Tectonic hazards/Seismic performance

Seismic performance is an execution of a structure's ability to sustain its due functions, such as safety and serviceability, at and after a particular earthquake exposure. A structure is, normally, considered safe if it does not endanger the lives and wellbeing of those in or around it by partially or completely collapsing. A structure may be considered serviceable if it is able to fulfill its operational functions for which it was designed.

Basic concepts of the earthquake engineering, implemented in the major building codes, assume that a building should survive The Big One (the most powerful anticipated earthquake) though with partial destruction. Drawing an analogy with a human body, it will have dislocated joints, fractured ribs, traumatized spine and knocked out teeth but be alive and, therefore, quite O.K. according to the prescriptive building codes. This situation is a major barrier to implementation of any structural innovations in the earthquake engineering technologies employing the seismic vibration control and, particularly, the most effective brands of base isolation.

However, alternative performance-based design approaches already exist and are implemented at earthquake engineering research. Some of them, for assessment or comparison of the anticipated seismic performance or for seismic performance analysis, use the Story Performance Rating R as a major criterion while the Seismic Performance Ratio (SPR) is used for a rather accurate prediction of seismic performance of a building up to the point of its state of severe damage.

Anyway, replacement of the present prescriptive design standards with the future codes of performance is not an easy task: most of the designers would be reluctant to accept any additional legal obligations.