Column/column: 1/8
Column/middle: 1/2
middle/middle: 100% |
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Term
| What are the four types of stress developed in flat plate action? |
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Definition
-torsional stress
- membrane stress
- bending
- shear |
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Term
| What advantage is there in using a high strength concrete in the columns of a flat plate system? How can you tell if a higher strength concrete was used in the columns than was used in the plate? |
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Definition
-prevents punching shear,
- concrete will be darker |
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Term
| What is the difference between a two-way slab and a flat slab? |
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Definition
two-way slab: rests on linear supports
one-way slab: rests on point supports |
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Term
| For a given span and loading, would a flat plate or a flat slab require a thicker plane of concrete? why? |
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Definition
| flat plate requires a thicker plane |
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Term
| What two factors contribute to a plate's high reserve of strength? |
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Definition
- post tensioning
- membrane stress |
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Term
| List 4 conceptual approaches in stiffening a plate |
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Definition
- ribs
- post- tensioning
- stronger concrete
- rebar |
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Term
| What is the shallowest floor structure presently in use? |
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Definition
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Term
| in waffle slabs, what can be done to increase the depth of the concrete to accommodate additional steel required in column areas? |
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Definition
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Term
| What can you do in a concrete joist floor system if the shear at the ends of the joists exceeds their capacities, without adding stirrups to the joists? |
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Definition
| thicken width of joist @ connection |
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Term
| Is it a good practice to cantilever a waffle slab? |
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Definition
| No. b/s its a two way system, the beams on the outside wouldn't be supported |
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