چكيده به لاتين
Determining the actual nonlinear behavior of structures is one of the main objectives of civil engineers. The MPA-Based IDA method is a novel idea to achieve the mensioned objective. In fact, the MPA-Based IDA is an alternative method for the laborious IDA (Incremental Dynamic Analysis) method. Inspite of resulting approximate outcomes, some benefites such as easiness, low cost procedure and high accuracy make the MPA-Based IDA method to an efficient and versatile analysis method. On the other hand, with recent progresses at engineering calculation, the necessity of considering all effective parameters increased. One of the substantial effective factors on the structural behavior is soil-structure interaction (SSI) effect. Subsoil could affect the structure responses by three manners, 1) Altering the stiffness and damping of the structure 2) Filtering the input earthquake record 3) Generating the possible movement and rotation at foundation.
In current research, it is intended to develop the MPA-Based IDA method for exerting the method on soil-structure systems. Afterwards, the developed method and also the exact IDA method will be used for analyzing the soil-structure systems considered in this study. The accuracy of proposed method is evaluated by comparing the results of developed MPA-Based IDA method with the results of exact IDA method.
In order to evaluate the SSI effect, a wide range of soils considered. Assumed soils are including loose sande, medium sand, medium-dense sand, dense sand, soft clay, medium clay, stiff clay and rigid based. This way seven types of sub-soil as well as rigid based situation are considered. Five concrete moment frames with different stories (3, 6, 9, 12 and 15 stories) are chosen to cover various height of structures. Considering five different frames and seven soil types leads to generating thirty-five soil-structure systems, these systems as well as five rigid based frames are evaluated herein. Exerting thirty records on aforemensioned systems leads to 1200 IDA analyses and 1200 MPA-Based IDA analyses.
The verification of numerical models has been done by comparing the obtained results with the outcomes of a shaking table test. Moreover, the proposed method is verified by comparing the proposed method results with the outcomes of the exact IDA method.
Evaluating the results reveals the effect of existing each assmed soil types beneath any of given structures. The fragility curves were generated for soil-structure systems and for rigid-based systems as well, the vulnerability of structures is evaluated through that curves.
Results reveal that the effect of SSI is highly dependant to the specifications of structure, soil and input earthquake. However, general speaking it could be said that the SSI effect decreases with increasing structure height. In the case of sandy soils, it could be said that the looser the soil the more effect of the SSI; however, in the case of clayey soil the medium clay leads to the most effect of SSI. Moreover, the outcomes show that the proposed method is able to approximate acceptable response of soil-structure systems with high accuracy, and requires much less calculation in compare with the IDA method and has a low cost procedure.
