Structural: Statics, Load Combinations, and Member Checks
Analysis first
Structural questions usually reduce to statics, load combinations, and member behavior. Draw the free-body diagram, solve reactions, then construct shear and moment diagrams. For a simply supported beam with uniform load w over span L, maximum moment is wL²/8 at midspan and maximum shear is wL/2 at the supports. A frequent trap is using the wrong span, forgetting self-weight, or mixing service loads with factored loads.
Design codes and limits
Know the difference between ASD and LRFD. A typical strength combination is 1.2D + 1.6L; service combinations are used for deflection and vibration. For steel, check yielding, rupture, buckling, and connection limit states. For reinforced concrete, verify tension-controlled behavior, minimum reinforcement, development length, and shear capacity. Column questions hinge on effective length K and slenderness; a pinned-pinned column has K = 1.0, fixed-free K = 2.0.
Worked example
A 20 ft simply supported beam carries w = 2.0 klf, including self-weight. Maximum moment = wL²/8 = 2.0(20²)/8 = 100 kip-ft. Maximum shear = wL/2 = 2.0(20)/2 = 20 kips. If the question asks for factored moment under 1.2D + 1.6L and the 2.0 klf is all dead load, Mu = 1.2(100) = 120 kip-ft. The trap is applying both factors to a load that is entirely one type.
Detailing and load paths
Understand tributary area, one-way versus two-way action, diaphragm and collector behavior, and connection eccentricity. Wind and seismic questions often turn on load path continuity and whether a component is part of the lateral-force-resisting system. Check units: kip-ft versus kip-in.