Volume 22, Issue 5 (2022)                   MCEJ 2022, 22(5): 125-140 | Back to browse issues page

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1- MSc Student, Department of Civil Engineering, Tafresh University, 39518-79611 Tafresh, Iran.
2- Assistant Professor, Department of Civil Engineering, Tafresh University, 39518-79611 Tafresh, Iran. , rajabi@tafreshu.ac.ir
Abstract:   (1053 Views)
Most seismic hazard assessments are usually performed only with consideration of the initial shock in the technical literature of structural and earthquake engineering. While the magnitude of aftershocks that occur after the main earthquake, may be enough strong to cause a lot of damage to the structures. Most aftershocks increase the structural damage caused by the main earthquake because of cumulative damage and increased vulnerability may seriously threaten the safety of residents. The structures are designed for solely a single earthquake – design earthquake –  based on the existing seismic design codes. For example, these codes did not provide specific values for the actual relative displacement under successive earthquakes to assess the structural damages. Therefore, considering the effect of multiple shocks consist of fore-shock and main-shock or main-shock and after-shock seems necessary. Moreover, the construction of a new building is not economic and requires a lot of time, which is not easily available to many communities. Hence, the design of structures considering the some capabilities such as replacement of damaged elements can improved significantly the performance of structures after severe successive earthquakes. However, most of the proposed structural systems are not generally repairable while replacing several damaged members under the earthquake, can be very economic and applicable. The linked column frame (LCF) as a relatively modern lateral bearing system, is a type of dual systems; the recent emergence of this structural system has reinforced the need for multiple seismic studies. For this reason, LCF is selected in this paper and the deflection amplification factor (Cd) for this system is evaluated under critical earthquakes with seismic sequences. This coefficient is calculated based on the linear displacements obtained from linear static analysis and actual values from nonlinear analysis. In this regard, 18 steel frames equipped by the linked column frame as lateral bearing system, with 3, 7, and 11 stories are designed based on the Iranian earthquake design code (Standard No. 2800, 4th version – 2014). These frames are implemented in Opensees software and have been subjected to linear static, linear, and nonlinear dynamic analyses using critical earthquakes with/ without seismic sequence phenomenon to calculate the deflection amplification factor (Cd) and Cd/R for each of them based on Uang methaod. In order to better investigation of the mentioned coefficient, the effect of various parameters such as the length of the connection beams as well as the flexural or shear behavior of the connection beams have been considered. Thus, after the evaluations, the findings indicate an increase in Cd and Cd / R values, for the linked column frame with the connected column exposed to successive earthquakes. The increase of this coefficient has been more in short-frame frames. So that the most increase which hase been related to the 3-story frame with shear behavior and 2-meter linked distance, is about 11 percentage under the successive earthquakes. Also, the average results which have been obtained from consecutive earthquakes reveal that the proposed values ​​for Cd coefficient in the technical literature are not sufficient, and larger values ​​have been demanded.
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Article Type: Original Research | Subject: Earthquake
Received: 2022/01/12 | Accepted: 2022/02/22 | Published: 2022/07/1

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