Civil Engineering PE Steel Structure Design Methods 2

Question 1

In LRFD design, which load combination governs for a steel beam subjected to dead load D = 20 kips and live load L = 40 kips?

Accepted Answer

1.2D + 1.6L = 88 kips

Answer

AISC LRFD load combination 1.2D + 1.6L = 1.2(20) + 1.6(40) = 88 kips governs over 1.4D = 28 kips.

Question 2

What does the resistance factor φ = 0.90 represent in LRFD steel design for tension yielding?

Accepted Answer

A safety margin accounting for variability in material strength and fabrication

Answer

φ = 0.90 for tension yielding represents the probability-based reduction accounting for material and fabrication variability to ensure adequate reliability.

Question 3

A W-shape beam has a plastic section modulus Zx = 120 in³ and Fy = 50 ksi. What is the plastic moment Mp?

Accepted Answer

6,000 kip-in

Answer

Mp = Fy × Zx = 50 ksi × 120 in³ = 6,000 kip-in.

Question 4

In ASD for steel, the allowable bending stress Fb for a compact section in a braced frame with Fy = 36 ksi is typically:

Accepted Answer

0.66Fy = 23.76 ksi

Answer

ASD allowable bending stress for compact laterally braced beams is Fb = 0.66Fy per AISC 9th edition.

Question 5

Which steel design method explicitly accounts for the probability of failure through reliability index β?

Accepted Answer

LRFD

Answer

LRFD was calibrated using reliability theory to achieve a target reliability index β ≈ 3.0 for typical members.

Civil Engineering PE Practice Test

Civil Engineering PE Practice Test

Civil Engineering PE Steel Structure Design Methods 2