SITE EFFECTS AND SOIL-STRUCTURE INTERACTION IN THE VALLEY OF MEXICO

An engineering approach is proposed for representing both site effects and soil-structure interaction in extended alluvial valleys, by using the one-dimensional model of shear wave propagation corrected empiric ally to account for lateral heterogeneities and generated surface wave s. The peak structural response is expressed by means of spectral cont ours that are a function of the predominant period of the site and the fundamental period of the structure. Variations of the peak spectral ordinates with the prevailing site period can be deduced from these co ntours. A number of events of firm ground, representative of the most dangerous earthquakes expected in Mexico City, are assumed as design e arthquakes. Making use of the resulting spectral contours, the provisi ons for site effects recommended in the Mexican seismic code are evalu ated. Also, considering as control motion the 1985 Michoacan earthquak e recorded at a representative firm site, spectral contours with soil- structure interaction are obtained which allow one to identify the sig nificant interaction effects originating in the Valley of Mexico for m edium-and long-period structures. The influence and relative importanc e of the critical parameters involved are examined within practical ra nges of interest. (C) 1997 Elsevier Science Ltd.