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Equivalent static load and dynamic analyses methods are usually used for designing structures under and subjected to earthquake excitations. Estimation of site response from an earthquake is fundamental step to anticipate the possible damages and then to try to mitigate them. In this paper, the effect of nonlinearity on site response analyses summarized and evaluating ground surface response taking into account the local soil and subsurface soils properties for the proposed bridge over the river at Sirdjan Boulevard road subjected to earthquake vibration and provokes with assumption of rigid (viscoelastic) and elastic half space bedrock and quantify the site effect on the surface over a number of geotechnical areas has been notified. First, by field investigation, the required data were collected and by primary processing the acceptable data were selected. Then, in nonlinear analysis, for elastic and rigid half space bedrock, standard hyperbolic model was selected and executed, and then the results were compared to each other. The critical point of this work was to develop and use a computer code by the authors, named the "Abbas Converter", with several advantages, such as work and quick installation, operating as a connecter function between the used softwares and generating the input data corresponding to defined format for them. Its output results can easily be exported to the other used softwares in this study. This code can make and render this study more easily than the previous softwares have done, and take over the encountered problem. This study clearly showed the applicability of the "Abbas Converter" for evaluation of site response with bedrock-type assumption on soil behavior under the earthquake excitations. The proposed scheme is used to analyze the ground motion data from the Bam earthquake in Kerman Province, Iran (2003, M w 6.5).

The aim of this study is to illustrate the soil conditions encountered at the proposed bridge sites to analyze and evaluate the test conducted, submit recommendations regarding foundation design. At first by field investigation, the required data was collected and after primary processing the acceptable data was selected. For nonlinear analysis of elastic and rigid half space bed rock, standard hyperbolic model was selected and performed, and the results were compared. The study clearly showed that the effect of bed rock on soil behavior during earthquake is one of the main factors controlling prediction of ground response. A critical aspect of this work was to develop and use a computer code "Abbas Converter" developed by the authors that has several advantages, such as quick installation, acting as a connecter function between the used softwares which can generate the input data corresponding to a defined format and finally, the results of this computer code can be easily exported to the other softwares used in this study. Moreover this code can make it easy to solve the problems encountered.Keyword: Nonlinear time domain analysis, "Abbas converter", Elastic and rigid half space Bed rock, Iran. epicentral distance. The ideal solution for such a problem is to use a database of recorded strong motions and group the accelerograms that have similar source, path and site effects, which in practice is not available. An alternative way of tackling this problem is based on computer codes, developed from the knowledge of the seismic source process and the propagation of seismic waves, that can simulate the ground motion associated with the given earthquake scenario (Romanelli and Vaccari, 1999;Park and Hashash, 2004;Arslan and Siyahi, 2006).Traditionally, earthquake ground motions are predicted in two stages. In the first stage, an attenuation relationship is used to relate the earthquake magnitude (which is typically measured from very low-frequency surface waves) to a much higher frequency parameter such as the peak ground acceleration (PGA), or the response spectral acceleration during low magnitude. In the second stage, a response spectrum model is used in conjunction with the highfrequency parameter to define the design response spectrum. Thus, the ground motion properties have been extrapolated twice in the frequency domain, namely from the low-frequency range to the high-frequency range, and vice versa. Such a response spectrum model though outdated is still adopted around the world (Lam et al., 2000).