When the model is nonlinear the only option for dynamic analysis is a time-history analysis which steps through the solution one time step at a time. There are two basic schemes for this time stepping: implicit and explicit. The time-history option implemented in GSA is explicit.
Footfall induced vibration analysis is to evaluate the responses of structures subjected to the actions of human footfalls. The structural responses include nodal accelerations, velocities and response factors etc. The human footfall loads are considered as periodical loads which are represented by a number of harmonic loads according to Fourier series theory. The detailed descriptions of human footfall loads can be found from references 35, 29 and 1 in the Bibliography which are also listed below. Footfall induced vibration analysis utilizes dynamic analysis results (frequencies, mode shapes & modal masses etc) to calculate the structure responses . The outputs of footfall analysis are the maximum responses of the structure for the given ranges of walking frequencies etc. The following three design guides of footfall analysis can be considered:
Tables of output may be formatted by displaying the output in a standard Output view or a Grid output view. Outputs for inspection, presentation or printing are best formatted with a standard Output view, while the Grid output view facilitates the copying of output to spreadsheets.
GSA can calculate a large range of results. However not all these results may be required so this allows for selection of particular results to be stored. For an explicit solver these can be selected separately for Full Model Results and for Selected Model Results
Measures of the utilisation of the member’s capacity. Remember that their values will not be directly comparable from design code to design code, and that the calculation of some of them is highly nonlinear. If any of them is greater than 1, then the member has failed.