When the Nonlinear / Use Load Histories check box on the analysis dialog box is selected you can specify a time dependence function for each load and constraint set. The default time dependence function is a predefined linear ramp function from (0,0) to (1,1). It provides a magnification that increases linearly from 0 to reach a value of 1 at time equal to 1. You cannot delete the ramp function with the Delete button on the Functions dialog box.