Effect of Built Environment on Free-Field Motion for Very Soft, Urbanized Sites

A preliminary numerical investigation is presented on the long distance effects of soil-structure interaction for important buildings located on soft soils. A simple 20 model is considered, with homogeneous rectangular buildings resting on a single, horizontal, soft layer overlying a much stiffer half-space, impinged by SH waves. Computations are made for different parameter sets, in order to analyze the respective effects of the main parameters: clay layer thickness and frequency, building size, and spacing between buildings. For realistic building properties, wave diffraction related with soil- structure interaction is shown to alter the free-field surface motion up to distances of at least 1 km from the next building: duration as well as amplitude are significantly increased at some frequencies, while they may be reduced at other frequencies