ABSTRACT
Seismic computations of long-span structures have long been an issue of great concern. Such
computations are usually executed numerically using schemes in the time domain (i.e., time history). For
short-span bridges, all supports can be assumed to move uniformly and the response-spectrum method
(RSM) is a suitable computation tool. For long-span bridges, however, various spatial effects such as the
wave-passage effect, the incoherence effect, the local site effect, and so on, may be important. Such spatial
effects cannot be dealt with directly by the conventional RSM. Instead, the time-history method (THM)
is the most widely used method for these systems. The time-history scheme requires solving the dynamic
equations for a number of seismic acceleration samples. The results are then processed statistically to
produce the quantities required by the designs. This process is rather complex and requires a considerable
computational effort. As a result, more efficient and effective methods are under investigation.
