Evaluation of earthquake ground motions to predict cracking response of gravity dams

Smooth design spectra are generally used to describe the seismic excitation imparted by the maximum design earthquake for safety evaluation of critical facilities such as concrete dams. When earthquake induced stresses exceed the elastic strength capacity of the structure, dynamic nonlinear analyses in the time-domain are recommended to determine the potential path of crack extension and failure mechanism. Spectrum-compatible ground motion acceleration time histories, that might be defined using different approaches, must then be specified as input to perform crack propagation analyses. However, the cracking response is sensitive to the details of the time variations of the input motions, This paper presents a study of the cracking response of gravity dams subjected to: (i) historical records scaled to the smooth spectrum intensity; (ii) spectrum-compatible accelerograms generated by random vibration theory; and (iii) spectrum-compatible accelerograms obtained from the modification of the Fourier spectrum coefficients of historical records while preserving the original phase angles. The crest displacements, the seismic energy response, and the cracking profiles are examined in parametric analyses to identify the type of input motion that is critical for the earthquake resistant design of gravity dams.