• Earthquakes and Structures
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• v.15 no.2
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• pp.113-122
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• 2018

This study presents a new beam-column model comprising material nonlinearity and joint flexibility to predict the nonlinear response of reinforced concrete structures. The nonlinear behavior of connections has an outstanding role on the nonlinear response of reinforced concrete structures. In presented research, the joint flexibility is considered applying a rotational spring at each end of the member. To derive the moment-rotation behavior of beam-column connections, the relative rotations produced by the relative slip of flexural reinforcement in the joint and the flexural cracking of the beam end are taken into consideration. Furthermore, the considered spread plasticity model, unlike the previous models that have been developed based on the linear moment distribution subjected to lateral loads includes both lateral and gravity load effects, simultaneously. To confirm the accuracy of the proposed methodology, a simply-supported test beam and three reinforced concrete frames are considered. Pushover and nonlinear dynamic analysis of three numerical examples are performed. In these examples the nonlinear behavior of connections and the material nonlinearity using the proposed methodology and also linear flexibility model with different number of elements for each member and fiber based distributed plasticity model with different number of integration points are simulated. Comparing the results of the proposed methodology with those of the aforementioned models describes that suggested model that only uses one element for each member can appropriately estimate the nonlinear behavior of reinforced concrete structures.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.20 no.2
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• pp.165-179
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• 2007

For the purpose of optimum design of reinforced concrete structures, pre-determined section database of column and beam are constructed and arranged in order of the resisting capacity. Then, regression equations representing the relation between section number and section resisting capacity are derived. In advance, effective optimization algorithms which search optimized solution quickly using direct search method from these database are proposed. In practice, from the fact that engineers conduct member design close to capacity optimization rather than cost optimization, both capacity and cost optimization using proposed algorithms are performed, and the review for the obtained results are followed. Moreover, the investigation for the applicability and effectiveness of the Introduced design procedure is conducted through correlation study for example structures. Because of no restriction in constructing objective functions with very simple optimization processes and fast convergence, the introduced method can effectively be used in the preliminary design stage. Especially, selected solutions from database are directly applicable in practice because these sections already satisfy all the requirements in design codes and practical restrictions.

• Journal of the Earthquake Engineering Society of Korea
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• v.27 no.1
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• pp.37-47
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• 2023

A new clamped mechanical splice system was proposed to develop structural performance and constructability for precast concrete connections. The proposed mechanical splice resists external loading immediately after the engagement. The mechanical splices applicable for both large-scale rebars for plants and small-scale rebars for buildings were developed with the same design concept. Quasi-static lateral cyclic loading tests were conducted with reinforced and precast concrete members to verify the seismic performance. Also, shaking table tests with three types of seismic wave excitation, 1) random wave with white noise, 2) the 2016 Gyeongju earthquake, and 3) the 1999 Chi-Chi earthquake, were conducted to confirm the dynamic performance. All tests were performed with real-scale concrete specimens. Sensors measured the lateral load, acceleration, displacement, crack pattern, and secant system stiffness, and energy dissipation was determined by lateral load-displacement relation. As a result, the precast specimen provided the emulative performance with RC. In the shaking table tests, PC frames' maximum acceleration and displacement response were amplified 1.57 - 2.85 and 2.20 - 2.92 times compared to the ground motions. The precast specimens utilizing clamped mechanical splice showed ductile behavior with energy dissipation capacity against strong motion earthquakes.

• Journal of the Earthquake Engineering Society of Korea
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• v.28 no.2
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• pp.85-92
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• 2024

This study presents code-compliant seismic details by addressing dry mechanical splices for precast concrete (PC) beam-column connections in the ACI 318-19 code. To this end, critical observations of previous test results on precast beam-column connection specimens with the proposed seismic detail are briefly reported in this study, along with a typical reinforced concrete (RC) monolithic connection. On this basis, nonlinear dynamic models were developed to verify seismic responses of the PC emulative moment-resisting frame systems. As the current design code allows only the emulative design approach, this study aims at identifying the seismic performances of PC moment frame systems depending on their emulative levels, for which two extreme cases were intentionally chosen as the non-emulative (unbonded self-centering with marginal energy dissipation) and fully-emulative connection details. Their corresponding hysteresis models were set by using commercial finite element analysis software. According to the current seismic design provisions, a typical five-story building was designed as a target PC building. Subsequently, nonlinear dynamic time history analyses were performed with seven ground motions to investigate the impact of emulation level or hysteresis models (i.e., energy dissipation performance) on system responses between the emulative and non-emulative PC moment frames. The analytical results showed that both the base shear and story drift ratio were substantially reduced in the emulative system compared to that of the non-emulative one, and it indicates the importance of the code-compliant (i.e., emulative) connection details on the seismic performance of the precast building.

• Journal of the Korea Concrete Institute
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• v.23 no.6
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• pp.711-722
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• 2011

Beam-column gravity or Intermediate Moment frames subjected to unexpected large displacements are vulnerable when no seismic details are provided, which is typical. Conversely, economic efficiency of those frames is decreased if unnecessary special detailing is applied as the beam and column size becomes quite large and steel congestion is caused by joint transverse reinforcement in beam-column connections. Moderate seismic design is used in Korea for beam-column connections of buildings with structural walls, which are to be destroyed when the unexpected large earthquake occurs. Nonetheless, performance of such beamcolumn connections may be substantially improved by the addition of steel fibers. This study was conducted to investigate the effect of steel fibers in reinforced concrete exterior beam-column connections and possibility for the replacement of some joint transverse reinforcement. Ten half-scale beam-column connections with non-seismic details were tested under cyclic loads with two cycles at each drift up to 19 cycles. Main test parameters used were the volume ratio of steel fibers (0%, 1%, 1.5%) and joint transverse reinforcement amount. The test results show that maximum capacity, energy dissipation capacity, shear strength and bond condition are improved with the application of steel fibers to substitute transverse reinforcement of beam-column connections. Furthermore, several shear strength equations for exterior connections were examined, including the proposed equation for steel fiber-reinforced concrete exterior connections with non-seismic details.