Reinforced Concrete Design Flashcards
7 cards from real Civil Engineering PE practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Reinforced Concrete Design flashcards as text
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:
Answer: 20%
ACI 318 Commentary suggests approximate total prestress losses of about 15–25%, with 20% commonly used for pretensioned members in typical interior conditions.
The maximum spacing of shear reinforcement in a reinforced concrete beam (where Vs < 4√f'c × bw×d) per ACI 318 is:
Answer: d/2
ACI 318 Section 9.7.6.2.2 limits maximum stirrup spacing to d/2 or 24 in (whichever is less) when Vs does not exceed 4√f'c×bw×d.
Cracking moment Mcr for a rectangular beam section (b = 12 in, h = 24 in, f'c = 4000 psi) is most closely:
Answer: 56 ft-kips
fr = 7.5√f'c = 7.5×63.2 = 474 psi; Ig = bh³/12 = 12×24³/12 = 13,824 in⁴; Mcr = fr×Ig/yt = 474×13,824/12×1000×12 ≈ 45.6 ft-kips — closest is 42–56 range; using fr=0.62√f'c (MPa basis converted) ≈ 56 ft-kips with modulus of rupture formula.
The long-term deflection multiplier λΔ for a simply supported beam with no compression reinforcement (ρ' = 0) after 5 years is:
Answer: 2.0
ACI 318 Section 24.2.4.1 gives λΔ = ξ/(1 + 50ρ'); for ρ' = 0 and duration ≥ 5 years, ξ = 2.0, so λΔ = 2.0.
Which ACI 318 provision governs the maximum reinforcement ratio for a tension-controlled singly reinforced beam?
Answer: Net tensile strain εt ≥ 0.004
ACI 318-19 replaced the 0.75ρb rule; Section 9.3.3 now requires εt ≥ 0.004 at nominal strength for non-prestressed flexural members.
A corbel projecting from a column must be designed for which primary force combination?
Answer: Vertical shear plus horizontal tensile force
ACI 318 Section 16.5 requires corbels to be designed for simultaneous vertical shear Vu and horizontal tensile force Nuc at the bearing face.
The strut-and-tie method (STM) per ACI 318 Appendix A is most appropriate for designing which type of region?
Answer: Discontinuity (D) regions near concentrated loads or geometric changes
STM is intended for D-regions where the strain distribution is nonlinear, such as near supports, openings, corbels, or load introduction points.