H-03 — reading output

the software gave you numbers. now read them.

analysis output reader

change the load. read the output.

Adjust the load and watch reactions, shear, moment, and deflection update — the four outputs you check first.

beam geometry
span24 ft
loading
type
w (klf)10
stiffness
E (ksi)29000
I (in4)200
—
M_max (kip-ft)
V = — k   Δ = — in
RL = — k   RR = — k
shear & moment diagrams
deflected shape
live equation
set values above to see the live calculation
V = Internal vertical force plotted along the beam
M = Internal moment plotted along the beam
Δ = Vertical displacement along the beam
R = Support force
explained
Analysis output gives you four things to check first: reactions (do they match hand calculations?), shear diagram (does it jump at the right places?), moment diagram (is the peak where you expect?), and deflection (is it within code limits?). If any of these look wrong, the model has an error.
key concepts
reactionsReactions are the forces the supports push back with to keep the beam in equilibrium

For a simple beam, vertical equilibrium (ΣFy = 0) and moment equilibrium (ΣM = 0) give two equations, two unknowns. Uniform load: R = wL/2. Point load at midspan: R = P/2. Off-center point load: R_L = Pb/L, R_R = Pa/L.

shear diagramThe shear diagram shows internal vertical force along the span

Shear jumps at point loads and reactions, and changes linearly under a uniform load. The maximum shear typically occurs at the supports for simple beams. The shear diagram is the derivative of the moment diagram — where V = 0, M is at a peak.

moment diagramMoment measures the internal bending along the beam

For a simple beam under uniform load, the moment diagram is parabolic with M_max = wL²/8 at midspan. Under a point load, it's triangular. M = 0 at simple supports. The moment diagram drives member sizing — the higher the moment, the bigger the beam.

deflectionThe displaced shape shows where the beam moves and by how much

Deflection depends on load, span, and stiffness (EI). For uniform load: Δ = 5wL&sup4;/384EI. Engineers check L/Δ ratios — typical limits are L/240 to L/360 for floor beams. Excessive deflection causes cracking, ponding, or occupant discomfort.