The Earthquake Engineering Online Archive

Hybrid modelling of soil-structure interaction in layered media

Tzong, Tsair-jyh; Penzien, Joseph

UCB/EERC-83/22, Earthquake Engineering Research Center, University of California, Berkeley, 1983-10, 148 pages (535/T988/1983)

In this study, the hybrid modeling approach, which effectively solves the soil-structure interaction problems, is extended for use in layered soil media. This approach partitions the entire structure-soil system into a near field and a far field with a smooth interface. The near field, which consists of the structure and a portion of its surrounding soil, is modeled using the finite element method. The far field, which is responsible for energy traveling away from the near field, is represented by an impedance model. Two analytical methods, appropriate for different layered soil systems, are employed to simulate the semi-infinite far-field region. The system identification method, which determines the approximate far-field impedance functions along the interface between the near and far fields, is applied to the single-layer halfspace. A boundary solution method is developed to calculate the exact far-field impedance matrix for cases involving layers of soil having a rigid lower boundary. Using this method, the authors combine the theoretical solution of the far field with the near-field finite elements via the variational principle. The dynamic behavior of the infinite rigid strip on a single-layer halfspace is determined. The modified Gauss-Newton method, which considers the second derivatives of the proposed error function, is applied to systematically identify the far-field impedance functions for the plane-strain case in the single-layer halfspace. Numerical results are obtained using the identified impedance functions. The principle of the virtual work employed in the far field and the variational principle employed in the near field constitute the boundary solution method. The dynamic behavior of the infinite rigid strip and the circular disk on the layers of soil with a rigid lower boundary is evaluated. This makes it possible to generate a far-field impedance matrix using the boundary solution method, which successfully accounts for energy traveling away from the structure, waves reflecting and refracting from the layer interfaces, and waves reflecting from the rigid lower boundary. The effectiveness and efficiency of the hybrid modeling for soil-structure interaction analysis in layered media are demonstrated by simulating the far field using the system identification method and the boundary solution method for different aforementioned soil conditions.

Available online: http://nisee.berkeley.edu/documents/EERC/EERC-83-22.pdf (4 MB)