Structural Systems and Design
Load paths and lateral systems
System-level questions test how gravity and lateral loads travel from cladding and floors to diaphragms, collectors, the lateral-force-resisting system, and the foundation. Know shear walls, braced frames, moment frames, dual systems, and diaphragms. Understand torsion and accidental torsion, drift, P-delta, redundancy, overstrength, and seismic detailing. Know code load combinations and the difference between ASD and LRFD. Irregularities such as soft stories, weak stories, and plan offsets must be recognized because they change analysis and detailing requirements.
Traps
Discontinuous load paths are a favorite exam theme. A soft story is a stiffness irregularity; a weak story is a strength irregularity-do not confuse them. Torsion can arise from mass or stiffness irregularity, and accidental torsion is added even for symmetric plans. Strength checks size members, but drift often controls the lateral system. When distributing base shear vertically, verify that story forces sum to the total base shear.
Worked example: Base shear is V = CsW. If W = 1,000 kip and Cs = 0.10, then V = 100 kip. The vertical distribution must sum to 100 kip; applying the entire shear at the roof is a common but incorrect shortcut.
Rule of thumb: Follow the complete load path-cladding to diaphragm to collector to LFRS to foundation-and check drift as well as strength.