Search

A non-linear finite element (FE) model is presented to account for soil column effects on strong ground motion. A three-dimensional bounding surface plasticity model with a vanishing elastic region, appropriate for non-liquefiable soils, is formulated to accommodate the effects of plastic deformation right at the onset of loading. The elasto-plastic constitutive model is cast within the framework of a FE soil column model, and is used to re-analyse the downhole motion recorded by an array at a Large-Scale Seismic Test (LSST) site in Lotung, Taiwan, during the earthquake of 20 May 1986; as well as the ground motion recorded at Gilroy 2 reference site during the Loma Prieta earthquake of 17 October 1989. Results of the analysis show maximum permanent shearing strains experienced by the soil column in the order of 0.15 per cent for the Lotung event and 0.8 per cent for the Loma Prieta earthquake, which correspond to modulus reduction factors of about 30 and 10 per cent respectively, implying strong non-linear response of the soil deposit at the two sites. Copyright © 2000 John Wiley & Sons, Ltd.