• Journal of the Earthquake Engineering Society of Korea
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• v.7 no.3
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• pp.69-77
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• 2003

This paper presents test results on eight reduced beam section(RBS) steel moment connections. The testing program addressed bolted versus welded web connection and panel zone(PZ) strength as key variables, Specimens with medium PZ strength were designed to promote energy dissipation from both PZ and RBS regions such that the requirement for expensive doublet plates could be reduced. Both strong and medium PZ specimens with a welded web connection were able to provide satisfactory connection rotation capacity for special moment-resisting frames. On the other hand, specimens with a bolted web connection performed poorly due to premature brittle fracture of the beam flange of the weld access hole. If fracture within the beam flange groove weld was avoided using quality welding, the fracture tended to move into the beam flange base metal of the weld access hole. Plausible explanation of a higher incidence of base metal fracture in bolted web specimens was presented. The measured strain data confirmed that the classical beam theory dose not provide reliable shear transfer prediction in the connection. The practice of providing web bolts uniformly along the beam depth was brought into question. Criteria for a balanced PZ strength improves the plastic rotation capacity while reduces the amount of beam distortion ore also proposed.

• Steel and Composite Structures
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• v.9 no.5
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• pp.419-444
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• 2009

Flange and web local buckling in beam plastic hinge regions of steel moment frames can prevent beam-column connections from achieving adequate plastic rotations under earthquake-induced forces. Reducing the flange-web slenderness ratios (FSR/WSR) of beams is the most effective way in mitigating local member buckling as stipulated in the latest seismic design specifications. However, existing steel moment frame buildings with beams that lack the adequate slenderness ratios set forth for new buildings are vulnerable to local member buckling and thereby system-wise instability prior to reaching the required plastic rotation capacities specified for new buildings. This paper presents results from a research study investigating the cyclic behavior of steel I-beams modified by a welded haunch at the bottom flange and reinforced with glass fiber reinforced polymers at the plastic hinge region. Cantilever I-sections with a triangular haunch at the bottom flange and flange slenderness ratios higher then those stipulated in current design specifications were analyzed under reversed cyclic loading. Beam sections with different depth/width and flange/web slenderness ratios (FSR/WSR) were considered. The effect of GFRP thickness, width, and length on stabilizing plastic local buckling was investigated. The FEA results revealed that the contribution of GFRP strips to mitigation of local buckling increases with increasing depth/width ratio and decreasing FSR and WSR. Provided that the interfacial shear strength of the steel/GFRP bond surface is at least 15 MPa, GFRP reinforcement can enable deep beams with FSR of 8-9 and WSR below 55 to maintain plastic rotations in the order of 0.02 radians without experiencing any local buckling.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.5A
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• pp.665-672
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• 2008

In the study herein, the fatigue test was conducted on the fillet welds of the load carrying cruciform joint, which is frequently used in the steel structures such as bridges, ships, etc. In addition, the fatigue strength was analyzed with respect to the different post-weld treatment. The treatment methods used include Toe Grinding, TIG Dressing, and Weld Profiling. The fatigue test was under constant amplitude with repeated load for these test specimens. In the load carrying full penetration fillet welded joints, regardless the conduction of the post-weld treatment or not, they all secured the fatigue strength of category "F", which exceeds the fatigue design specifications of BS Code. In the comparison of the fatigue strength upon the post-weld treatment, the fatigue strength tends to increase according to the order: Toe Grinding, TIG Dressing, and Weld Profiling.

• Journal of Korean Society of Steel Construction
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• v.10 no.4 s.37
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• pp.629-639
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• 1998

This paper summarizes the results of full-scale cyclic seismic performance tests on three column-tree type steel moment connections. Each test specimen consisted of a $H-600{\times}200$ beam and a $H-400{\times}400$ column of SS41 (SS400). Key parameter included was column PZ (panel zone) strength relative to beam strength. The seismic performance of specimen with stronger PZ tended to be inferior. Total plastic rotations available in the specimens ranged from 1.8 to 3.0 (% rad). The limited test results in this study seem to support the speculation that permitting PZ yielding shall be more beneficial to enhancing total plastic rotation capacity of the moment connection. Beam flange fracture across the heat affected zone and divot-type pullout of the column flange were observed in the tests. A conceptual mechanical model consistent with observed test results was also sought.

• Journal of Korean Society of Steel Construction
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• v.22 no.4
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• pp.305-312
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• 2010

The objective of this paper is to examine the structural performance of steel moment-resisting frames on the various connection details of Seismic Wide-flanged Beam-to-Rectangular Steel Tube Column connections. Although compared to an H-shaped steel tube, a rectangular steel tube has many advantages and is more efficient, its application is limited due to the lack of experience in using it and the connection details. Existing steel moment connections using the rectangular steel tube are mainly used through plate diaphragms. The processing of construction of the rectangular steel tube is so complicated that it is hard to apply it in the field. In this study, the structural performance and the earthquake capacity of the connection details that do not cut the rectangular steel tube column were investigated. A comparative analysis of the strength, rigidity, and energy absorption capacity of the welded connection details using an end-plate and a haunch was also performed.

• Journal of Korean Society of Steel Construction
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• v.28 no.4
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• pp.231-242
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• 2016

Earthquake resistance of RC column-steel beam (RCS) joints with simplified details were studied. Simplified details are necessary for large columns to improve the productivity and constructability. To strengthen the beam-column joint, the effects of transverse beams, studs, and U-cross ties were used. Four 2/3 scale interior RCS connections were tested under cyclic lateral loading. The specimens generally exhibited good deformation capacity exceeding 4.0% story drift ratio after yielding of both beam and beam-column joint. Ultimately, the specimens failed by shear mechanism of the joint panel. The test strengths were compared with the predictions of existing design methods.

• Journal of Korean Society of Steel Construction
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• v.20 no.6
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• pp.829-838
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• 2008

In this study, cyclic tests of beam-column connections composed with members applicable to the domestic low-middle rise steel buildings were conducted to develop seismic connection details and its evaluation. Connection types and material properties of the steel were testing variables and the difference between the newly developed seismic rolled section (SHN490) and existing rolled section (SM490) was also investigated. Distributions of the yield strength and the ultimate strength of the SHN490 rolled section were relatively uniform comparing to those of the SM490 rolled section Brittle fracture in the weldments of the test specimens was not observed. Instead, fracture occurred at heat-affected zones or the stress-concentrated point near the weld access hole of the beam flanges. In the case of identical rolled-section specimens, the rotational capacity and dissipated energy of the WUF-W connection was larger than those of the WUF-B connection. In the case of identical connection types, the rotational capacity and dissipated energy of the SHN490 section connection was larger than those of the WUF-B section connection.

• International journal of steel structures
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• v.18 no.5
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• pp.1639-1653
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• 2018

Bolted connections are suitable due to high quality prefabrication in the factory and erection in the workplace. Prefabrication and modularization cause high speed of erection and fabrication, high quality and quick return of investment. Their technical hitches transportation can be removed by prefabrication of joints and small fabrication of components. Box-columns are suitable members for bolted structures such as welded steel structures with moment frames in two directions etc., but their continual fabrication in multi-story buildings and performing the internal continuity plate in them will cause some practical dilemmas. The details of the proposal technique introduced here, is to remove such problems from the box columns. Besides, some other advantages include new prefabricated bolted beam-to-column connections referred to BBCC. This connection is a set of plates joined to columns, beams, support, and bolts. For a better understanding of its fabrication and erection techniques, two connection and one structural maquettes are made. The present work aims to study the cyclic behavior of connection numerically. To verify the accuracy of model, a similar tested connection was modelled. Its verification was then made through comparison with test results. The behavior of connection was evaluated for an exterior connection using three different support shapes. The effects of support shapes on rigidity, ductility, rotation capacity, maximum strength, four rad rotation strength were compared to those of the AISC seismic provision requirements. It was found that single beams support has all the AISC seismic provision requirements for special moment frames with and without a continuity plate, and box with continuity plate is the best support in the BBCC connection.

• Journal of Korean Society of Steel Construction
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• v.17 no.3 s.76
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• pp.325-335
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• 2005

This study tackles the development of an improved detail of partially restrained CFT square column-to-beam connection and the evaluation of its mechanical behavior under monotonic loading. The connection is designed to strengthen shearing capacity at the bottom of the connection due to the ultimate behavior of PR-CC by its detail of the bottom connection and simplify the fabrication process. The suggested connection is the welded bottom beam flange connection(M-2) and is compared with the existing PR-CC of bolted seat angle connection(M-1). Two specimens were fabricated in actual size and tested under monotonic loading. Based on the test results, the welded bottom beam flange connection exhibited about 85% of the stiffness of steel beam. It was similar to the bolted seat angle connection and behaved as PR-CC. The specimen of the supposed connection type failed at the shear connection of web but was similar to the bolted seat angle connection until the failure. It obtained sufficient stiffness and capacity through the reinforcingsteel and the capacity and deformational ability equivalent to the full-plastic moment through the anchor inside the steel tube at the web connection. So, it can be said that the suggested connection exhibits sufficient ductile behavior.

• Journal of Korean Society of Steel Construction
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• v.22 no.3
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• pp.271-280
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• 2010

This study was programmed to fabricate a beam-to-column connection that is limited to a steel-welded moment connection with full-scale members, using SN steel. A cyclic seismic test was conducted of the nine specimens that were fabricated by choosing the test variable for the weld access hole geometry, connection design method, and RBS. From the test results, failure modes, the moment-drift behavior, and the strain distribution were provided. From the specimen material properties, the beam's nominal plastic flexural capacity and classified qualified connection as a special moment flame were calculated. By analyzing the skeleton part and the baushinger part, a range of strength-raising effects, and deformation ratios were provided, with which the seismic performance of the specimens were evaluated. The test results showed that the specimens eliminated their weld access holes that demonstrated higher seismic performance than the specimens' existing weld access holes, and that the WUF-W connection that was reinforced by the supplemental fillet weld around the shear tap that was fastened by five bolts demonstrated superior seismic performance.