文档介绍：DYNAMIC ANALYSIS USING
RESPONSE SPECTRUM
SEISMIC LOADING
Prior To The Existence Of Inexpensive puters
The Response Spectrum Method Was The Standard Approach
For Linear Seismic Analysis
INTRODUCTION
The basic mode superposition method, which is restricted to linearly elastic analysis,
produces plete time history response of joint displacements and member
forces. In the past there have been two major disadvantages in the use of this
approach. First, the method produces a large amount of output information that can
require a significant amount putational effort to conduct all possible design
checks as a function of time. Second, the analysis must be repeated for several
different earthquake motions in order to assure that all frequencies are excited, since
a response spectrum for one earthquake in a specified direction is not a smooth
function.
There putational advantages in using the response spectrum method of
seismic analysis for prediction of displacements and member forces in structural
systems. The method involves the calculation of only the maximum values of the
displacements and member forces in each mode using smooth design spectra that are
the average of several earthquake motions.
2 STATIC AND DYNAMIC ANALYSIS
The purpose of this chapter is to summarize the fundamental equations used in the
response spectrum method and to point out the many approximations and limitations
of the method. For, example it cannot be used to approximate the nonlinear
response of plex three-dimensional structural system.
The recent increase in the speed puters has made it practical to run many time
history analyses in a short period of time. In addition, it is now possible to run
design checks as a function of time, which produces superior results, since each
member is not designed for maximum peak values as required by the response
spectrum method.
DEFINITION OF A RESPONSE SPECTRUM
For three dimensional seismic