• Proceedings of the Computational Structural Engineering Institute Conference
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• 1992.04a
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• pp.65-70
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• 1992

This study deals with the finite element analysis of the monotonic behavior of reinforced concrete beams and beam-column joint subassemblages. It is assumed that the behavior of these members can be discribed by a plane stress field. Concrete and reinforcing steel are represented by separate material models which are combined together with a model of the interaction between reinforcing bar and concrete through bond-slip to discribe the behavior of the composite reinforced concrete material. To discribe the concrete behavior, a nonlinear orthotropic model is adopted and the crack is discribed by a system of orthogonal cracks, which are rotating as the principal strain directions are changed. A smeared finite element model based on the fracture mechanics principles are used to overcome the numerical defect according to the finite element mesh size. Finally, correlation studies between analytical and experimental results and several parameter studies are conducted with the objective to estabilish the validity of the proposed model and identify the significance of various effects on the local and global response of reinforced concrete members.

• Composites Research
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• v.33 no.6
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• pp.360-364
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• 2020

Although research and development of existing steel-made Cowl Cross Member(CCM) was carried out with magnesium and plastic to make vehicles lighter, it is difficult to apply them to performance problems in the vehicle's mounting condition. Recently, the company is conducting research on the injection CCM of the composite insert as a lightweight component that is most suitable for mass-production of automotive parts. This is a manufacturing process that inserts composite injection bracket parts into aluminum bar, and the adhesion of the two parts is one of the important factors considering the vehicle's mounting conditions. In this study, the joint strength of Aluminum bar is one of the important factors as a study for the injection of aluminum bar into PA6-GF60 composite material. For the analysis of these research, the method of spraying adhesive to the aluminum bar and the case of knurling treatment have been analyzed and the bonding strength of the direction of rotation and lateral direction has been analyzed for each part between the aluminum bar of the cowl cross member and the shape of the injection component of composite materials.

• Journal of Korean Society of Steel Construction
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• v.23 no.3
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• pp.377-384
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• 2011

Recently, for the purpose of reducing work terms and improving performance for construction work, various methods in structure field were developed. This included the HRC system which is applicable to a typical structure (e.g., parking and office building). The HRC system introduced the Gerber Joint to raise structural efficiency and used connection plate to bolt HRC composite beam to H beam in the construction field. In this research, the experimental tests for six specimens, which were in the same field conditions, were conducted with several parameters such as the length and height of the connection plate and the number of stub bolts. The test result was compared with those made by current design codes for the deflection and strains of the main bar. Within the given load, the integration of concrete in beam and connection plate, welded with stud bolts, was verified.

• Structural Engineering and Mechanics
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• v.87 no.2
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• pp.137-149
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• 2023

In this study, to explore the working performance of the CFST split spherical node wind power tower, two groups of CFST split spherical joint plane towers with different web wall thicknesses and a set of space systems were analyzed. The tower was subjected to a low-cycle repeated load test, and the hysteresis and skeleton curves were analyzed. ABAQUS finite element simulation was used for verification and comparison, and on this basis parameter expansion analysis was carried out. The results show that the failure mode of the wind power tower was divided into weld tear damage between belly bar, high strength bolt thread damage and belly rod flexion damage. In addition, increasing the wall thickness of the web member could render the hysteresis curve fuller. Finally, the bearing capacity of the separated spherical node wind power tower was high, but its plastic deformation ability was poor. The ultimate bearing capacity and ductility coefficient of the simulated specimens are positively correlated with web diameter ratio and web column stiffness ratio. When the diameter ratio of the web member was greater than 0.13, or the stiffness ratio γ of the web member to the column was greater than 0.022, the increase of the ultimate bearing capacity and ductility coefficient decreased significantly. In order to maximize the overall mechanical performance of the tower and improve its economy, it was suggested that the diameter ratio of the ventral rod be 0.11-0.13, while the stiffness ratio γ should be 0.02-0.022.

• Journal of Korean Society of Steel Construction
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• v.16 no.6 s.73
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• pp.769-780
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• 2004

This paper's objective is to evaluate the experimental behavior of gap N-joints made of cold-formed, square, hollow steel sections, with a connection plate as a tension member. The principal parameters for testing included the ratio of chord width to thickness, the ratio of brace width to chord width, eccentric ratio, the shape of the compression member, the branch angle, and the stiffening plate of the chord flange. The strength and failure mode were examined through the test for the gap N-joint, consisting of several parameters. Based on the results of the test, the gap N-joints were determined according to the capacity preceding the displacement of the tension, regardless of the width ratio, and the split failure mode-connected surface for a chord in joints. The strength of the gap N-joints increased proportionally as the $2\gamma$(B/T) ratio decreased, and as the width ratio(${\beta}$) of branch to chord increased. Particularly, $2\gamma$(B/T) decreased as the capacity of gap N-joint increased. The results of the test were summarized for the capacity, initial stiffness, ductility, and change of the failure mode of each gap N-joint.

• Journal of the Korea institute for structural maintenance and inspection
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• v.27 no.6
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• pp.94-101
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• 2023

In this study, the development performance of the head bars, which is SD700, was experimentally evaluated at the RC (reinforced concrete) or SFRC (steel fiber reinforced concrete external beam-column joint. A total of 10 specimens were tested, and variables such as steel fibers, length of settlement, effective depth of the beam, and stirrups of the column were planned. As a result of the experiment, the specimens showed side-face blowout, concrete breakout, and shear failure depending on the experimental variables. In the RC series experiments with development length as a variable, it was confirmed that the development strength increased by 26.5~42.2% as the development length increased by 25-80%, which was not proportional to the development length. JD-based experiments with twice the effective depth of beams showed concrete breakout failure, reducing the maximum strength by 31.5% to 62% compared to the reference experiment. The S-series experiment, in which the spacing of the shear reinforcement around the enlarged head reinforcement was 1/2 times that of the reference experiment, increased the maximum strength by 8.4 to 9.7%. The concrete compressive strength of SFRC was evaluated to be 29.3% smaller than the concrete compressive strength of RC, but the development strength of SFRC specimens increased by 7.3% to 12.2%. Accordingly it was confirmed that the development performance of the head bar was greatly improved by reinforcing the steel fiber. Considering the results of 92% and 99% of the experimental maximum strength of the experiment arranged with 92% and 110% of the KDS-based settlement length, it is judged that the safety rate needs to be considered even more. In addition, it is required to present a design formula that considers the effective depth of the beam compared to the development length.

• Journal of Welding and Joining
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• v.9 no.1
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• pp.40-47
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• 1991

The most fatigue tests carried out under the either stress or strain control, but machines and structures had taken variable stress. This variable stress was treated as statistics based on p-type distributions. In this paper, the cumulative fatigue damage of SM45C round bar specimens having a center hole resulting from block loading with p-distributions in rotating bending conditions, is presented. The value of p was changed in the range from 0.25 to 1; 0.25, 0.5, 0.75, 1. The following conclusions were obtained through the constant stress amplitude experiments and the block loading experiments. (1) In constant loading test, fatigue life was affected by cyclic rate. From experimental data, N$_{f}$ (100cpm)/N$_{f}$(3000cpm)equal to 0.56. (2) In case of the cyclic rate 100cpm and 3000cpm, at the high stress amplitude level the crack propagation life N$_{*}$f is longer than the low stress amplitude level. (3) Miner's hypothesis may be valid for p=0.75 and prediction of fatigue life by Haibach's method agree with experimental data well for the case p=0.5, while the modified Miner's method agree with experimental data well for the case p=0.25.5.

• Magazine of the Korea Concrete Institute
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• v.6 no.3
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• pp.152-161
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• 1994

Most widened bridges have been constructed by the joining-construction method that makes new and existing bridges structurally a single structure. Since the joining-construction method has several problems in design and construction viewpoint, this study is conducted in order to investigate the structural behaviors of RC slabs, which are widened and influenced by traffic-induced vibration of existing bridge during placing and curing of new concrete, with the prototype flexural strength test and FEM analysis. It was found that cracks are generated in construction joint at low applied load and that stress concentration at the joints and slips between steel bar and concrete are occured. But, the decreasing of load carrying capacity is negligible according to the traffic-induced vibration as well as the difference of construction method.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.1
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• pp.85-90
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• 2010

Friction welding is a common practice to join axially symmetrical parts for automobile industry applications. The shaft for automobile reverse idle gear is generally produced by forging steel, SF 45. This method is not so good because of high cost of material and production. In this study, in order to investigate the possibility of application of SM 45C to SF 45 dissimilar friction welding, the dissimilar friction welded joints were performed using 20 mm diameter solid bar in forging steel(SF 45) to carbon steel(SM 45C). The optimal friction welding parameters were selected to ensure reliable quality welds on the basis of visual examination, tensile test, micro-Virkers hardness surveys of the bond of area and optical microstructure investigations for welded joint parts. Finally, post weld heat treatment(PWHT) of the high-frequency induction hardening was performed for the friction welded specimens under the optimal welding conditions. And then, the mechanical properties were compared for as-welded and PWHT in SM 45C to SF 45.

• Journal of the Korea institute for structural maintenance and inspection
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• v.26 no.1
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• pp.73-80
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• 2022

In this study, details of NRC beam-column connections were developed in which beam and columns pre-assembled in factories using steel angles were bolted on site. The developed joint details are NRC-J type and NRC-JD type. NRC-J type is a method of tensile joining with TS bolts to the side and lower surfaces of the side plate of the NRC column and the end plate of the NRC beam. NRC-JD type has a rigid joint with high-strength bolts between the NRC beam and the side of the NRC column for shear, and with lap splices of reinforcing bar penetrating the joint and the beam main reinforcement for bending. For the seismic performance evaluation of the joint, three specimens were tested: an NRC-J specimen and NRC-JD specimen with NRC beam-column joint details, and an RC-J specimen with RC beam-column joint detail. As a result of the repeated lateral load test, the final failure mode of all specimens was the bending fracture of the beam at the beam-column interface. Compared to the RC-J specimen, the maximum strength of the specimen by the positive force was 10.1% and 29.6% higher in the NRC-J specimen and the NRC-JD specimen, respectively. Both NRC joint details were evaluated to secure ductility of 0.03 rad or more, the minimum total inter-story displacement angle required for the composite intermediate moment frame according to the KDS standard (KDS 41 31 00). At the slope by relative storey displacemet of 5.7%, the NRC-J specimen and the NRC-JD specimen had about 34.8% and 61.1% greater cumulative energy dissipation capacity than the RC specimen. The experimental strength of the NRC beam-column connection was evaluated to be 30% to 53% greater than the theoretical strength according to the KDS standard formula, and the standard formula evaluated the joint performance as a safety side.