A. Kaveh , V.r. Mahdavi,
Volume 2, Issue 2 (6-2012)
Abstract
Endurance Time Acceleration Functions are specially predesigned intensifying excitation functions that their amplitude increases with time. On the other hand, wavelet transform is a mathematical tool that indicates time variations of frequency in a signal. In this paper, an approach is presented for generating endurance time acceleration functions (ETAFs) whose response spectrum is compatible with the European Code regulations (EC8) elastic spectrum. Method applied is a modification of data in time and frequency domain. For this purpose, wavelet transform has been used to decompose a series of random points to several levels such that each level covers a special range of frequency, then every level is divided into the numbers of equal time intervals and each interval of time is multiplied by a variable. Subsequently, the mathematical unconstrained optimization algorithm is used to calculate the variables and minimize error between response and target spectra. The prosed procedure is used in two methods. Then with two methods, two different acceleration functions are produced.
S. Shabankhah, A. Heidari, R. Kamgar,
Volume 11, Issue 4 (11-2021)
Abstract
Seismic analysis of structures is a process for estimating the response of structures subjected to earthquakes. For this purpose, the earthquake is analyzed using the wavelet theory. In this paper, the primary signal of the earthquake is decomposed through a discrete wavelet transform, and their corresponding response spectrum is obtained. Then, the percentage difference between the decomposed signals and the main one is computed. Therefore, for different earthquakes, a comparison between the response spectrum is studied in various types of dams. The acceleration, velocity, and displacement responses are computed and compared to achieve an appropriate level of decomposition, which can be used instead of the primary signal. Therefore, the decomposition process leads to attaining acceptable accuracy as well as low computational cost. The investigation revealed that the acceleration, velocity, and displacement responses spectrum are suitable up to the third level of decomposition for the small and medium dams, whereas for large dams, up to the fifth level of decomposition is suitable.
