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Ren Tinawi Marc Sarrazin Andr Filiatrault 《Soil Dynamics and Earthquake Engineering》1993,12(8):469-477
The 1990 edition of the National Building Code of Canada (Associate Committee of the National Building Code, National Research Council, Ottawa, 1990) makes a clear distinction between eastern and western Canada in terms of seismic acceleration and velocity zones. While it is well established that ground motions can be amplified significantly through loose clay deposits, no results are available that take into consideration the typical high frequency content of ground motions in eastern Canada. This paper develops ground amplification curves for clays having depths between 10 and 70 m excited by typical eastern Canadian ground motions scaled to two different values of peak horizontal accelerations. Simplified free-field spectral design curves, which could be used by structural designers, are proposed. The curves show that maximum spectral accelerations occur for structural periods between 0.2 and 0.5 s. In addition, soil depth does not appear to be an important parameter controlling the response of typical clay deposits in eastern Canada. 相似文献
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A new analytical development of the seismic hydrodynamic pressure inside pre-existing cracks on the upstream face of concrete dams is presented. The finite control volume approach is utilized to derive an expression for the seismic hydrodynamic pressure using the continuity principle and the linear momentum theorem for the fluid inside the crack. The derived pressure expression is a function of the relative crack-opening acceleration and velocity. The acceleration and velocity terms are then recast in the form of added mass and damping matrices which can then be included at the nodes inside the discrete crack of a finite element model. This procedure linearizes the solution of the problem. A dam, 55 m high and having an initial crack opening of 2 mm at the base or near the crest and subjected to two different accelerograms, is analysed. For high-frequency ground motion, the seismic hydrodynamic pressure inside the crack, at the base of the dam, appears to be 50 per cent higher than the corresponding hydrostatic pressure. 相似文献
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This paper discusses the local approach of fracture using damage mechanics concepts to evaluate the seismic response of concrete gravity dams. A constitutive model for plain concrete, subjected to tensile stresses, is presented. The mesh-dependent hardening technique is adopted such that the fracture energy dissipated is not affected by the finite element mesh size. The model is implemented in conjunction with the Hilber, Hughes Taylor alpha algorithm for time marching. Koyna dam is utilized to validate the proposed formulation. The importance of initial damage prior to the advent of an earthquake is also investigated. A 60 m concrete gravity dam is therefore selected and subjected to ground motion typical of eastern North America. Five scenarios of initial damage are presented and the results confirm the importance of accounting for the initial state for the seismic safety evaluation of an existing dam. 相似文献
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