Structural Lateral Depth PE

Always check AASHTO tables for correct Cd values - they vary significantly by superstructure type. Truss bridges have the highest drag coefficient (2.0), while box girders are lowest (1.2). Velocity pressure q is typically given or calculated from wind speed using q = 0.00256V².

Key exam points: Always determine α_c from height-to-length ratio first. For ratios between 1.5 and 2.0, use linear interpolation. Remember that A_cv is the gross cross-sectional area of the wall parallel to the applied shear. Don't confuse with net area or effective area.

This equation is only valid for T < TS (short period range). For longer periods, different equations apply. Always verify you're in the correct period range before applying. Common on lateral forces and seismic design problems.

P-Delta effects become critical when θ approaches 0.1. Values above 0.25 indicate potential instability. Always check if lateral drift moments need amplification - this is required by most codes for drift-sensitive structures.

Remember that C_s has upper and lower limits per ASCE 7. Always check against minimum C_s = 0.044×S_DS×I_e ≥ 0.01. For long-period structures, the upper limit involves S_D1/(T×R/I_e). Most exam problems give C_s directly or provide enough data to calculate it first.