# Periodic Load Analysis

Periodic load analysis is to calculate the maximum responses of structures that are subjected to periodic loads. The structure responses include the maximum nodal displacements, velocities and accelerations. The periodic loads are generic and the dynamic load factors of each of the harmonic components of the periodic loads at a given frequency are defined by the users through dynamic load factor table.

Periodic load analysis utilizes modal dynamic analysis results (frequencies, mode shapes & modal masses etc), so at least one modal dynamic analysis must exist with results before doing periodic load analysis.

## Modelling implications

Periodic load analysis utilizes modal dynamic analysis results, so the construction of a GSA model for linear time history analysis is the same as that for modal dynamic analysis. See the modelling implications of Modal dynamic analysis for the requirements of building up a model for modal dynamic analysis which also applies to periodic load analysis.

The spatial distribution and magnitude of the periodic loads are defined in the same way as for defining loads for static analysis. Load combinations (e.g. 1.4L1 + 1.6L2) can also be used in periodic load analysis. The dynamic load factors of each of the harmonic components of the periodic loads at a given frequency are defined in the dynamic load factor table.

As periodic load analysis utilizes the results of modal dynamic analysis, at least one modal dynamic analysis task must be analysed before doing periodic load analysis.

## Results

The results of a periodic load analysis include the nodal displacements, velocities and accelerations. In addition, the nodal displacements, velocities and accelerations can also be plotted against frequencies of the periodic loads from chart view output.

## See also:

Analysis Wizard : Periodic Load Analysis