Cyclic pushover analysis may be performed using either of two approaches, outlined as follows:
Sequence of nonlinear-static load cases
Cyclic pushover analysis may be performed through a sequence of chained pushover analyses. Two key aspects of this approach include:
- Each pushover analysis would be pushing the structure in the direction opposite to that of the preceding pushover load case.
- Each pushover load case, aside from the first, would use stiffness at the end of the previous pushover load case.
Time-history load cases
An alternate approach is to use a single nonlinear time-history load case.
Some special considerations are necessary when using a time-history load case to model applied loading, listed as follows:
- Load should be scaled up or down to achieve the monitored pushover displacement desired for each cycle.
- The time function should consist of linear segments which apply the loads in one direction and then the reverse, possibly with a constant segment to hold loads before their reverse.
- For each cycle in the sequence, the peak positive and negative time-function values must be found, starting with the first cycle of load application.
A sample of a time function is shown in Figure 1:
Figure 1 - Cyclic time function