Please describe in detail the analysis you need to do. Describe in detail the "Triangular shocks" load.
It is possible to apply a series of triangular profiles of acceleration vs time in a full Transient Structural model and obtain the transient response of the structure and use any nonlinear behavior you want such as contact, large deflection and hyperelastic material. No Modal analysis is required.
If you have a linear system, you can use a Modal analysis and feed the modal results into the setup cell of a Transient Structural model to get a transient response in much less time than the full Transient Structural with no Modal.
A train of triangular shocks is not a random vibration.