Earthquake analysis of concrete arch dams by non- orthogonal smeared crack model

摘要

A special 3-dimensional finite element program, based on fractured continuum models, is described and developed to study the seismic response of concrete arch dams. Two types of fixed smeared crack models; namely, a uni-directional and a non-orthogonal multi-directional, are incorporated in the program. Unloading after cracking is assumed to be either parallel to the initial elastic path or along a secant line from the point of unloading to the point of zero strain. The details of the formulation are presented and the accuracy of the models and their implementation are verified by analyzing a notched beam and comparing its results with available experimental data. Following the satisfactory results of the beam analysis, the program is applied to a practical problem, viz. the crack induced behavior of the 130 m high Shahid Rajaee arch dam in Iran, subjected to the Friuli-Tolmezzo earthquake. The results are compared with those obtained from a linear elastic analysis under the same excitation but without considering cracking. Based on the results, it is concluded that the uni-directional smeared crack approach produces a stiff response and is unable to properly redistribute the stresses through the structure after cracking. On the other hand, the non-orthogonal smeared crack model is capable of appropriate stress redistribution and produces a more realistic profile of stresses in the dam. It is also observed that a drift in the crest displacements is the prominent consequence of cracking of the dam.