Performance Based Seismic Design (PBSD)

Historically, buildings have been designed and constructed in conformance with building codes whose primary goal has been to minimize the potential for loss of life in a major earthquake. Over the years, the codes have become more detailed in their prescriptive requirements and expanded to address minimum requirements for the anchorage of non-structural building components. Despite these continual improvements and expansions in scope, the primary assumption of the building codes is that buildings will be damaged by severe earthquakes, and through damage to structural assemblages, energy from the earthquake will be sufficiently dissipated to prevent building collapse.

Following the 1989 Loma Prieta and 1994 Northridge earthquakes, building owners, managers and design professionals realized that buildings designed to the minimum code standards of life safety protection could suffer extensive and costly damage in response to moderate earthquake induced ground shaking. In some instances, operations could be suspended for months while repairs are affected. Other damages, such as loss of inventory could produce crippling consequences.

In response to these concerns, structural engineers have initiated the development of a concept of seismic design called Performance Based Seismic Design (PBSD). Philosophically, this design aproach permits a building owner/operator to select an acceptable level of building damage for a given intensity of earthquake ground shaking which can then serve as an objective or target for the seismic design effort. Buildings continue to be designed for the minimum levels of life safety protection offered by the code based design approach, but PBSD offers owners/operators the opportunity to limit business interruption economic loss and other consequences for less severe but more probable earthquake hazards.

PBSD criteria can be developed and implemented for any building type located in any seismically active region of the world. Working with a qualified team of design professionals, appropriate intensities of ground shaking can be developed using probabalistic or deterministic methodologies and an acceptable level of building damage can be established for both structural and non-structural components. By targeting a level of acceptable performance for moderate earthquake events, owners/operators of critical facilities or economically vulnerable operations can dramatically improve their ability to maintain functions in an economical and rational fashion.