6 questions

Structural Principles

Which of these is a live load on bridge falsework?

  • a.The weight of the forms
  • b.The weight of the reinforcing steel
  • c.The crew and their tools✓
  • d.The weight of the concrete

Caltrans classes equipment, crew and tools as live load; concrete, reinforcing steel, forms and falsework are dead load.Caltrans Falsework Manual Ch. 3

Structural Principles

A two-span continuous concrete beam is loaded downward. Where is it in tension directly over the middle support?

  • a.At mid-depth only
  • b.At the top✓
  • c.It has no tension there
  • d.At the bottom

Over an interior support of a continuous beam the top is stretched, so top bars are needed there; concrete cracks in tension.FEMA P-749

Structural Principles

A building is open on its street side and has solid walls on the other three. What earthquake behavior is most likely?

  • a.Twisting about its vertical axis✓
  • b.Liquefaction of the foundation soil
  • c.Resonance of the roof only
  • d.Uniform sliding without rotation

Uneven distribution of walls creates a torsional irregularity; the building twists, increasing displacement at the open side.FEMA P-749

Structural Principles

Why are closely spaced ties and hoops detailed in concrete columns?

  • a.To speed concrete placement
  • b.To reduce the columns' weight
  • c.To replace the main bars
  • d.To give the columns ductility✓

Confinement lets concrete members keep carrying load after deforming past peak strength — ductility.FEMA P-749

Structural Principles

Which site is most prone to amplifying earthquake shaking?

  • a.Hard rock near the surface
  • b.Soft soils beside a bay✓
  • c.Bedrock with thin topsoil
  • d.A dense gravel ridge

Soft soils in river valleys and along lakes and bays tend to amplify shaking; hard rock sites experience less intense shaking.FEMA P-749

Structural Principles

A 12-foot-wide slab edge is shored for a single floor with a total dead load of 40,000 pounds. What minimum lateral bracing load applies at that floor?

  • a.4,000 pounds
  • b.1,200 pounds✓
  • c.800 pounds
  • d.400 pounds

Cal/OSHA uses the greater of 100 pounds per lineal foot of floor edge (100 × 12 = 1,200) or 2% of the total dead load (800); 1,200 governs.Cal. Code Regs. tit. 8, 1717

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