Analysis, Verification & Post-Processing

For a linear-elastic static model, STAAD assembles the global stiffness system, applies boundary conditions and loads, solves nodal displacements, and recovers member/element actions and support reactions. Linearity means stiffness is treated as independent of the load level and the principle of superposition can be used where the analysis formulation permits it.

If second-order geometry, tension/compression-only behavior, cables, material yielding, contact, staged effects, dynamic inertia, or other nonlinear/time-dependent behavior materially affects the engineering decision, select and verify an analysis formulation that represents that behavior. Do not infer advanced behavior from a linear run.

A suspicious reaction total can indicate omitted loads, wrong directions, unsupported/disconnected components, load-generation boundaries that do not cover the intended area, or misunderstanding of which loads are included in the displayed case. Small numerical residuals are different from a structural-scale imbalance; interpret tolerance in context.

Before comparing drift or deflection to limits, inspect whether the structure moves in the expected direction. Unexpected rigid-body motion, one joint moving far more than neighboring joints, a beam separating visually from a column, or a twisting response in a nominally symmetric frame can expose modeling errors immediately.

Graphical deflected shapes are typically exaggerated for visibility. Read the actual displacement values and units; do not infer physical displacement magnitude from the screen scale alone.

Member results are reported in the member-local system. Always show/understand local axes before interpreting signs. A positive/negative moment diagram is only meaningful when the member direction and software sign convention are known.

For a simply supported beam of span $L$:

• centered point load $P$: $M_{max}=PL/4$, $|V|_{max}=P/2$
• full-span uniform load $w$: $M_{max}=wL^2/8$, $|V|_{max}=wL/2$

These idealized relationships are valuable regression checks for educational simulations and small benchmark models before trusting a large model.

Whenever reporting a maximum displacement, reaction, moment, utilization or reinforcement demand, also record which load case/combination and location produced it. Separate serviceability envelopes from strength/design envelopes so a service deflection is not accidentally checked using a strength combination—or vice versa.

Plate moments/stresses are expressed relative to element local axes. Before translating plate output into engineering reinforcement directions or membrane actions, confirm the local axes, element orientation, and whether adjacent elements use a consistent orientation.

Finite-element stress/moment peaks near supports, point loads, openings, re-entrant corners, rigid links or abrupt stiffness changes can be mesh-sensitive or singular. Review distributions, equilibrium, design strips/cut lines/averaging methods appropriate to the engineering workflow, and mesh-refinement sensitivity rather than treating one extreme pixel as a directly constructible demand.