Time-history analysis provides for linear or nonlinear evaluation of dynamic structural response under loading which may vary with time. Dynamic equilibrium equations, given by K u(t) + C ^d/_dt u(t) + M d²/_dt u(t) = r(t), are solved using either modal or direct-integration methods. A time function is specified in a load case to characterize loading. Initial conditions may be set by continuing the structural state from the end of a previous analysis. Time-step size, another input parameter, is sensitive to direct-integration methods, and should be decreased until results are not affected. A slightly negative Hilber-Hughes-Taylor alpha value is also advisable to damp out higher frequency modes, and to encourage convergence of nonlinear direct-integration solutions. Material and geometric nonlinearity, including P-delta and large-displacement effects, may be simulated during nonlinear direct-integration time-history analysis. Link objects capture nonlinear behavior during modal (FNA) applications.

See Also

• Multi-support excitation article