Synthesizing Broadband Time-Histories at Near Source Sites; Case Study, 2003 Bam Mw6.5 Earthquake

The main objective of this article is to synthesize the 2003 Bam earthquake. A hybrid method is proposed for synthesizing the near-fault broadband timehistories; a theoretical green's function method and a stochastic finite-fault approach for generating time histories at low and high frequencies, respectively. A genetic algorithm is developed to optimize the differences between synthesized and recorded ground motions.

The proposed technique can be used for dynamic nonlinear analysis of structures and site specific hazard analysis of the regions with lack of sufficient data and also for retrofitting the damaged structures during Bam earthquake, particularly the well-known adobe buildings of Arg-e-Bam.     

Natural Frequency of Single Pier Bridges Considering Soil-Structure Interaction

Because of the crucial role of free vibration frequency of a structure (e.g., a bridge) in design procedure, more realistic estimation of the frequency ends up in safer and more optimized design. As obtaining the free vibration frequencies of a bridge, considering soil-pile group-structure interaction, provide more realistic values, development of an analytical model to obtain such free vibration frequencies is studied in this research work. Most researchers have studied models with a single pile foundation. The purpose of this study is to assess soil-structure interaction (SSI) effects on dynamic performance of pile group supported bridges. A new analytical model is proposed to predict seismic analysis of these bridges. Applying the dynamic equations of motion for the system, SSI effects have been estimated. Based on the suggested analytical model, a new approximate equation is proposed for calculating natural frequency of pile group supported bridges. Equation accuracy has been investigated by comparing the results with those achieved by previous studies. Most periods calculated by the approximate equation are similar to those given for other case studies, indicating that the model could be applicable to other projects. Since the proposed model is very similar to real soil-pile-pier systems, this approximate equation can be used in preliminary seismic design of bridges.