Civil Engineering PE Reinforced Concrete Design 5

Question 1

A pretensioned concrete beam uses ½-in diameter strands with fpu = 270 ksi. The ACI 318 approximate prestress loss for an interior exposure condition (total losses) is typically assumed to be:

Accepted Answer

20%

Answer

10%

Answer

15%

Answer

25%

Question 2

The maximum spacing of shear reinforcement in a reinforced concrete beam (where Vs < 4√f'c × bw×d) per ACI 318 is:

Accepted Answer

d/2

Answer

d/4

Answer

d

Answer

24 in

Question 3

Cracking moment Mcr for a rectangular beam section (b = 12 in, h = 24 in, f'c = 4000 psi) is most closely:

Accepted Answer

56 ft-kips

Answer

42 ft-kips

Answer

68 ft-kips

Answer

80 ft-kips

Question 4

The long-term deflection multiplier λΔ for a simply supported beam with no compression reinforcement (ρ' = 0) after 5 years is:

Accepted Answer

2.0

Answer

1.0

Answer

1.4

Answer

2.4

Question 5

Which ACI 318 provision governs the maximum reinforcement ratio for a tension-controlled singly reinforced beam?

Accepted Answer

Net tensile strain εt ≥ 0.004

Answer

ρmax = 0.75ρb

Answer

Net tensile strain εt ≥ 0.005

Answer

As,max = 0.04bwd

Question 6

A corbel projecting from a column must be designed for which primary force combination?

Accepted Answer

Vertical shear plus horizontal tensile force

Answer

Vertical shear only

Answer

Bending moment and axial compression

Answer

Torsion and shear

Question 7

The strut-and-tie method (STM) per ACI 318 Appendix A is most appropriate for designing which type of region?

Accepted Answer

Discontinuity (D) regions near concentrated loads or geometric changes

Answer

Slender beams with L/d > 5

Answer

Uniformly loaded one-way slabs

Answer

Columns with low eccentricity