Seismic analysis

Seismic performance analysis or seismic analysis is an intellectual tool of earthquake engineering which breaks the complex topic into smaller parts to gain a better understanding of seismic performance of building and non-building structures or their models.
In general, seismic analysis is based on the methods of "structural dynamics". For decades, the most prominent instrument of seismic analysis has been the earthquake "response spectrum method" which, also, contributed to the proposed building code's concept of today.
However, those "response spectra" are good, mostly, for single-degree-of-freedom systems. Numerical "step-by-step integration", applied with the "charts of seismic performance", seems to be a more effective method of analysis for multi-degree-of-freedom structural systems at severe process of earthquake excitation.
The design of structures rests on authorized engineering procedures, principles and criteria meant to design or retrofit structures subject to earthquake exposure. Those criteria are consistent just with the contemporary state of the knowledge about building structures. Therefore, the building design which blindly follows some seismic code regulations does not guarantee safety against collapse or serious damage.
The price of poor seismic analysis may be enormous. Nevertheless, seismic analysis has always been a trial and error process no matter it was based upon physical laws or empirical knowledge.