• Journal of the Korea Concrete Institute
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• v.16 no.2 s.80
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• pp.163-174
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• 2004

A number of experiments were performed to investigate the punching shear strength of flat plate-column connections. According to the experiments, the punching shear strength varies significantly with design parameters such as the column size of the connection, reinforcement ratio, and boundary condition. However, current design methods do not properly address the effects of such design parameters. In the present study, a theoratical approach using Rankine's failure cirterion was attempted to define the failure mechanism of the punching shear According to the study, the failure mechanism can be classified into the compression-controlled and the tension-controlled, depending on the amount of bottom re-bars placed at the connection, and the punching shear strength is also significantly affected by the flexural damage of slab. Based on the finding, a new strength model of punching shear was developed, and verified by the comparisons with existing experiments and nonlinear finite element analyses. The comparisons show that the proposed strength model addressing the effects of various design parameters can predict accurately the punching shear strength, compared to the existing strength models.

• Journal of the Earthquake Engineering Society of Korea
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• v.10 no.4 s.50
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• pp.67-76
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• 2006

In this paper the moment transfer efficiency of a web and the strain concentration at the RHS (Rectangular Hollow Section) column-to-steel beam connections was evaluated. Initially, non-linear finite element analysis of five bare steel beam models was conducted. The models were designed to have different detail at their beam-to-column connection, so that the flexural moment capacity was different respectively. Analysis results showed that the moment transfer efficiency of the analytical model with RHS-column was poor when comparing to model with WF(Wide Flnage)-column due to out-of-plane deformation of the RHS-column flange. The presence of scallop and thin plate of RHS column was also a reason of the decrease of moment transfer efficiency, which would result in a potential fracture of the steel beam-to-column connections. Analytical results were compared with the previous experimental results. The analytical and the previous experimental results showed that the strain concentration was inversely proportional to the moment transfer efficiency of a beam web and the deformation capacity of connection was poor as their moment transfer efficiency degrades. Further finite element analyses of composite beam with a floor slab revealed that the neutral axis moved toward the top flange and the moment transfer efficiency of a beam web decreased, which led to premature failure of the connection.

• Journal of Korean Society of Steel Construction
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• v.16 no.2 s.69
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• pp.247-255
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• 2004

An experimental program was undertaken to develop seismic retrofit methods of existing steel moment connections with floor slab for improved seismic performance. Five full-scale composite specimens were tested under cyclic loading. Conventional through-diaphragm connections [please check this; no search results were found for through-diaphragm connections] composed of square-tube column and H-beam were retrofitted by adding either a bottom-flange dogbone (RBS) or an improved welded horizontal stiffener at the beam bottom flange. The effectiveness of the proposed retrofit connections schemes was evaluated. The specimen retrofitted using the RBS concept at the bottom flange showed poor connection ductility. In contrast. specimens with the proposed horizontal stiffener details exhibited improved connection ductility.

• Journal of the Korea Concrete Institute
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• v.18 no.3 s.93
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• pp.405-414
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• 2006

In the present study, a numerical analysis was performed for interior connections of continuous flat plate to analyze the effect of design parameters such as column section shape, gravity load and slab span on the behavioral characteristics of the connections. For the purpose, a computer program for nonlinear FE analysis was developed, and the validity was verified. Through the parametric study, the variations of shear stress distribution around the connection were investigated. According to the result of numerical analysis, as the length of the cross section of column in the direction of lateral load increases and gravity load increases, the effective area and the maximum shear strength providing the torsional resistance decrease considerably. And as the slab span loaded with relatively large gravity load increases, the negative moment around the connection increases and therefore the strength of connection against unbalanced moment decreases. By considering the effect of design parameters on the strength of the connections, the effective shear strength to calculate the torsional moment capacity of connection was proposed and the effectiveness of the proposed shear strength was verified.

• Journal of Korean Tunnelling and Underground Space Association
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• v.14 no.6
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• pp.653-666
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• 2012

This study made progress about Demage Mechanism of Transition Section in Cut and Cover Tunnel. For this study, Inspection and test was carried out about Transition Section. After this process, Numerical Analysis was accomplished by 2D, 3D. A result of inspection and test, It couldn't find the reason why the upper slab Demage was detected. So 2D Numerical Analysis was conducted. It was analyzed that the Safety Factor(1.0) was satisfied in 2D. But, the result of 3D Numerical Analysis, The reason was found that the Demage on upper slab was caused by moment change. The Moment was changed by column interval transition. For Retrofitting, Column was added under slab in tunnel. It was found that the addition column decreased upper slab deformation. After this study, It could be find that are important 3D Numerical Analysis as well as 2D Numerical Analysis in case of Transition Section. This Study can help developing construction and maintenance about Tunnel. Finally, It's going to study Retrofitting plans which have minimum influence of Transition Section in Cut and Cover Tunnel.

• Journal of the Society of Disaster Information
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• v.15 no.3
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• pp.418-426
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• 2019

Purpose: After analyzing the seismic capability of low-rise RC grid structures with insufficient seismic performance, the purpose of the project is to install steel slab hysteretic dampers (SSHD) to improve the seismic performance of beams and columns, and to suggest measures to minimize damage to the structure and human damage when an earthquake occurs. Method: The evaluation of the seismic performance of a structure is reviewed based on the assumption that the seismic performance is identified for the grid-type subway systems that are not designed to be seismic resistant and the installation of an SSHD system, a method that minimizes construction period, if insufficient, is required. Result: After the application and reinforce of structure with SSHD, and the results of eigenvalue analysis are as follows. The natural periodicity of longitudinal direction was 0.55s and that of vertical direction was 0.58s. Conclusion: As results of cyclic load test of structure with SSHD, the shear rigidity of damper is 101%, the energy dissipation rate is 108% and, plastic rotation angle of all column and beam is satisfied for $I_o$ level and therefore it is judged that the reinforce effect is sufficient.

• Journal of Korean Society of Steel Construction
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• v.20 no.4
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• pp.529-537
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• 2008

The objective of this paper is to propose retrofit design methods of theRHS column-to-H beam connections with floor slabs. Referring to previous studies on the retrofitting of moment connections, it is clear that connections retrofitted with a stiffened RBS (SR) or a lengthened horizontal stiffener (LH) has an effect on decreasing the stress/strain concentration. A new design procedure using these two retrofitting methods was thus presented. In addition, this paper addressed various design or detailing options and recommended a procedure for designing the improved retrofitting method of steel moment connections. Finally, a pilot test was conducted to verify the design procedure.

• Journal of the Korea Concrete Institute
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• v.18 no.5 s.95
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• pp.595-602
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• 2006

An experimental study was conducted to investigate seismic behaviour of post-tensioned(PT) exterior slab-column connections used for the purpose to resist gravity loads only. For these, 2/3-scale, two PT post-tensioned exterior connections with two different tendon arrangement patterns and one conventional reinforced concrete(RC) exterior connection was tested under quasi-static, uni-directional reversed cyclic loading. During the lateral testing, gravity forces transferred to the column were kept constant to closely simulate a moment to shear ratio of a real building. One of the objectives of this study was to assess the necessity and/or the quantity of bottom bonded reinforcement needed to resist moment reversal which would occur under significant inelastic deformations of the adjacent lateral force resisting systems. The ACI 318 and 352 provisions for structural integrity were applied to provide the bottom reinforcement passing through the column for the specimens. Prior test results were also collected to conduct comparative studies for some design parameters such as the tendon arrangement pattern, the effect of post-tensioning forces and the use of bottom bonded reinforcement. Consequently, the impact of tendon arrangement on the seismic performance of the PT connection, that is lateral drift capacity and ductility, dissipated energy and failure mechanism, was considerable. Moreover, test results showed that the amount of bottom reinforcement specified by ACI 352. 1R-89 was sufficient for resisting positive moments arising from moment reversal under reversed cyclic loads. Shear strength of the tested specimens was more accurately predicted by the shear strength equation(ACI 318) considering the average compressive stress over the concrete($f_{pc}$) due to post-tensioning forces than that without considering $f_{pc}$.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.22 no.1
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• pp.25-34
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• 2009

RC flat plate, which has no large flexural stiffness by boundary beams, may be governed by serviceability as well as strength condition. A construction sequence and its impact on distributions of construction loads among slabs tied by shores are decisive factors on immediate and long term performances of flat plate. The over-loading and tensile cracking in early-aged slabs significantly increase the deflection of flat plate system. In this study, for slab deflections, the practical analysis scheme using a linear analysis program is formulated with considering construction sequence and concrete cracking effects. The concept of the effective moment of inertia in calculating deflections of one-way bending member, that is presented in structural design codes, is extended to the finite element analysis of the two-way slab system of flat plates. Effects of over-loads during construction on deflections of flat plate system are analyzed by applying the proposed practical analysis scheme into the critical construction load conditions calculated from the simplified method.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.5 no.1
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• pp.1-12
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• 1985

This study is conserned for the optimum design of reinforced concrete slab-beam-column structures with multi-storys and multi-bays by Direct Method. Flexural and shear strength, sectional size, and steel ratio etc., were considered as the design-constraints and the cost function was taken as to objective function. They became high degree nonlinear problems. Using SLP as an analytical method of nonlinear optimal problems, an optimal algorithm was developed in this study and the algorithm was applied to the optimization of reinforced concrete structure system of 5 storys. The result converged to a optimal solution with 3 to 5 iterations, and proved that economical design could be possible when compared with conventional designs.