Investigation of alternative seismic design procedures for standard buildings.

摘要

The seismic design provisions of most building codes in the United States specify ground motion parameters for various regions of the country and provide simple formulas to determine a distribution of lateral forces for which the structure should be designed. The simple formulas typically involve the use of one or more "factors" to account for anticipated inelastic behavior of the structure, relative importance of the structure, and site soil effects. Although these code provisions are very simple to use, they oversimplify a complex problem and are based on many implicit assumptions which many designers may not appreciate. Furthermore, the reliability of the final design is not known. An alternative design and analysis procedure, in which the underlying assumptions are more clearly defined and which provides a more uniform level of reliability in the final design, is presented. The procedure requires the designer to consider two levels of earthquake excitation. "Equivalent" single-degree-of-freedom models and uniform hazard response spectra are used to evaluate structural performance. Deterministic design-checking equations are derived based on displacement-based performance criteria which are expressed in probabilistic terms. The deterministic design equations account for the uncertainty in predicting site soil effects, the uncertainty in seismic hazard, and the approximate nature of the simplified models of the structure through the use of design factors. The goal of the alternative procedure is to enable designers to achieve code-specified target performance objectives for moderate and severe levels of earthquake excitation.