• Journal of Korean Society of Steel Construction
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• v.9 no.2 s.31
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• pp.205-220
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• 1997

The objective of this study is to investigate the structural behavior of concrete-filled steel tubular column-H beam connections with exterior stiffeners. As a preliminary test, simple tensile test on the column to H-beam flange connections stiffened were conducted The paramaters of tensile test are the thickness(T=9, 12, 15m) and the width(W=50, 75, 100, 150mm) of exterior stiffeners. The simple tensile test were conducted to 7 kinds of specimens. Estimating the load, displacement, and strain from each kind, results of simple tensile test were compared with results of second test. On the basis of simple tensile test, test on the column to H-km connections stiffened with the sames under monotonic and cyclic load were conducted. Specimens of 5 for the second experiment were made. In analysis, comparing each strengthes and stiffnesses we estimated deformation capacity. Comparing and estimating each yielding strength ratios and maxium-strength ratios on the basis of yield line theory, new strength formula of beam-to-column connections was suggested.

• Journal of the Earthquake Engineering Society of Korea
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• v.5 no.3
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• pp.1-8
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• 2001

Seismic design forces for bridge components may be determined by modifying elastic member forces of design earthquakes using appropriate response modification factors according to the national design code of bridges Modeling technique of pile foundation system is one of the important parameters which greatly affects the results in the process of the elastic seismic analysis of a bridge system with pile foundation. In this paper, a approximate and simplified modeling technique of a pile foundation system for the practical purposes is presented. The modeling technique is based on the stiffnesses of pile foundation during earthquake. The horizontal stiffnesses are determined from the resistance-deflection curves derived from the results of dynamic field tests using cyclic loads and the vertical stiffness includes the effects of the end bearing capacities and side friction of piles as well as the pile compliances under the expected vertical load level. The applicability of the proposed technique has been validated through the some example bridge analyses.

• Journal of Korean Society of Steel Construction
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• v.9 no.3 s.32
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• pp.377-390
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• 1997

The objective of this study is to investigate the structural behavior of concrete-filled steel tubular column to H-beam connections with reinforced bar. As a preliminary test, simple tensile test on the column to H-beam connections stiffened were conducted. The parameters of tensile test are the diameters of each rebars. The simple tensile test were conducted to 5 kinds of specimens. Estimating the load. displacement and strain for specimens, the result of tensile test were compared with the results of main test. On the basis of simple tensile test, tests are conducted to montonic and cyclic loading column to H-beam connections with the same diameters of rebars. Specimens of 5 are made for monotonic and cyclic loading test. In analysis, estimating the yielding strength and maximum strength of specimens on the basis of yield line theory, strength formula of beam-to column connections with concrete-filled steel tubular column was suggested.

• International Journal of Highway Engineering
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• v.2 no.4 s.6
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• pp.101-109
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• 2000

This study was performed to estimate fatigue life of polymer-modified and reinforced overlay asphalt mixtures with respect to reflection cracking in asphalt overlay pavement. In order to achieve the goal, the expedited reflection cracking test method was developed and applied to various mixtures and the results were compared one another with respect to the resistant characteristics of reflection cracking. The theoretical prediction equation of fatigue life for each mixture was suggested based on statistical analysis of experimental test results in the flexural failure mode. Since coefficients of correlation between estimated values and measured values were very high ($r^2=0.95$ or higher), the prediction model can be used for relative comparison of various pavement overlay choices to be used in the field.

• Journal of Korean Society of Steel Construction
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• v.10 no.2 s.35
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• pp.161-175
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• 1998

The objective of this study is to investigate the structural behavior of Concrete-Filled Steel Tubular Column-H Beam connections with plate stiffeners. The first, we made experiment on the Column to H-beam flange connections stiffened with simple tensile loading. The paramaters of tensile experiment are the area of each plates. The simple tensile experiment is conducted to 5 kinds of specimens. Eestimating the load, displacement, and strain from each kind, we compared them with results of second experiment. The second, we made experiment on the Column to H-beam connections stiffened with the sames under monotonic and cyclic load. we made specimens of 5 for the second experiment. In analysis, comparing each strengthes and stiffnesses we estimated deformation capacity. Comparing and estimating each yielding strength ratios and maxium-strength ratios on the basis of Yield line theory, we suggested new Strength Formula of Beam-to-Column Connections.

• Journal of the Korean Geotechnical Society
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• v.22 no.10
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• pp.173-181
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• 2006

A Two Mobilized-Plane Model is proposed for monotonic and cyclic soil response including liquefaction. This model is based on two mobilized planes: a plane of maximum shear stress, which rotates, and a horizontal plane which is spatially fixed. By controlling two mobilized planes, the model can simulate the principal stress rotation effect associated with simple shear from different $K_0$ states. The proposed model gives a similar skeleton behaviour for soils having the same mean stress, regardless of $K_0$ conditions as observed in laboratory tests. The soil skeleton behaviour observed in cyclic drained simple shear tests, including compaction during unloading and dilation at large strain is captured in the model. Undrained monotonic and cyclic response is predicted by imposing the volumetric constraint of the water on the drained or skeleton behaviour. This constitutive model is incorporated into the dynamic coupled stress-flow finite difference program of FLAC (Fast Lagrangian Analysis of Continua). The model was first calibrated with drained simple shear tests on Fraser River sand, and verified by comparing predicted and measured undrained behaviour of Fraser River sand using the same input parameters.

• Journal of the Korea Concrete Institute
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• v.24 no.4
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• pp.399-406
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• 2012

Beam-column joints are generally recognized as the critical regions in the moment resisting reinforced concrete (RC) frames subjected to both lateral and vertical loads. As a result of severe lateral load such as seismic loading, the joint region is subjected to horizontal and vertical shear forces whose magnitudes are many times higher than in column and adjacent beam. Consequently, much larger bond and shear stresses are required to sustain these magnified forces. The critical deterioration of potential shear strength in the joint area should not occur until ductile capacity of adjacent beams reach the design demand. In this study, a method was provided to predict the deformability of reinforced concrete beam-column joints failing in shear after the plastic hinges developed at both ends of the adjacent beams. In order to verify the deformability estimated by the proposed method, an experimental study consisting of three joint specimens with varying tensile reinforcement ratios was carried out. The result between the observed and predicted behavior of the joints showed reasonably good agreement.

• Journal of the Korea institute for structural maintenance and inspection
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• v.24 no.4
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• pp.10-17
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• 2020

The recent earthquake in Korea caused large and small damages to many school building. School building is an important building that is used as a shelter in the event of disaster. Among the seismic retrofit methods, the internal steel braced frame type method is used for its relatively easy construction and excellent performance. In this study, the maximum shear force and displacement were compared and examined by applying the brace frame to existing concrete school buildings. As a result, we verified the adequacy of the analytical model and compared and examined the effect of brace-height ratio on the span of the existing school buildings. The adequacy of the maximum shear force and displacement relationship can be confirmed in the model with a length of 0.3. In addition, seismic frame was applied to the actual non-seismic reinforced concrete school building, and the seismic performance was evaluated by nonlinear static analysis(Push-over analysis) according to the ratio of brace-height. As a result, the increase of the brace-height according to the brace-height ratio has the effect of increasing the maximum shear force and maximum load at the performance point. But the collapse of the braced frame due to the increase in the lateral stiffness occurred, indicating that seismic retrofit according to the proper brace-height is necessary. Therefore, in the seismic retrofit design of brace frame of existing school building, it is necessary to select the proper brace-height after retrofit analysis according to the brace-height ratio.

• Journal of the Earthquake Engineering Society of Korea
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• v.6 no.4
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• pp.65-73
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• 2002

It has been recognized that the damage control must become a more explicit design consideration. In an effort to develop design methods based on performance it is clear that the evaluation of the nonlinear response is required. The methods available to the design engineer today are nonlinear time history analyses, monotonic static nonlinear analyses, or equivalent static analyses with simulated nonlinear influences. Some building codes propose the capacity spectrum method based on the nonlinear static analysis(pushover analysis) to determine the earthquake-induced demand given by the structure pushover curve. These procedures are conceptually simple but iterative and time consuming with some errors. This paper presents a nonlinear direct spectrum method(NDSM) to evaluate seismic performance of structures, without iterative computations, given by the structural initial elastic period and yield strength from the pushover analysis, especially for MDF(multi degree of freedom) systems. The purpose of this paper is to investigate the accuracy and confidence of this method from a point of view of various earthquakes and unloading stiffness degradation parameters. The conclusions of this study are as follows; 1) NDSM is considered as practical method because the peak deformations of nonlinear system of MDF by NDSM are almost equal to the results of nonlinear time history analysis(NTHA) for various ground motions. 2) When the results of NDSM are compared with those of NTHA. mean of errors is the smallest in case of post-yielding stiffness factor 0.1, static force by MAD(modal adaptive distribution) and unloading stiffness degradation factor 0.2~0.3.

• Journal of the Korean Geotechnical Society
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• v.23 no.6
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• pp.37-51
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• 2007

In this study, pile load tests have been carried out to develop new P-y curves and then, to investigate the effects of pile rigidities on laterally loaded offshore drilled shafts in Incheon marine clay. This paper consists mainly of two parts: the first part, performance of a series of lateral load tests on small- and full-scale piles under one- and two-way loadings and the second part, comparison between the measured and predicted results by using O'Neill's and Matlock's clay models. Based on the results obtained, it is shown that relatively good agreements in bending moments and lateral displacements were obtained between the measured results using calculated P-y curves and predicted ones by O'Neill's and Matlock's clay models. The cases were considered with varying rigidity factors based on pile diameter, length and subgrade soil reaction. Through comparisons, it is found that soil P-y curve influences highly the behavior of flexible pile rather than that of rigid pile.