• Earthquakes and Structures
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• v.20 no.2
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• pp.133-148
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• 2021

The paper presents a simplified force-based seismic design procedure for the preliminary design of steel haunch retrofitting for the seismic upgrade of deficient RC frames. The procedure involved constructing a site-specific seismic design spectrum for the site, which is transformed into seismic base shear coefficient demand, using an applicable response modification factor, that defines base shear force for seismic analysis of the structure. Recent experimental campaign; involving shake table testing of ten (10), and quasi-static cyclic testing of two (02), 1:3 reduced scale RC frame models, carried out for the seismic performance assessment of both deficient and retrofitted structures has provided the basis to calculate retrofit-specific response modification factor Rretrofitted. The haunch retrofitting technique enhanced the structural stiffness, strength, and ductility, hence, increased the structural response modification factor, which is mainly dependent on the applied retrofit scheme. An additional retrofit effectiveness factor (ΩR) is proposed for the deficient structure's response modification factor Rdeficient, representing the retrofit effectiveness (ΩR=Rretrofitted /Rdeficient), to calculate components' moment and shear demands for the retrofitted structure. The experimental campaign revealed that regardless of the deficient structures' characteristics, the ΩR factor remains fairly the unchanged, which is encouraging to generalize the design procedure. Haunch configuration is finalized that avoid brittle hinging of beam-column joints and ensure ductile beam yielding. Example case study for the seismic retrofit designs of RC frames are presented, which were validated through equivalent lateral load analysis using elastic model and response history analysis of finite-element based inelastic model, showing reasonable performance of the proposed design procedure. The proposed design has the advantage to provide a seismic zone-specific design solution, and also, to suggest if any additional measure is required to enhance the strength/deformability of beams and columns.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.37 no.5
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• pp.301-308
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• 2024

During earthquakes, buildings can suffer damage ranging from minor to severe, potentially leading to collapses and resulting in loss of life and property. To mitigate these risks, it is essential to evaluate the seismic performance of buildings. Current seismic performance evaluation techniques require significant time as they focus on individual buildings. Therefore, there is a need to develop evaluation techniques that can be applied on a regional scale. This study proposes a single-degree-of-freedom model with a nonlinear shear spring to assess the seismic performance and plan the reinforcement of reinforced concrete residential buildings. The nonlinear shear spring, defined by the T-SR-μ parameter, is used to simulate the nonlinear response of the structure. By applying 100-PEER ground motions to this model, the seismic performance of the buildings was evaluated based on the maximum inter-story drift ratio response. The applicability of the proposed technique was confirmed by comparing it with detailed models, where both models assessed the seismic performance of the buildings at similar levels. This results demonstrate that the proposed method can accurately predict the seismic performance of actual buildings.