Volume 24, Issue 2 (2024)
MCEJ 2024, 24(2): 31-44 |
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Biglari A, nodeh S. Evaluation Possibility of Concrete Frames Rehabilitation with Off-Grade Steel Bracing. MCEJ 2024; 24 (2) :31-44
URL: http://mcej.modares.ac.ir/article-16-66411-en.html
URL: http://mcej.modares.ac.ir/article-16-66411-en.html
1- Assistant Professor, Department of Civil Engineering, Golestan University. , biglari.a@gmail.com
2- Master of Civil Engineering Student, Department of Civil Engineering, Golestan University.
2- Master of Civil Engineering Student, Department of Civil Engineering, Golestan University.
Abstract: (784 Views)
Steel bracing is known as one of the most effective systems resistant to lateral loads, and its use has been the subject of numerous studies to improve the lateral deformation tolerance of existing reinforced concrete frames. In this study, the seismic performance of steel bracing in the concentric plane in order to strengthen the existing reinforced concrete structures has been numerically investigated. A scaled reinforced concrete frame was modeled by finite element method by simple cross bracing. In the retrofitting of damaged reinforced concrete structures, attention should be paid to the continuity of service of the structure in structures of high importance. The important point in buildings of special importance such as hospitals and government buildings is that in such buildings the maintenance of the structure must be maintained at all hours. In addition, the implementation of in-plane bracing causes the destruction of intermediate frame components and can reduce the effective role of intermediate frame components in the seismic load of reinforced concrete frames. The interaction between the frame and the frame in seismic loading is an important issue that has been extensively focused on by various researches. Another important point is to pay attention to architectural issues and match the retrofit method with the aesthetic aspects of the structure. If there is an opening in the damaged frame, using the internal reinforcement method may cause problems in the opening space in the desired frame.
According to the mentioned points, in order to continue the service of the structure during the retrofit operation and to reduce the destruction operation in the intermediate frame components, the reinforcement member can be externally connected to the damaged frame. Therefore, in this study, in order to achieve the mentioned goals, the implementation of steel bracing outside the plane was also investigated using the numerical method and its Possibility was verified. The studied sample was subjected to lateral load by displacement control method by ABAQUS software and analyzed by quasi-static method. This enables a better understanding of the performance of frames strengthened with in-plane and out-of-plane steel braces and the evaluation of the proposed method. In this study, the models were examined in terms of deformation and cracking characteristics, hysteresis, lateral stiffness reduction and energy absorption capability.The results of this study showed that after strengthening with braces, there was no local rupture due to the application of lateral load in the place of the plastic joints of the frames. As a result of the application of lateral load, the normal moment frame specimen showed a more fragile hysteretic behavior. The maximum resistance value of the reinforced concrete frame in a certain displacement after strengthening increased to 2.5 times of its original sample and resulted in less stress concentration in the boundary elements compared to in-plane bracing. The amount of hardness created in the sample increased to 1.35 times of the original sample and the amount of energy absorption increased to 2.25 times of the original sample. The results obtained in hysteresis, stiffness reduction and energy absorption sections indicate the effective performance of the proposed method in strengthening damaged reinforced concrete structures.
According to the mentioned points, in order to continue the service of the structure during the retrofit operation and to reduce the destruction operation in the intermediate frame components, the reinforcement member can be externally connected to the damaged frame. Therefore, in this study, in order to achieve the mentioned goals, the implementation of steel bracing outside the plane was also investigated using the numerical method and its Possibility was verified. The studied sample was subjected to lateral load by displacement control method by ABAQUS software and analyzed by quasi-static method. This enables a better understanding of the performance of frames strengthened with in-plane and out-of-plane steel braces and the evaluation of the proposed method. In this study, the models were examined in terms of deformation and cracking characteristics, hysteresis, lateral stiffness reduction and energy absorption capability.The results of this study showed that after strengthening with braces, there was no local rupture due to the application of lateral load in the place of the plastic joints of the frames. As a result of the application of lateral load, the normal moment frame specimen showed a more fragile hysteretic behavior. The maximum resistance value of the reinforced concrete frame in a certain displacement after strengthening increased to 2.5 times of its original sample and resulted in less stress concentration in the boundary elements compared to in-plane bracing. The amount of hardness created in the sample increased to 1.35 times of the original sample and the amount of energy absorption increased to 2.25 times of the original sample. The results obtained in hysteresis, stiffness reduction and energy absorption sections indicate the effective performance of the proposed method in strengthening damaged reinforced concrete structures.
Keywords: strengthening, Reinforced concrete frame, Steel bracing, Off-grade bracing, Cyclic loading
Article Type: Original Research |
Subject:
Civil and Structural Engineering
Received: 2022/12/29 | Accepted: 2024/02/28 | Published: 2025/02/28
Received: 2022/12/29 | Accepted: 2024/02/28 | Published: 2025/02/28
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