Effect of multi support excitation on seismic response of embankment dams

Spatial Variation of Earthquake Ground Motion (SVEGM) is clearly indicated in data recorded at dense seismographic arrays The main purpose of this paper is to study the influence of SVEGM on the seismic response of large embankment dams. To this end, the Masjed Soleyman embankment dam, constructed in Iran is selected as a numerical example. The spatially varying ground motion time histories are generated using spectral representation method. According to this methodology, the generated time histories are compatible with prescribed response spectra and reflect the wave passage and loss of coherence effects. To investigate the sensitivity of the dam responses to the degree of incoherency, three different coherency models are used to simulate spatially variable seismic ground motions. Finally, the seismic response of the dam under multi-support excitation is analyzed and compared to that due to uniform ground motion. Also, the Newmark's method is used to estimate seismic-induced permanent displacements of the embankment dam. The analysis results reveal that the dam responses can be sensitive to the assumed spatial variation of ground motion along its base. As a general trend, it is concluded that the use of multi-support excitation, which is more realistic assumption, results in lower acceleration and displacement responses than those due to uniform excitation.