• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.241-244
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• 2008

In general, RC flat plate frames have been used as a gravity load resisting system(GLRS) in building. This system should be constructed with lateral force resisting system(LFRS) such as shear walls and brace frames. When lateral loads such as earthquakes occur, LFRS undergo displacement by which connected gravity systems experience lateral displacement. Thus, flat plate system designed as GLRS should be predict unbalanced moments and punching failure due to lateral deformation. This study developed an analytical mode for predicting nonlinear behavior of RC slab column connection for the seismic performance evaluation of RC flat plate frames. For verifying the analytical model, the test results of two flat plate specimens having two continous spans with the difference gravity shear ratio($V_g/{\phi}V_c$) were compared with the results of analysis. The developed model can predict the failure modes and punching failures.

• Journal of the Earthquake Engineering Society of Korea
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• v.11 no.6
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• pp.53-61
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• 2007

This study investigates the effect of site class, post-yield stiffness ratio, damping ratio, yield-strength reduction factor, and natural period on inelastic displacement ratio of bilinear SDF systems located at the sites classified as NEHRP site class B,C,D. The previous studies developed inelastic displacement ratio using equal displacement rule in the intermediate and long period range. But, this approximation overestimates the inelastic displacement ratio. Furthermore, inelastic displacement ratio has not been developed for the systems having a damping ratio less than 5%. This study conducts nonlinear regression analysis for proposing equations for calculating median and deviation of the inelastic displacement ratio of the bilinear SDOF system having damping ratios ranging from 0 to 20%. Using median and deviation of the inelastic displacement ratio, probabilistic inelastic displacement ratio is estimated, which can be used for performance-based seismic evaluation.

• Journal of the Earthquake Engineering Society of Korea
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• v.12 no.3
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• pp.21-28
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• 2008

To evaluate the seismic performance of multi-degree of freedom(MDF) systems, repeated nonlinear response history analyses are often conducted, which require extensive computational efforts. To reduce the amount of computation required, equivalent single degree of freedom(SDF) systems representing complex multi-degree of freedom(MDF) systems have been developed. For the equivalent SDF systems, bilinear models and trilinear models have been most commonly used. In these models, the P-$\Delta$ effect due to gravity loads during earthquakes can be accounted for by assigning negative stiffness after elastic range. This study evaluates the adequacy of equivalent SDF systems having these hysteretic models to predict the actual response of steel moment resisting frames(SMRF). For this purpose, this study conducts cyclic pushover analysis, nonlinear time history analysis and incremental dynamic analysis(IDA) for SAC-Los Angeles 9-story buildings using nonlinear MDF models(exact) and equivalent SDF models(approximate). In addition, this study considers the strength limited model.

• Structural Engineering and Mechanics
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• v.75 no.6
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• pp.675-684
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• 2020

An innovative retrofit method using pre-stressed steel strips and externally-bonded steel plates was presented in this paper. With the aim of exploring the seismic performance of the retrofitted RC interior joints, four 1/2-scale retrofitted joint specimens together with one control specimen were designed and subjected to constant axial compression and cyclic loading, with the main test parameters being the volume of steel strips and the existence of externally-bonded steel plates. The damage mechanism, force-displacement hysteretic response, force-displacement envelop curve, energy dissipation and displacement ductility ratio were analyzed to investigate the cyclic behavior of the retrofitted joints. The test results indicated that all the test specimens suffered a typical shear failure at the joint core, and the application of externally-bonded steel plates and that of pre-stressed steel strips could effectively increase the lateral capacity and deformability of the deficient RC interior joints, respectively. The best cyclic behavior could be found in the deficient RC interior joint retrofitted using both externally-bonded steel plates and pre-stressed steel strips due to the increased lateral capacity, displacement ductility and energy dissipation. Finally, based on the test results and the softened strut and tie model, a theoretical model for determining the shear capacity of the retrofitted specimens was proposed and validated.

• The Journal of the Convergence on Culture Technology
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• v.6 no.4
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• pp.753-760
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• 2020

In this study, the structural safety of the bearing support was analysed by applying the vertical load (bearing design load) and horizontal load (horizontal force generated during an earthquake) using a precise three-dimensional numerical model. The results of stress and displacement of newly-poured concrete and welded rebars were confirmed numerically. Numerical results show that the increase in the horizontal force and the height of the beam causes the concrete cracking and the stress increase of the rebar connections due to the increase of the stress at the new concrete interface. Therefore, it was analyzed that the increase in the height of bearing support is directly related to the horizontal force and it is necessary to apply the bearing support height appropriate for the bearing support capacity. It was proposed that a method of setting the height of the bearing support suitable for the bearing capacity and determining the reinforcement by presenting the guideline with the correlation between the horizontal force acting on the bearing support and its height.

• Journal of the Earthquake Engineering Society of Korea
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• v.15 no.1
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• pp.39-48
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• 2011

In this present study, a response modification factor for a lightweight steel panel-modular system which is not clarified in a current building code was proposed. As a component of the response modification factor, an over-strength factor and a ductility factor were drawn from the nonlinear static analysis curves of the systems modeled on the basis of the performance tests. The final response modification factor was then computed by modifying the previous response modification factor with a MDOF (Multi-Degree-Of-Freedom) base shear modification factor considering the MDOF dynamic behaviors. As a result of computation for the structures designed as a dual frame system, ranging from 2-story to 5-story, the value of 4 was estimated as a final response modification factor for a seismic design, considering the value of 5 as an upper limit of the number of stories.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.20 no.6
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• pp.761-767
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• 2007

In centralized control system, complicated control systems including sensors, power supply and dampers should be required to satisfy the target response of large-scale structures. The practical applications of the centralized control system, however, is very difficult due to high order finite element model of structures, uncertainty of models, and limitations of the excitation system. In this study, the decentralized response-dependent MR damper of which magnetic field is automatically modulated according to the displacement or velocity transferred to the damper without any sensing and computing systems. this decentralized response-dependent MR damper are investigated according to the ranges of relative magnitude between the control force of MR damper and the story shear force of structures by nonlinear time history analysis. Finally, its performance is compared with centralized LQR algorithm which is used in general centralized control theory for a three story building structure.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.1
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• pp.284-289
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• 2016

In recent years, the earthquake sequence in Christchurch, New Zealand (NZ) was unprecedented in terms of repeated earthquake shocks with substantial levels of ground motion affecting modern infrastructure, and in particular, broad and precise reports for liquefaction-induced permanent ground deformation (PGD) and repairs of wastewater (WW) pipelines were collected. In this study, a geographical information system (GIS) and linear regression analysis were performed using data for the length and repair points of earthenware (EW) and concrete (CONC) wastewater pipelines acquired after the MW 6.2 February 22, 2011 earthquake. The repair rates (repairs/km) for the EW and CONC wastewater pipelines were evaluated inside the areas of PGD, and both angular distortion of ground and lateral ground strain were calculated from the high resolution LiDAR data acquired before and after the seismic event. The research results showed that both pipelines have similar trends of damage but the CONC wastewater pipeline with higher stiffness showed less damage. The results of linear regression analyses can be used to predict the repair rates for EW and CONC wastewater pipelines inside the areas of PGD induced by future earthquakes.

• Journal of Korean Society of Steel Construction
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• v.17 no.4 s.77
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• pp.459-467
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• 2005

This study focuses on the development of a new method of H-shaped beam-to-square column connection with an outer diaphragm and a field welding. The specific type of beam-to-column connection with an external stiffener, using field welding, is proposed. The structural behavior of this connection was examined experimentally. Two loading type tests were conducted under the experimental parameters given as details. First described was the symmetrical loading test, which supported both ends or a beam simply and applied a load from the column to the pend (What does this mean?) to investigate a fundamental characteristic of this connection. Further described was the anti-symmetrical loading test, which carried out simple support of the column'stop end and the column base, and applied a load from both ends of a beam to investigate the structural performance of this connection. From the results, it is clear that the external- stiffener-type connection proposed in this paper is the reliable connection method.

• Steel and Composite Structures
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• v.10 no.2
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• pp.187-205
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• 2010

The existing CFT columns present the deterioration in confining effect after the yield of steel tube, local buckling and the deterioration in load capacity. If lateral load such as earthquake load is applied to CFT columns, strong shearing force and moment are generated at the lower part of the columns and local buckling appears at the column. In this study, axial compression test and beam-column test were conducted for existing CFT square column specimens and those reinforced with carbon fiber sheets (CFS). The variables for axial compression test were width-thickness ratio and the number of CFS layers and those for beamcolumn test were concrete strength and the number of CFS layers. The results of the compression test showed that local buckling was delayed and maximum load capacity improved slightly as the number of layers increased. The specimens' ductility capacity improved due to the additional confinement by carbon fiber sheets which delayed local buckling. In the beam-column test, maximum load capacity improved slightly as the number of CFS layers increased. However, ductility capacity improved greatly as the increased number of CFS layers delayed the local buckling at the lower part of the columns. It was observed that the CFT structure reinforced with carbon fiber sheets controlled the local buckling at columns and thus improved seismic performance. Consequently, it was deduced that the confinement of CFT columns by carbon fiber sheets suggested in this study would be widely used for reinforcing CFT columns.