Document Type : Articles
Authors
1
Department of Civil Engineering, Semnan University, Semnan, Iran
2
International Institute of Earthquake Engineering and Seismology, Tehran, Iran
3
Department of Structural Engineering, Building & Housing Research Center, Tehran, Iran
4
Qazvin Branch Islamic Azad University, Qazvin, Iran
Abstract
In masonry buildings, walls are the main structural members that deal with lateral forces. For seismic evaluation and reinforcement of these walls, there is no appropriate algorithm for the modelling of these unreinforced walls as well as single and double sided shotcrete reinforced walls.
The necessity of a highly specialized software has made the behavior analysis, seismic optimization or design of buildings having reinforced or unreinforced masonry walls to be impractical for most engineers. Development of a process for the use of common software will solve the problem and also make it possible to model reinforced and unreinforced masonry walls in semi-frame building or engineering. In this study, by considering the laboratory results of 12 reinforced and unreinforced walls subjected to cyclic load, the optimal parameter values for the best calibration of the modeling results with the existing laboratory results have been extracted.
The present research has modelled unreinforced and reinforced masonry walls. Given that most common designing software used by construction engineers lack proper elements that enables them to easily model masonry elements just like concrete and steel elements; thus, it is not possible to directly analyze the building in which there are masonry wall members. The solutions that are commonly used are either the use of complex modelling software which are not suitable for use in daily engineering offices applications. The behavior of walls are estimated in individual software and their effect is included in common analytical software that will surely cause a decrease in the accuracy of the results due to the lack of a possibility for considering the interactions. Results of the research are briefly as follows:
1. Extraction of parameters optimal values for the best calibration of software modelling results with laboratorial results.
2. Evaluation of the modelling capability of unreinforced and shotcrete single and double sided reinforced walls in common engineering analysis and design software
The main parameters that control the cyclic behavior of masonry walls in software with laboratorial results are as follows:
1. The best match with cyclic curves obtained from unreinforced brick walls experiments is obtained when in the computer model, isotropic masonry behavior, Takeda masonry hysteresis cycle type, shell section and 45 degree masonry element angle are obtained by considering the effect of dead load and applying Drager-Prager coefficients.
2. The best match of cyclic curves obtained from analytical results with the results obtained from single sided reinforced brick walls experiments, is obtained when the behavior of masonry and concrete materials is considered as isotropic, the behavior of rebar is considered "uniaxial", type of masonry and concrete materials hysteresis cycle is considered as Takeda and rebar are considered as kinematic. The section type for each of the three types of shell materials must be 45 degree for masonry materials, 0 degree for concrete materials and 0 and 90 degrees for horizontal and vertical rebar layers. The effect of dead load and the effect of Drager-Prager coefficients for masonry and concrete materials are also considered.
3. The best match for cyclic curves obtained from analytical results with double sided reinforced experiments is achieved in the characteristics of the materials, according to line 2. Naturally, in this state, characteristics for two concrete layers, two horizontal rebar layers and two vertical rebar layers are used.
In the second section of the results, we have evaluated the modelling capability of unreinforced and reinforced walls in common analytical and design engineering software.
Given that the six main parameters of strength and yield drift, maximum strength and its corresponding drift and the ultimate strength and drift are the main indicators in the curve of the members' behavior, in this paragraph, the results of the comparison of analytical estimation with laboratorial estimations about these six fold parameters are given.
In the final section of this research, the efficiency of the masonry walls optimization methods has been evaluated.
For proper selection of optimization methods, having a view of the probable effect of each method on the six fold behavioral characteristics can be a big help for a designer. Therefore, the designer can select a suitable option to improve a behavioral weakness in a wall. In this section, the ratio of each parameter in the reinforced wall to that parameter's value in its corresponding reference wall has been briefly given.
1. Single sided shotcrete reinforcement, increases the strength by 1.5 to 3 times the reference samples. While the analytical estimation of this value is about 1.5 to 3.5 times the laboratorial values.
2. Single sided shotcrete reinforcement increases the drift by 1.5 to 3 times the reference samples. While in the analytical estimation, this ratio has been decreased or increased by almost 50%.
3. Double sided shotcrete reinforcement increases the strength by 3 to 7 times the reference samples. While the analytical estimation of this value is about 2 to 3 times the laboratorial values.
4. Double sided shotcrete reinforcement increases the drift by 0.6 to 1.7 times the reference samples. While in the analytical estimation, this ratio has been decreased by about 30%.
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