چكيده به لاتين
Current research has investigated the combined effects of in-span hinges and level of irregularity on the seismic performance of multi-frame bridges considering the soil-structure interaction. Although previous studies have proposed methodologies so as to quantify the irregularity of the bridges in terms of global regularity index, it still remains unclear how to determine the distribution of irregularity along a bridge, as well as to discover the irregularity sources. Generally, most related studies have been conducted based on the assumption that the bridges are located on a rigid base and therefore, the seismic performance as well as the regularity level of soil-structure systems were igored. This research project is intended to develop a quantitative vector regularity criterion for single and multi-frame bridges based on the modified correlation function for spatial locations of scaled mode shapes of deck-alone and whole bridge. The proposed criterion calculates two types of regularity indices, namely, local (LRI) and global regularity indices (GRI). The GRI is a scalar value representing the overall regularity of the entire bridge, whereas the LRI highlights vector irregularity distribution along the bridge. Since the deck discontinuity due to the in-span hinges is one of the leading causes for irregularity, the efficiency of proposed index has been investigated in the cases of multi-frame bridges as well. Based on the results, this index can be extended to the soil-structure systems as well. Therefore, the seismic behavior of multi-frame bridges in the cases of with and without soil-structure interaction can be estimated by using proposed index. Based on design codes, the regularity classification of the bridges plays a major role in determining the proper method of analysis. On the other hand, there are ambiguities in calculating both regularity index and the nonlinear to linear displacement ratio of multi-frame bridges; therefore, the main focus of this dissertation is to evaluate the regularity degree and inelastic displacement ratio for multi-frame systems. To this aim, four classes of single and multi-frame bridges with inelastic behavior located on four different soil types with various shear wave velocities are considered. With regarding to the results, this research confirms that the multi-frame bridges are associated with less values of GRI and LRI in comparison with their single-frame counterparts. In general, the proposed local and global regularity indices of soil-structure systems increase with decreasing in the soil shear wave velocity. Accordingly, in-span hinges, dimensionless frequency (a0) and the level of regularity are the main parameters affecting the seismic performance of multi-frame bridges. The results reveal that considering merely the site effects in estimating the seismic performance of multi-frame bridges, leads to completely different results of structures located on soft soils comparing to the responses of structures located on hard and sedimentary soils. However, considering the soil-structure interaction reduces this difference. Based on the obtained results, it can be inferred that the performance and regular indices of single-frame bridges cannot be generalized to estimate the parameters and behavior of multi-frame bridges. Therefore, multi-frame bridges need to be investigated in detail so as to validate the special design requirements recommended by design codes.