• Steel and Composite Structures
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• v.37 no.3
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• pp.323-339
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• 2020

In steel framed-tube structures (SFTSs), the plastic hinges at beam-ends cannot be adequately improved because of the large cross sections of spandrel beams, which results in the lower ductility and energy dissipation capacities of traditional SFTSs. To address this drawback, high-strength steel fabricated SFTSs with bolted web-connected replaceable shear links (HSFTS-SLs) have been proposed. In this system, shear links use conventional steel and are placed in the middle of the deep spandrel beams to act as energy dissipative components. In this study, 2/3-scaled HSFTS-SL specimens were fabricated, and cyclic loading tests were carried out to study the seismic performance of both specimens. The finite element models (FEMs) of the two specimens were established and the numerical results were compared with the test results. The results showed that the specimens had good ductility and energy dissipation capacities due to the reliable deformation capacities. The specimens presented the expected failure modes. Using a shorter shear link can provide a higher load-carrying capacity and initial elastic lateral stiffness but induces lower ductility and energy dissipation capacity in HSFTS-SLs. The performance of the specimens was comparable to that of the original sub-structure specimens after replacing shear links. Additionally, the expected post-earthquake recoverability and resilience of the structures could be achieved by replacing shear links. The acceptable residual interstory drift that allows for easy replacement of the bolted web-connected shear link was 0.23%. The bolted web-connected shear links had reliable hysteretic responses and deformation capacities. The connection rotation had a notable contribution to total link rotation. The results of the numerical analysis run for the proposed FEMs were consistent with the test results. It showed that the proposed FEMs could be used to investigate the seismic performance of the HSFTS-SL.

• Journal of the Korea Concrete Institute
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• v.23 no.5
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• pp.591-601
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• 2011

An experimental study was performed to evaluate the seismic performance of beam-column connections using 600 MPa re-bars for beam flexural reinforcement. Three full scale specimens of interior beam-column connection and two specimens of exterior beam-column connection were tested under cyclic loading. The specimens were designed to satisfy the requirements of Special Moment Frame according to current design code. The structural performance of the specimens with 600 MPa re-bar were compared with that of the specimen with 400 MPa re-bars. The test results showed that bond-slip increased in the beam-column joint. However, the load-carrying capacity, deformation capacity, and energy dissipation capacity of the specimens with 600 MPa re-bar were comparable to those of the specimens with 400 MPa re-bars.

• Journal of the Korean Geotechnical Society
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• v.15 no.1
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• pp.175-183
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• 1999

Recently, problems related to vibrations of decomposed granite soils have acquired increasing attention in Korea because those soils cover approximately one third of the country. Both resonant column and cyclic triaxial test were performed to investigate deformation characteristics of unsaturated and cement-mixed decomposed granite soils in Suwon region. The important soil parameters in this respect are the shear moduli, dynamic moduli of elasticity and damping ratios. The dynamic parameters are influenced by variables such as strain amplitude, ratio of loading cycles, and degree of saturations, etc. Test results and data have shown that the optimum degree of saturation to the maximum shear modulus due to a capillary menisci effect was about 17~18 % at low strain amplitude and 10~15 % at intermediate strain amplitude. This paper suggests the range of threshold strain and mean shear modulus of decomposed granite soils in Suwon region. It also proposed the empirical relationship between the dynamic parameters for cement-mixed and non-mixed decomposed granite soils.

• Transactions of the Korean Society of Automotive Engineers
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• v.24 no.2
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• pp.137-143
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• 2016

The fifth wheel coupler is a heavy automotive coupling structure which connects a tractor and a trailer used for heavy-duty trucks widely. It is subjected to various loads simultaneously such as rolling, pitching and yawing loads as well as coupling frictional and impact loadings. Most of existing couplers have been overdesigned and, therefore, it is necessary to reduce the dead weight to increase the fuel efficiency. The topology optimization was applied in order to find conceptual layout designs which could show major load paths and ribs locations, and then the size structural optimization was performed in order to determine the heights and thicknesses of coupler ribs with the predetermined various loading conditions for the development of a new slim coupler with a minimum weight and high enough strength and stiffness. As the results of the topology optimum design, an efficient new coupling structure for truck trailers was designed. The weight of the new fifth wheel coupler was reduced by 4.9 %, compared with the existing one, even though all strength requirements were satisfied. The fatigue test of the new coupler was performed with cyclic vertical loads (+78.4 to +235.2 kN) and horizontal loads (-91.2 to +91.2 kN) simultaneously at 1 Hz and the life of 2,000,000 cycles were achieved without failure.

• Journal of the Korean Geotechnical Society
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• v.16 no.3
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• pp.5-13
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• 2000

In this study, the Disturbed State Concept (DSC) constitutive model is calibrated and modified for steel-sand interface by using the HiS S model for relative intact (Rl) state and the critical state model for the fuBy adjusted (FA) part in the material. The general formulation for implementation is developed. Then, the DSC model with modification for interface is implemented in finite element program based on the generalized Biot's theory. The interface test under one-way monotonic and two-way cyclic loading were numerically simulated using the finite element program modified in this study. The DSC predictions show improved agreement with the observed results from laboratory test. Overall, the computer procedure with the DSC allows relatively improved simulation ofthe soil-structure interaction problems.oblems.

• Journal of Korean Society of Steel Construction
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• v.25 no.3
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• pp.255-265
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• 2013

The major goal of this study is to develop the industrialized structural system that can build high-rise buildings using the box-shaped steel frames such as a unit module system. In order to achieve such a goal, we need the advanced details for joints that consist in a single unit. Furthermore we also need to commercialize the unit modular building system through the basic experiments, research of theoretical analysis and the achievement of seismic performance. This study derived to develop the derails in the beam-to-column joint and to carry out structural performance test. Test results, a joint with thickness of 6.0T can be possible to maintain the plastic rotational angle for strength and seismic performance. Therefore, joint with thickness of 6.0T is able to apply when considering reinforcement in the local of stress concentration.

• Journal of the Korean Society for Nondestructive Testing
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• v.22 no.5
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• pp.516-522
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• 2002

For the experimental study of rotor steel, seven kind of specimens with different degradation levels were prepared by isothermal heat treatment at $630^{\circ}C$. Spherical indentation technique was developed to evaluate the flow properties of metallic materials in carbon steel, stainless steel, and alloys, etc. Through the spherical indentation test, differently degraded 1Cr-1Mo-0.25V steel's mechanical properties were observed and compared with conventional standard test data. The flow properties of 1Cr-1Mo-0.25V steel's were estimated by analyzing the indentation load-depth curve. To characterize the flow property, we used material yield slope and constraint factor index rather than strain-hardening exponent because the variation of strain-hardening exponent was very little and the data showed irregularly. And the constraint factor's effect was small when the material yield slope was taken into account.

• Journal of the Korea Concrete Institute
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• v.29 no.2
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• pp.201-208
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• 2017

In exterior beam-column joints, hooked bars are used for anchorage, but usage of high-strength and large-diameter bars increases, headed bar is preferred for solving steel congestion and difficulty in construction. To investigate the structural performance of headed bars, Six exterior beam-column joints were tested under cyclic loading. Tests parameter were the anchorage methods and concrete strength. The test results indicate that behavior of headed bar specimens shows similar performance with hooked bar specimens. All specimens failed by flexural failure of the beam. Headed bar specimens shows better performance in anchorage and joint shear. All specimens were satisfied the criteria of ACI374.1-05. Test results indicate that use of headed bar in exterior beam column joint is available.

• Steel and Composite Structures
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• v.26 no.6
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• pp.793-808
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• 2018

In this study, the seismic performance of the connections between L-shaped columns composed of concrete-filled steel tubes (L-CFST columns) and H-beams used in high-rise steel frame structures was investigated. Seven full-scale specimens were tested under quasi-static cyclic loading. The variables studied in the tests included the joint type, the axial compression ratio, the presence of concrete, the width-to-thickness ratio and the internal extension length of the side plates. The hysteretic response, strength degradation, stiffness degradation, ductility, plastic rotation capacity, energy dissipation capacity and the strain distribution were evaluated at different load cycles. The test results indicated that both the corner and exterior joint specimens failed due to local buckling and crack within the beam flange adjacent to the end of the side plates. However, the failure modes of the interior joint specimens primarily included local buckling and crack at the end plates and curved corners of the beam flange. A design method was proposed for the flexural capacity of the end plate connection in the interior joint. Good agreement was observed between the theoretical and test results of both the yield and ultimate flexural capacity of the end plate connection.

• Transactions of the Korean Society of Automotive Engineers
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• v.22 no.2
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• pp.141-147
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• 2014

This study aims to investigate the influence of bevel angles on the fatigue life of V-groove butt-welded joints with back-plates made by SM490A steel material, generally used for excavators, because changes in the geometry, material and surface properties of welded regions affect the fatigue life of welded structures. Butt type test specimens were prepared by the $CO_2$ welding of rolled steel plates (SM50A steel) with a thickness of 13.5 mm at a welding speed of 30 cm/min and these Butt type test specimens had two different groove angles, which are $40^{\circ}$ (A type) and $30^{\circ}$ (B type). In order to investigate differences in fatigue life between two types, 4-point bending fatigue tests were conducted with a stress ratio of R=0.1 under the cyclic loading environment at a frequency of 5 Hz at room temperature. The fatigue life of A type specimens was approximately 7% higher than that of B type specimens. The stress concentration factors calculated by finite element analysis were 2.16 for A type and 2.25 for B type, whose difference was caused by the influence of the back-plates of butt-welded structures. The current results could provide important guidelines to determine the V-groove angle of butt-welded joints with a satisfactory fatigue life, although under severe operating conditions.