Comparison of computer codes for seismic analysis of dams

Abstract

An extensive set of computer studies has been made using the EAGD, SAP IV, and ADINA computer codes. Dam-reservoir interaction has been incorporated by two different methods: fluid element and discretized lumped water mass. Parametric studies have been made to investigate the effect of (a) water compressibility vs incompressibility, (b) flexible vs rigid foundation, (c) empty vs full reservoir, and (d) numerical technique on central processor execution time. It has been found that the alpha factor (reservoir absorption coefficient) used in the EAGD program has an influence on the individual modal response of the dam. However, the overall deflections and stresses are not very sensitive to the variation in the value of this alpha parameter. The deflections and stresses obtained from EAGD, which uses finite element simulation for the water reservoir, are compared with SAP IV and ADINA results with discretized lumped water masses. Seismic behavior of the Pine Flat Dam subjected to the Taft earthquake shows that the results of the compressible water model are almost the same as those of the incompressible water model. Lumped added water mass results are about twice as large as results obtained using the fluid element model. A summary of computer execution time is also provided for comparison of relative merits of various numerical techniques. It is noted that EAGD uses a Fast Fourier Transform algorithm whereas SAP IV and ADINA use time domain methods. Execution time for ADINA is three times longer than that for the SAP IV program.