Seismic response and design for structures located on soft clay sites

Results are presented for 3 soft clay sites forming part of a larger response study of 11 soil sites subjected to earthquakes of varying intensity and frequency content. The results are presented in the form of spectral ratios (surface to rock), base shear coefficients, and foundation factors. They indicate that large amplifications can be expected at structural periods close to the site period. Comparisons are made with the National Building Code of Canada (NBCC) 1990 provisions for base shear coefficients and foundation factors. These show that the NBCC provisions are adequate when the excitation is low or medium period in nature. For high-period excitation of low intensity, high amplifications that exceed the code provisions are produced. Key words: seismic, design, clay, soft, site, response, spectra, amplification, base, shear.