• Proceedings of the KSR Conference
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• 2008.06a
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• pp.2200-2206
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• 2008

This paper describes the results of experiments on the bending behavior of welded square tube structures for drive shaft sub frame of BIMODAL Tram. The used specimens to test were two different type made of ATOS60 and ST52-3. The square tube made of ST52-3 is the non-welded structure, while the square tube made of ATOS60 is the welded structure. The welded square tube made of ATOS60 will be applied for drive shaft sub frame of BIMODAL Tram. This welded square tube could reduce the manufacturing cost in comparison of non-welded square tube. The results showed that the bending performance of welded square tube made of ATOS60 was proven, and the bending behavior was in an good agreement with that of nonlinear finite element analysis.

• Proceedings of the KSME Conference
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• 2001.06a
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• pp.812-818
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• 2001

The drop type impact test and finite element analysis are established for examining the buckling behavior of a square tube under the lateral impact load. Based on these results, the effects by the boundary conditions for supporting the structure are reviewed, which are as follows. One is pinned condition by screw; the other is fixed by welding. The critical impact force and acceleration by test are nearly same between two cases. However, the critical impact velocity of the pinned condition is higher than that of the fixed case. Therefore, the dynamic buckling behavior of a pinned structure is better than the fixed condition in view of critical impact velocity. These test and analysis results will be adaptable for predicting the dynamic structural integrity of a tube structure not only the axial impact event but the lateral impact event.

• Steel and Composite Structures
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• v.14 no.2
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• pp.133-153
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• 2013

The concrete-filled steel tube (CFT) columns have several benefits of high load-bearing capacity, inherent ductility and toughness because of the confinement effect of the steel tube on concrete and the restraining effect of the concrete on local buckling of steel tube. However, the experimental research into the behavior of square CFT columns consisting of high-strength steel and high-strength concrete is limited. Six full scale CFT specimens were tested under flexural moment. The CFT columns consisted of high-strength steel tubes ($f_y$ = 325 MPa, 555 MPa, 900 MPa) and high-strength concrete ($f_{ck}$ = 80 MPa and 120 MPa). The ultimate capacity of high strength square CFT columns was compared with AISC-LRFD design code. Also, this study was focused on investigating the effect of high-strength materials on the structural behavior and the mathematical models of the steel tube and concrete. Nonlinear fiber element analyses were conducted based on the material model considering the cyclic bending behavior of high-strength CFT members. The results obtained from the numerical analyses were compared with the experimental results. It was found that the numerical analysis results agree well with the experimental results.

• Proceedings of the Korean Society For Composite Materials Conference
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• 1999.11a
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• pp.168-171
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• 1999

For the axial crushing tests of various shape of tubes, it was reported that composite tubes need trigger mechanism to avoid brittle failure. In this study, static axial crush tests were performed with the new aluminum/GFRP hybrid tubes. Glass/Epoxy prepregs were wrapped around aluminum tube and co-cured. The failure of hybrid tube was stable and progressive without trigger mechanism, and specific energy absorption was increased to maximum 34% in comparison with aluminum tube. Effective energy absorption is possible for inner aluminum tube because wrapped composite tube constrain the deflection of aluminum tube and reduce the folding length. The failure of hybrid composite tube was stable without trigger mechanism because inner aluminum tube could play the role of crack initiator and controller. Aluminum/Glass-Epoxy hybrid tube is suitable for the vehicle front structure due to effective energy absorption capability, easy production, and simple application for RTM process.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2000.11a
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• pp.84-87
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• 2000

Square tubes used for vehicle structure components have an important role on keeping its stiffness and preserving occupant safety in vehicle collision and rollover in which it experience axial collapse, bending collapse or both. Bending collapse, which absorbs kinetic energy of the impact and retains a survival space for the occupant, is a dominant failure mode in oblique collision and rollover. Thus, in this paper, the bending collapse characteristics such as the maximum bending moment and energy absorption capacity of the square tube replaced by light-weight material were evaluated and presented. The bending test of cantilever tubes which were fabricated with aluminum, GFRP and aluminum/ GFRP hybrid by co-curing process was performed. Then the maximum bending moment and the energy absorption capacity from the moment-angle curve were evaluated. Based on the test results, it was found that aluminum/ GFRP hybrid tube can show better specific energy absorption capacity compared to the pure aluminum or GFRP tube and can convert unstable collapse mode which may occur in pure GFRP tube to stable collapse mode like a aluminum tube in which plastic hinge is developed.

• Steel and Composite Structures
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• v.20 no.3
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• pp.487-500
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• 2016

In order to investigate the flexural bearing capacity of panel zone of diaphragm-through joint between concrete filled square steel tubular column and steel beam, four specimens were tested under static tension loads to study the mechanical properties and bearing capacity of diaphragm-through joints with a failure mode of panel zone. Finite element models of these specimens were developed to simulate the test and compare the predicted failure modes, load-displacement curves and bearing capacities with the experimentally observed. It was found that the tensile load from the steel beam flange is mainly shared by the square steel tube and the diaphragm. The diaphragm plastic zone appears along the cross-section lines enclosed by the square steel tube and the influence of steel beam web on the plastic zone of the steel tube is significant and cannot be neglected. Computational models of yield lines on square steel tube and diaphragm are established based on the distribution pattern of the plastic zone, and an analytical method for the evaluation of the bearing capacity of the joint is proposed. The theoretical results and the experimental data are compared and found in good agreement.

• Steel and Composite Structures
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• v.10 no.3
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• pp.261-279
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• 2010

Generally, a box tube, which is used for an existing square CFT structure, is made by welding four plates. The manufacturing efficiency of this steel tube is poor, and it also needs special welding technology to weld its internal diaphragm and the through diaphragm. Therefore, an interior-anchor-type square steel tube was developed using the method of cold-forming thin plates to prevent welding of the stress concentration position, and to maximize the section efficiency. And, considering of the flow of beam flange load, the efficiency of erection and the weldability of the diaphragm to thin walled steel column, the external diaphragm connection was selected as the suitable type for the welded built-up square CFT column to beam connection. And, an analytical study and tests were conducted to evaluate the structural performance of the suggested connection details and to verify the suggested equations for the connection details. Through this study, the composite effect of the internal anchor to concrete, the resistance and stress distribution of the connections before and after the existing column is welded to the beam, the effective location of welding in connection were analyzed.

• Journal of Korean Society of Steel Construction
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• v.12 no.2 s.45
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• pp.209-219
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• 2000

Concrete Filled steel Tube(CFT) Column has an excellent structural capacities in accordance with an interaction effect between the steel tube and concrete. Recently, CFT structure has been focussed on a structural system for a high-rise buildings. The purpose of this study is to evaluate a strength and deformation capacity of CFT square columns subjected to constant axial and cyclic lateral load. The test parameters are diameters to thickness ratio of steel tube, axial load ratios, concrete strengths, load applying types and whether or not filled concrete. Total sixteen specimens are fabricated to clarify the energy absorbtion capacity of CFT columns. Experimental results are summarized for maximum strength, initial stiffness and deformation capacity.

• Steel and Composite Structures
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• v.22 no.1
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• pp.63-77
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• 2016

Top-down construction is a construction technique in which pit excavation and structure construction are conducted simultaneously. Reducing construction time and minimizing noise and vibration which affect neighboring structures, the technique is widely employed in constructing downtown structures. While H-steel columns have been commonly used as core columns, concrete filled steel tube (CFT) columns are at the center of attention because the latter have less axial directionality and greater cross-sectional efficiency than the former. When compared with circular CFT columns, square CFT columns are more easily connected to the floor structure and the area of percussion rotary drilling (PRD) is smaller. For this reason, square CFT columns are used as core columns of concrete encased and filled square (CET) columns in underground floors. However, studies on the structural behavior and concrete stress transfer of CET columns have not been conducted. Since concrete is cast according to construction sequence, checking the stress of concrete inside the core columns and the stress of covering concrete is essential. This paper presents the results of structural tests and analyses conducted to evaluate the usability and safety of CET columns in top-down construction where CFT columns are used as core columns. Parameters in the tests are loading condition, concrete strength and covering depth. The compressive load capacity and failure behavior of specimens are evaluated. In addition, 2 cases of field application of CET columns in underground floors are analyzed.

• Journal of Korean Society of Steel Construction
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• v.25 no.4
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• pp.347-357
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• 2013

Recently, In recognition of outstanding structural performance the use of Concrete Filled steel Tube(CFT) columns has been increased. Research is ongoing that effective use of cross-sectional because steel strength development and rising prices. In this Lab, suggests new shape by Thin steel plates bent to be L-channel welded to form square steel tube to maximize efficiency of the cross section. In addition, since the rib placed at the center of the tube width acts as an anchor; higher load capacity of buckling is acceptable. we have developed New shape welded built-up square tube for broader usability which were bent to be L-shaped and thin Plate each unit member were welded. In order to apply the new shape built-up square columns, we predicted structure behavior, stress distribution with parameter Width thickness ratio. The experimental results presented in standards and even exceed the b/t of the rib anchors installed in the role due to exert enough strength and deformation to improve performance was favorable.