Description |
Simulation of Earthquake Ground Motions. SIMQKE-II generates an array of differing but spatially correlated earthquake ground motions at an arbitrary set of points, optionally statistically compatible with known or prescribed motions at other locations. The simulated motions can be used for more realistic earthquake resistant design of extended structures such as bridges, power plants, dams, shopping malls, etc., where the input motion during an earthquake event is not expected to be identical at all points in contact with the ground. It can also be used for the post-analysis of earthquake damaged structures given recorded motions in the vicinity. Supplied with a target ground motion spectral density function, which may be evolutionary in nature, the program employs Covariance Matrix Decomposition in the frequency domain followed by Best Linear Unbiased Estimation and an inverse Fast Fourier Transform to produce the nonstationary, spatially correlated, conditioned or unconditioned ground motions. The evolutionary nature of the motion is modeled by subdividing the motion into a sequence of time windows, within each of which a target spectral density function is specified. An averaging algorithm is applied to smoothly connect the sequential windows. The spatial correlation is based on the phase aligned motions and is specified through simple parameters supplied to one of a number of typical space-frequency correlation functions. It can be used in combination with the original SIMQKE, which has a number of preprocessing options related to prescribed response spectra. In particular, SIMQKE may be used to generate, based on user-specified response spectra, the corresponding input spectral density functions for SIMQKE-II. |