CSiPlnat offers linear and nonlinear time history dynamic analysis using using either modal or direct-integration methods with no practical limit on the number of time history cases or the size of the time history functions. Time history cases can be load sequenced from the end state of a nonlinear time history case or from the end state of a nonlinear static case.
Modal time history cases typically run faster than direct integration load cases and they are not as sensitive to time step size. Although nonlinear modal time history cases can account for nonlinear boundary conditions (gaps, friction, 1-way supports, etc.), nonlinear modal cases cannot account for nonlinear P-delta effects. Modal time history cases can only be load sequenced after another nonlinear modal time history case.
Direct integration time history cases are sensitive to time-step size, which should be decreased until results are not affected. Nonlinear direct integration time history cases can be load sequenced after either a nonlinear time history dynamic analysis case or a nonlinear static analysis case, and can account for nonlinear boundary conditions and nonlinear P-delta effects.
Time history analysis may be initiated using the process which follows:
- Create the model and assign support conditions.
- Select Define > Functions > Time History to define a time-history function which characterizes load variation over time.
- Assign load conditions to the model.
- Define either a modal or direct-integration time-history load case through Define > Load Cases.
- Enter on the Load Case Data form under Loads Applied, the following fields:
- Load Type. Select load pattern or specify an acceleration.
- Load Name. Either load pattern name or acceleration direction
- Function. Select the time history function which characterizes load variation in time.
- Scale Factor If acceleration load type apply scale factor as a percentage of G in current unit
6. On the left side of the time history load case dialogue under Properties, users will find options to specify load sequencing using the 'Continue from End state of' field, an option to select a mass source, and option to specify P- delta if it's a nonlinear direct integration time history case.