ABSTRACT
The introduction of performance-based earthquake-resistant design for buildings and other civil engineering structures has increased the need for simulating realistic ground motions. Combined with recent developments in software tools and structural modeling techniques for time domain transient nonlinear dynamic analysis, the use of simulated time histories of ground motion has gained major importance. Although the use of recorded ground motion under conditions similar to the design earthquake is appealing, there may never be an adequate suite of such data in terms of tectonic structure, earthquake size, local geology, and near-
fault
conditions. The variability of ground acceleration traces induced by the
source
, propagation path, and site characteristics is illustrated in Figure 6.1, where a collection of representative horizontal acceleration time histories is plotted with the same
amplitude
and time scales. A number of methods have been developed and are in use for the adjustment of selected recorded
time histories to provide conformity to site conditions (so-called
accelerogram
scaling) and other
spectrum
matching techniques [e.g., Gasparini and Vanmarcke, 1976; Abrahamson, 1998] that aim to
generate time histories of ground motion whose response spectra match the design response spectrum. Methods that rely on the description of site-or region-specific ground motion time histories in terms of statistically significant parameters, rather than seismological constraints, are also used for the so-called statistical simulation of strong ground motion. For such methods autoregressive moving average (ARMA) processes have been generally used [e.g., Deodatis and Shinozuka, 1988; Ellis and Cakmak, 1991]. These methods do not generally involve rigorous considerations of the physics of the earthquakes and will not be included in the scope of this chapter.
