Structural Engineering
Structural engineering analyzes and designs members that carry loads safely to the ground: beams, columns, frames, and foundations. The PE Civil exam tests statics of structures, member behavior, and the design codes (ASCE 7, AISC, ACI) used in practice.
Beam Reactions and Moments
A simply supported beam under symmetric loading splits the load equally: each reaction is w·L/2 for a uniform load. The maximum bending moment is w·L^2/8 for a uniform load and P·L/4 for a central point load. These closed-form results anchor most beam checks.
Section Properties
Bending resistance depends on cross-section geometry. The moment of inertia of a rectangle is b·h^3/12 and its section modulus is b·h^2/6. Because depth is cubed in the moment of inertia, deeper sections are far stiffer, which is why beams are oriented with their long dimension vertical.
Loads and Design Codes
LRFD design factors loads by their uncertainty; the basic gravity combination is 1.2D + 1.6L from ASCE 7. Steel design uses AISC (A36 steel yields at 36 ksi, A992 at 50 ksi); concrete uses ACI with Grade 60 rebar. Bending stress is M/S, kept below the code-allowable value.