The Earthquake Engineering Online Archive

Numerical techniques for the evaluation of soil-structure interaction effects in the time domain

Bayo, Eduardo; Wilson, Edward L.

UCB/EERC-83/04, Earthquake Engineering Research Center, University of California, Berkeley, 1983-02, 173 pages (535/B15/1983)

A time domain finite element method that efficiently solves the three-dimensional soil-structure interaction problem is presented. In addition to all the factors currently considered by frequency domain approaches, this new method allows the consideration of the nonlinear effects in the structure and foundation (separation of base mat from soil or nonlinear material). The general equations of motion for the linear cases are expressed in terms of the relative displacements of the soil-structure system with respect to those of the nodes at the foundation level. This formulation allows the load vector to be an exclusive function of the free field accelerations at the soil-structure interface. The energy radiation through the boundaries of the finite element model is accounted for by using frequency-independent radiation boundaries obtained from a frequency-dependent boundary defined at the fundamental frequency of the soil-structure system. The soil-structure system is divided into substructures, the structure and the soil. The latter is modeled with three-dimensional solid elements in the near field and axisymmetric elements in the far field. A new method for the reduction in the number of degrees-of-freedom is presented. For linear problems, the present method becomes numerically far more efficient than the existing frequency domain approaches. The difference leads to substantial savings in computer time and storage.

Available online: http://nisee.berkeley.edu/documents/EERC/EERC-83-04.pdf (4 MB)