In practice, seismic design checks are usually carried out using the response spectrum method, as it has many advantages: The application is relatively straightforward, the calculation is quite quick, and the results are easy to understand. The method is based on spectra in the form of specific diagrams. They express how the model "responds" to a vibration excitation in its supports. This way, it is possible to draw conclusions about the response of the supporting structure in the event of an earthquake.
The response spectra are derived from the records of numerous earthquakes that have occurred around the world. They are also regulated in the corresponding standards, such as EN 1998‑1 [1] or ASCE 7 [2]. For a detailed explanation of the response spectrum method, see Meskouris [3] and Wilson [4], for example.
The Response Spectrum Analysis add-on is an extension of Modal Analysis. It allows you to carry out a seismic analysis according to the multi-modal response spectrum method. The spectra can be selected in compliance with the standards, or user-defined. The resulting forces and deformations are then calculated based on these specifications.
The currently available design standards and a summary of the functional scope can be found in the respective product description of the Response Spectrum Analysis add-on for RFEM 6 / RSTAB 9.
