• Journal of the Earthquake Engineering Society of Korea
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• v.10 no.3 s.49
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• pp.149-158
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• 2006

The reduced beam section (RBS) steel moment connection has performed well in past numerous tests. However there still remain several design issues that should be further examined. One such issue on RBS connection performance is the panel zone strength. Although a significant amount of test data are available, a specific recommendation for a desirable range of panel zone strength versus beam strength has yet to be proposed. In this paper, the effects of panel zone strength on the cyclic performance of RBS connection are investigated based on the available test database from comprehensive independent testing programs. A criterion for a balanced panel zone strength that assures sufficient plastic rotation capacity while reducing the amount of beam buckling is proposed. Numerical studies to supplement the test results are then presented based on the validated finite element analysis. Satisfactory numerical simulation achieved in this study also indicates that numerical analysis based on quality finite element modeling can supplement or replace, at least in part, the costly full-scale cyclic testing of steel moment connections.

• Steel and Composite Structures
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• v.32 no.4
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• pp.443-454
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• 2019

With the aim to put forward the analytical model for calculating the shear capacity of precast steel reinforced concrete (PSRC) beams, a static test on two full-scale PSRC specimens was conducted under four-point loading, and the failure modes and strain developments of the specimens were critically investigated. Based on the test results, a modified truss-arch model was proposed to analyze the shear mechanisms of PSRC and cast-in-place SRC beams. In the proposed model, the overall shear capacity of PSRC and cast-in-place SRC beams can be obtained by combining the shear capacity of encased steel shape with web concrete determined by modified Nakamura and Narita model and the shear capacity of reinforced concrete part determined by compatible truss-arch model which can consider both the contributions of concrete and stirrups to shear capacity in the truss action as well as the contribution of arch action through compatibility of deformation. Finally, the proposed model is compared with other models from JGJ 138 and AISC 360 using the available SRC beam test data consisting of 75 shear-critical PSRC and SRC beams. The results indicate that the proposed model can improve the accuracy of shear capacity predictions for shear-critical PSRC and cast-in-place SRC beams, and relatively conservative results can be obtained by the models from JGJ 138 and AISC 360.

• Journal of Korean Society of Steel Construction
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• v.16 no.2 s.69
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• pp.267-274
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• 2004

The objective of this study is to evaluate tensile load transmission capacity of H-shaped beam about design load by stud connector. The basic test of stud connecter was conducted and two specimens of full-scale size were tested under monotonic tensile loading condition. The parameter of tests is the size of the H-shaped beams. The results show that tensile load transmission capacity of H-shape beam about design load by stud connectors is excellent observing to the design code of steel structures of Architectural Institute of Korea.

• Earthquakes and Structures
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• v.3 no.1
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• pp.37-57
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• 2012

The behavior of beam-column joints in moment resisting frame structures is susceptible to damage caused by seismic effects due to poor performance of the joints. A good number of researches were carried out to understand the complex mechanism of RC joints considered in current seismic design codes. The traditional construction detailing of transverse reinforcement has resulted in serious joint failures during earthquakes. This paper introduces a new design philosophy involving the use of additional diagonal bars within the joint particularly suitable for low to medium seismic effects in earthquake zones. In this study, ten full-scale interior beam-column specimens were constructed with various additional reinforcement details and configurations. The results of the experiment showed that adding additional bars is a promising approach in reinforced concrete structures where earthquakes are eminent. In terms of overall cracking observation during the test, the specimens with additional bars (diagonal and straight) compared with the ones without them showed fewer cracks in the column. Furthermore, concrete confinement is certainly an important design measure as recommended by most international codes.

• Steel and Composite Structures
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• v.46 no.3
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• pp.417-433
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• 2023

The maximum ductility and cumulative ductility of connection joints of Buckling-Restrained Braced Frames (BRBF) are critical to the structural overall performance, which should be matched with the BRB ductility. The two-story and one-span BRBF with a one-third scale was tested under cyclic quasi-static loading, and the top-flange beam splice (TFBS) rotational connections were proposed and adopted in BRBF. The deformation capacity of TFBS connections was observed during the test, and the relationship between structural global ductility and local connection ductility was studied. The rotational capacity of the beam-column connections and the stability performance of the BRBs are highly relevant to the structural overall performance. The hysteretic curves of BRBF are stable and full under large displacement demand imposed up to 2% story drift, and energy is dissipated as the large plastic deformation developed in the structural components. The BRBs acted as fuses and yielded first, and the cumulative plastic ductility (CPD) of BRBs is 972.6 of the second floor and 439.7 of the first floor, indicating the excellent energy dissipation capacity of BRBs. Structural members with good local ductility ensure the large global ductility of BRBF. The ductile capacity and hysteretic behavior of BRBF with TFBS connections were compared with those of BRBF with Reduced Beam Section (RBS) connections in terms of the experimental results.

• Steel and Composite Structures
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• v.27 no.3
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• pp.337-353
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• 2018

In previous weak-axis moment connection tests, brittle fracture always initiated near the edge of the beam flange groove weld due to force flow towards the stiffer column flanges, which is the opposite pattern as strong-axis moment connections. As part of the China NSFC (51278061) study, this paper tested two full-scale novel weak-axis reduced beam section moment connections, including one exterior frame connection specimen SJ-1 under beam end monotonic loading and one interior frame joint specimen SJ-2 under column top cyclic loading. Test results showed that these two specimens were able to satisfy the demands of FEMA-267 (1995) or ANSI/AISC 341-10 (2010) without experiencing brittle fracture. A parametric analysis using the finite element software ABAQUS was carried out to better understand the cyclic performance of the novel weak-axis reduced beam section moment connections, and the influence of the distance between skin plate and reduced beam section, a, the length of the reduced beam section, b, and the cutting depth of the reduced beam section, c, on the cyclic performance was analyzed. It was found that increasing three parametric values reasonably is beneficial to forming beam plastic hinges, and increasing the parameter a is conducive to reducing stress concentration of beam flange groove welds while increasing the parameters b and c can only reduce the peak stress of beam flange groove welds. The rules recommended by FEMA350 (2000) are suitable for designing the proposed weak-axis RBS moment connection, and a proven calculation formulation is given to determine the thickness of skin plate, the key components in the proposed weak-axis connections. Based on the experimental and numerical results, a design procedure for the proposed weak-axis RBS moment connections was developed.

• Journal of Korean Society of Steel Construction
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• v.14 no.4
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• pp.557-566
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• 2002

This paper summarized the results of a full-scale cyclic seismic testing on four reduced beam section (RBS) steel moment connections. Specifically, these tests addressed a bolted web versus a welded web connection and strong versus medium panel zone (PZ) strength as key test variables. Specimens with medium PZ strength were designed to promote balanced energy dissipation from both PZ and RBS regions, in order to reduce the requirement for expensive doubler plates. Both strong and medium PZ specimens with welded web connection were able to provide sufficient connection rotation capacity required of special moment-resisting frames. On the other hand, specimens with bolted web connection performed poorly due to premature brittle fracture of the beam flange at the weld access hole. Unlike the case of web-welded specimens, specimens with cheaper bolted web connection could not transfer the actual plastic moment of the original (or unreduced) beam section to the column. No fracture occurred within the beam groove welds of any connection in this testing program. If fracture within the beam flange groove weld is avoided by using quality welding procedure as in this study, the fracture issue tends to move into the beam flange base metal at the weld access hole. Supporting analytical study was also conducted in order to understand the observed base metal fracture from the engineering mechanics perspective.

• Journal of the Earthquake Engineering Society of Korea
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• v.24 no.1
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• pp.29-37
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• 2020

This study is to investigate the effect of a retrofitted reinforced concrete frame with non-seismic details strengthened by embedded steel moment frames with an indirect joint, which mitigates the problems of the direct joint method. First, full-scale experiments were conducted to confirm the structural behavior of a 2-story reinforced concrete frame with non-seismic details and strengthened by a steel moment frame with an indirect joint. The reinforced concrete frame with non-seismic details showed a maximum strength of 185 kN at an overall drift ratio of 1.75%. The flexural-shear failure of columns was governed, and shear cracks were concentrated at the beam-column joints. The reinforced concrete frame strengthened by the embedded steel moment frames achieved a maximum strength of 701 kN at an overall drift ratio of 1.5% so that the maximum strength was about 3.8 times that of the specimen with non-seismic details. The failure pattern of the retrofitted specimen was the loss of bond strength between the concrete and the rebars of the columns caused by a prying action of the bottom indirect joint because of lateral force. Furthermore, methods are proposed for calculation of the specified strength of the reinforced concrete frame with non-seismic details and strengthened by the steel moment frame with the indirect joint.

• Advances in concrete construction
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• v.9 no.3
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• pp.313-326
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• 2020

Glass fiber-reinforced polymer (GFRP) bars have been introduced as an effective alternative for the conventional steel reinforcement in concrete structures to mitigate the costly consequences of steel corrosion. However, despite the superior performance of these composite materials in terms of corrosion, the effect of replacing steel reinforcement with GFRP on the seismic performance of concrete structures is not fully covered yet. To address some of the key parameters in the seismic behavior of GFRP-reinforced concrete (RC) structures, two full-scale beam-column joints reinforced with GFRP bars and stirrups were constructed and tested under two phases of loading, each simulating a severe ground motion. The objective was to investigate the effect of damage due to earthquakes on the service and ultimate behavior of GFRP-RC moment-resisting frames. The main parameters under investigation were geometrical configuration (interior or exterior beam-column joint) and joint shear stress. The performance of the specimens was measured in terms of lateral load-drift response, energy dissipation, mode of failure and stress distribution. Moreover, the effect of concrete damage due to earthquake loading on the performance of beam-column joints under service loading was investigated and a modified damage index was proposed to quantify the magnitude of damage in GFRP-RC beam-column joints under dynamic loading. Test results indicated that the geometrical configuration significantly affects the level of concrete damage and energy dissipation. Moreover, the level of residual damage in GFRP-RC beam-column joints after undergoing lateral displacements was related to reinforcement ratio of the main beams.

• Journal of Korean Society of Steel Construction
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• v.25 no.1
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• pp.103-114
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• 2013

Recently, there is a growing interest on sustainable connection system that makes it possible to reuse of main structural members by concentrating most of the damage in the frame caused by strong horizontal force, such as earthquake, to damper. In this study proposed a new type of damage-controlled connection system applying these concepts and analysed the major structural performance of the proposed system through the full-scale cyclic loading test and nonlinear finite element analyses. According to the result, it derived the optimal damper/beam strength ratio that minimize the damage of main members and satisfy at least the fully plastic moment of the beam. And it was to verify the possibility of applying as seismic connection details.