A nonlinear static structural analysis technique that incrementally applies a predefined lateral load pattern to a structural model to trace its capacity curve (base shear versus displacement), identify formation and sequence of plastic mechanisms (hinges), and estimate inelastic displacement capacity and likely collapse mechanism without performing full nonlinear time-history dynamic simulation.

Principle

By imposing increasing static lateral demand shapes, a structure's monotonic strength and deformation capacity and the development sequence of plastic mechanisms can be identified; when the first-mode dominates, this static pushover captures the progression to inelastic limit states and provides a capacity curve usable for approximate performance assessment.

Demonstration

Illustrative scenario: A three‑story moment‑frame model is subjected to a lateral load pattern proportional to the first-mode shape and incrementally scaled. At each increment the solver records base shear and roof displacement; plastic hinges form first at the base columns then at beam ends. The capacity curve shows the target displacement where the structure exceeds acceptable drift and forms a collapse mechanism.

Misapplication

Relying on a single lateral load pattern for irregular, highly asymmetric, or higher-mode-sensitive structures, using pushover results to predict time-history peak responses or dynamic amplification, or interpreting hinge rotation thresholds as absolute collapse without validating with dynamic analysis.

Consequence

Provides an efficient, computationally inexpensive way to estimate capacity, probable failure sequence, and performance levels for many buildings, useful in design and retrofit screening; however it may misestimate demand for structures where dynamic higher-mode effects or soil–structure interaction are significant.

Reversal

Unreliable when higher-mode participation, strong torsion, weak-story mechanisms, rate-dependent materials, or near-source pulse-like ground motions govern response; in those cases nonlinear time-history analyses (e.g., IDA) or more advanced procedures are required.

Boundary

Clearly within: regular, medium-rise buildings with dominant first-mode response and reasonably uniform mass/stiffness distribution. Boundary case: buildings with moderate plan irregularity or mass eccentricity where multiple load patterns should be checked. Clearly outside: tall slender structures, highly irregular plans, strong soil–structure interaction, or systems with important higher-mode dynamic effects.

Semantic Tension

Computational expediency and clear mechanism insight versus the need for dynamic fidelity to capture higher-mode and time-dependent phenomena.

Synthesis

Pushover analysis reveals probable inelastic mechanisms and generates a capacity curve for rapid performance assessment; it is a powerful screening and design tool when first-mode behavior dominates but must be augmented by dynamic analyses for cases where higher-mode or rate effects control seismic demand.