Steel Structure Design Methods 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 Steel Structure Design Methods flashcards as text
A steel column with KL/r = 80 and Fy = 50 ksi falls into which AISC buckling category?
Answer: Inelastic buckling (KL/r < 4.71√(E/Fy) ≈ 113)
For Fy = 50 ksi, the transition slenderness is 4.71√(E/Fy) = 4.71√(29000/50) ≈ 113; KL/r = 80 is in the inelastic buckling range.
Which effective length factor K applies to a column with both ends pinned (no rotational fixity)?
Answer: K = 1.0
A pin-pin column has no end restraint against rotation, giving K = 1.0 and an effective length equal to the actual length.
What is the purpose of the Cb factor in AISC beam design?
Answer: It accounts for non-uniform moment along the unbraced length, allowing higher capacity
Cb is the lateral-torsional buckling modification factor; moments varying along the unbraced length are less severe than uniform moment, so Cb ≥ 1.0 increases the allowable strength.
In AISC Chapter F, which condition defines a compact section regarding the compression flange?
Answer: λ ≤ λp where λ = bf/2tf ≤ 0.38√(E/Fy)
A compact flange requires bf/(2tf) ≤ 0.38√(E/Fy), allowing the section to reach the plastic moment before local buckling.
For a steel beam experiencing lateral-torsional buckling in the elastic range, nominal moment Mn is proportional to:
Answer: 1/Lb² (inversely proportional to unbraced length squared)
In the elastic LTB range, Mn decreases with 1/Lb via the elastic buckling moment Mcr ∝ (1/Lb)√(EIyGJ + (πE/Lb)²IyCw).
Which AISC design method uses Ω (omega) as the safety factor applied to nominal strength?
Answer: ASD (Allowable Strength Design)
In modern AISC ASD, allowable strength = Rn/Ω, where Ω is the safety factor (e.g., Ω = 1.67 for yielding).
A W14×82 steel column (A = 24.0 in²) with Fy = 50 ksi and φcFcr = 38.2 ksi has a design axial strength of:
Answer: 917 kips
φcPn = φcFcr × A = 38.2 ksi × 24.0 in² = 916.8 ≈ 917 kips.