Diagrams, Axial, Shear, and Flexure
Force-effect questions test shear and moment diagrams, axial tension and compression, shear, flexure, and equilibrium setup.
How to study for PE Civil: Structural
Use the NCEES specification as your map: build load-path, analysis, materials, detailing, connection, foundation, and temporary-works fluency while practicing standard-specific judgment.
Core concepts
Concept 1
Equilibrium establishes reactions and internal axial, shear, and moment actions for a correctly isolated free body.
Exam cue: Choose a free body that exposes no more unknowns than the available equilibrium equations.
Concept 2
Load, shear, and moment diagrams are linked by derivatives, integrals, and concentrated-force discontinuities.
Exam cue: Check diagram slope and jumps against the applied distributed loads, point forces, and couples.
Concept 3
Stress calculations require the appropriate gross, net, bearing, shear, or section property with consistent units.
Exam cue: Convert kip-ft to kip-in before dividing by section properties in inches.
Risk pitfalls and guardrails
Confusing a support reaction with total load or assigning the wrong sign to an overhang reaction.
Guardrail: Do not stop at one capacity number: verify strength, serviceability, stability, detailing, construction stage, and every connection to the foundation.
Using average shear where the maximum elastic distribution is required.
Guardrail: Do not stop at one capacity number: verify strength, serviceability, stability, detailing, construction stage, and every connection to the foundation.
Moving a load in an influence-line problem without preserving axle spacing or the response being maximized.
Guardrail: Do not stop at one capacity number: verify strength, serviceability, stability, detailing, construction stage, and every connection to the foundation.
Memory anchors
Shear Diagram
A shear diagram shows internal shear variation along a member.
Moment Diagram
A moment diagram shows internal bending moment variation along a member.
Axial Force
Axial force acts along a member axis in tension or compression.
Shear Force
Shear force acts transverse to the member axis and can govern webs, connections, or interfaces.
Flexure
Flexure creates bending stress and curvature from moment demand.
Equilibrium
Equilibrium requires forces and moments to balance for the chosen free body.
Influence Line
Influence lines help place moving loads for maximum response.
Sign Convention
A consistent sign convention prevents reversed shear, moment, or axial conclusions.
Point-Load Jump
A concentrated transverse force creates a jump in the shear diagram equal to the force magnitude.
Applied Couple
A concentrated couple creates a jump in the moment diagram without a matching shear jump.
Moment Slope
The slope of the bending-moment diagram equals shear under a consistent sign convention.
Zero-Force Member
Joint geometry and loading can identify a truss member that carries zero force for a specific load case.
Shear Flow
Shear flow q = VQ/I is force per unit length transferred along a built-up-member interface.
Section Modulus
Elastic flexural stress equals moment divided by section modulus when units are consistent.
Checkpoint rule
Do the check-up only after you can summarize each concept in one sentence and identify one dangerous pitfall from memory.
Knowledge Check (after reading)
Short check-up to confirm understanding of this module.
Check-up Questions
A simply supported 24 ft beam carries a uniform load of 2.0 klf over the full span. What reaction acts at each support?
For the same simply supported 24 ft beam with 2.0 klf uniform load, what is the maximum bending moment?
Answer all questions to submit.
Next step personalized recommendations
Continue learning
Move forward only after this module is stable.
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