• Land and Housing Review
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• v.3 no.4
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• pp.433-449
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• 2012

An experimental investigation was conducted to study the behavior of RC wide beam-column joints with slab subjected to reversed cyclic loads under constant axial load. Six half scale interior wide beam-column assemblies representing a portion of a frame subjected to simulated seismic loading were tested, including three specimens without slab and three specimens with slab. The primary variables were the ratio of column-to-beam flexural capacity ($M_r={\Sigma}M_c/{\Sigma}M_b$ ; 0.77~2.26), ratio of the column-to-beam width (b/H ; 1.54, 1.67). Test results are shown that (1) the current design code and practice for interior joints(type 2) are apply to the wide beam-high strength concrete column. (2) the presence of a slab have an effect on the performance of the wide beam-high strength concrete column interior joints(type 2). therefore in the design of the wide beam-high strength concrete column interior joints(type 2), the width of slab effective as a T beam flange should be considered. It was show that the case of the ratio of column-to-beam flexural capacity is more than 2.0, the effective width of slab are 2 times of an effective depth of wide beam, however if the ratio of column-to-beam flexural capacity is 1.4~2.0, the effective width of slab are not able to be considered.

• Journal of the Korean Geosynthetics Society
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• v.21 no.4
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• pp.101-109
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• 2022

This study describes the results of model experiment to analyze the effect of backfill material types on the behavior of underground facility. In the model experiment, backfill materials around the existing underground facility were applied with soil (Jumunjin standard sand) and CLSM. The displacement of underground facility was analyzed for each excavation stage considering the separation distance between the excavation surface and the backfill area based on the experimental results. When soil was applied as a backfill material, the soil on the back of the excavation surface collapsed by excavation and formed an angle of repose, and the process of slope stability was repeated at each excavation stage. In addition, the displacement of underground facility began to occur in the excavation stage that the failure line of soil passes the installation location of the underground facility. When CLSM was applied as a backfill material, there was almost no horizontal and vertical displacement of the ground regardless of the separation distance from the excavation surface even when excavation proceeded to the backfill depth. Therefore, this result showed that it can have a resistance effect against the lateral earth pressure generated and the collapse of the original ground by adjacent excavation, if a backfill material with high stiffness such as CLSM is applied.

• Journal of the Korean Geotechnical Society
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• v.36 no.12
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• pp.77-86
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• 2020

In this study, the importance of implied strength correction for shallow depths at a region of moderate to low seismicity with primary focus on its effect upon site natural period and mean period of the ground motion is investigated. In addition to the most commonly used Modified Kondner-Zelasko (MKZ) model, this paper uses a quadratic/hyperbolic (GQ/H) model that can capture the stress - strain response at large strains as well as small strain stiffness dependence. A total of six site profiles by downhole tests are used and 1D site response analyses are performed using three input motions with contrasting mean periods. The difference between non-corrected and corrected analyses is conditional on the site period as well as mean ground motion period. The effect of periods is analyzed by correlating them with the effective peak ground acceleration, maximum shear strains and amplification factors. The comparative study reveals that the difference is more prominent in soft sites with long site periods. Insignificant differences are observed when soil profiles are subjected to ground motion with very short mean period.

• Journal of the Korea Concrete Institute
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• v.16 no.1 s.79
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• pp.94-101
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• 2004

This study shows the test results of seven RC beams retrofitted with modified polymer system and parametric study about the effects of tensile strength of retrofitting materials by analytical method on the flexural behavior. The main parameters are the retrofitted depth and length. The beams are loaded to the failure by four-point loading. Test results show that the effect of the retrofitted length on the structural behavior is more significant than that of depth. As the retrofitted depth is increased, the beams represents the brittle failure mode The non-linear analysis is carried out to grasp the effect of the tensile strength of retrofitting material on the structural behavior. As the retrofitted depth and length are increased, the tensile strength becomes more effective so these parameters should be considered to determine the retrofitted area. The analytical results show that failure strength is less than that of experimental results, but the stiffness is vice versa.

• Geotechnical Engineering
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• v.7 no.1
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• pp.41-52
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• 1991

A study of the effects of dynamic pile-soil-structure interactions on the response of super- structures, supported by group piles, are presented in this paper. The dynamic impedance functions of single pile generated by soil-pile interactions are obtained and compared among others using the methods proposed by Novak, Gazetas, and Kuhlemeyer, and using the equivalent cantilever method. Group pile effects are also considered by the following approaches : neglecting interaction effects : group efficiency ratio concept : static interaction approach . and dynamic interaction approach. The responses of a nuclear containment structure are obtained by using the elastic half-space analysis, based on the impedance functions mentioned above. Main conclusions drawn from this study are as follows : 1. The numerical results of the impedance functions calculated by each method were quite different : the Novak's was the smallest, and the Kuhlemeyer's the highest. Considering group effects, similar values in each approach were obtained for the stiffness : the difference was very big for the damping. 2. The top displacement of the structure was reduced by 20% or more by pile installations. However, the base shear force, the base moment, and the resonance frequency were increased by more than two times due to stiffening effect of the ground by pile installations. 3. Whether frequency dependant impedence functions or frequency independant functions were used, the responses of the structure were not so much affected by the choice of the impedance functions. 4. The reduction effect of the top displacement increased with the increase of the maximum ground acceleration.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.35 no.5
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• pp.277-286
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• 2022

The elastic and inelastic responses obtained from the experimental and analytical results of two RC building structures under the service level earthquake (SLE) and maximum considered earthquake (MCE) in Korea were used to weinvestigate the characteristics of the mechanisms resisting shear and torsional behavior in torsionally unbalanced structures. Equations representing the interactive effect of translational drift and torsional deformation on the shear force and torsional moment were proposed. Because there is no correlation in the behavior between elastic and inelastic forces and strains, the incremental shear forces and incremental torsional moments were analyzed in terms of their corresponding incremental drifts and incremental torsional deformations with respect to the yield, unloading, and reloading phases around the maximum edge-frame drift. In the elastic combination of the two dominant modes, the translational drift mainly contributes to the shear force, whereas the torsional deformation contributes significantly to the overall torsional moment. However, this phenomenon is mostly altered in the inelastic response such that the incremental translational drift contributes to both the incremental shear forces and incremental torsional moments. In addition, the given equation is used to account for all phenomena, such as the reduction in torsional eccentricity, degradation of torsional stiffness, and apparent energy generation in an inelastic response.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.1
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• pp.362-370
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• 2019

This study was conducted to investigate effects of 12 weeks of combined exercise training with blood flow restriction (BFR) on body composition (weight, %body fat, lean body mass, body mass index (BMI)) and cardiovascular responses (brachial-ankle pulse wave velocity (ba PWV) and ankle-brachial index (ABI)) in elderly women. Participants (N = 43, Females) were randomly assigned into a combined exercise with BFR (n = 14, BFR), only combined exercise (n =14, EX) or non-exercise control group (n = 15, CON). Two-way repeated measures ANOVA with contrast testing was utilized for data analysis. Alpha was set at p < 0.05. Body composition (weight, %body fat, BMI) in BFR was significantly changed, and %body fat in EX was significantly decreased, but there was no change in the CON. In addition, the right and left ba PWV values in the BFR were significantly decreased, while only the left side ba PWV in EX was significantly decreased and there was no change in the CON. Moreover, the % change and effect size of most variables in the BFR were higher than the EX. Taken together, the results indicate that even though BFR and EX groups performed the same combined exercise training, BFR had additional stimulations of the sympathetic nerve system due to blood flow restriction. Thus, BFR training is more beneficial and has greater effects on body composition and cardiovascular responses in elderly females.

• Journal of the Korea institute for structural maintenance and inspection
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• v.20 no.4
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• pp.94-103
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• 2016

For elevated railway station on which track is connected with superstructure of station, structural vibration level and structure-borne-noise level has exceeded the reference level due to structural characteristics which transmits vibration directly. Therefore, existing elevated railway station is in need of economical and effective vibration reduction method which enable train service without interruption. In this study, structural vibration non-transmissible system which is applied to vibroisolating material for column member is developed to reduce vibration. That system is cut covering material of the column section using water-jet method and is installed with vibroisolating material on cut section. To verify vibration reduction effect and structural performance for structural vibration non-transmissible system, impact hammer test and cyclic lateral load test are performed for 1/4 scale test specimens. It is observed that natural period which means vibration response characteristics is shifted, and damping ratio is increased about 15~30% which means that system is effective to reduce structural vibration through vibration test. Also load-displacement relation and stiffness change rate of the columns are examined, and it is shown that ductility and energy dissipation capacity is increased. From test results, it is found that vibration non-transmissible system which is applied to column member enable to maintains structural function.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.11
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• pp.561-567
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• 2018

This study was carried out to improve the ride quality of high-speed electric multiple unit. Through dynamic analysis of the HEMU-430X, the range of the equivalent conicity with a critical speed of 300 km/h was between 0.05 and 0.25. The initial adopted wheel profile of HEMU-430X was S1002. The equivalent conicity of S1002 with the mileage of more than 40,000 km was about 0.033 and it was confirmed that XP55 is more suitable for stable operation because XP55 has the equivalent conicity of over 0.061. In order to improve ride quality of high-speed electric multiple unit, the change of installation angle of the yaw damper was suggested from $7.35^{\circ}$ to $0^{\circ}$. From sensitivity analysis and optimization, the air spring lateral and vertical stiffness was suggested to be reduced by 30% and the secondary vertical and lateral damper damping coefficient was increased by 50%. By applying this, it was expected that the car body acceleration could be improved by about 20% on average. The HEMU-430X's yaw damper installation angle was changed to $0^{\circ}$ and the damping coefficient of the lateral damper was increased by 30%. When the test run was carried out at the speed of 300 km/h on the Kyungbu high-speed line, the vehicle lateral acceleration had improved by 34.3%. The effect of additional improvement measures proposed in this paper will be tested in the on track test. The riding quality improvement process used in this study can be used to solve ride quality problems that can occur in commercial operation of high-speed electric multiple unit in the future.

• The Journal of Engineering Geology
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• v.27 no.3
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• pp.331-343
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• 2017

In this study to improve stability, workability and economics of the H-Pile+Earth plate or H-Pile+Earth plate+Cutoff grouting currently in use, we had developed HCS method belonging to the retaining wall which is consisting of a combination H-Pile, Plastic Sheet Pile and Steel Square Pipe for gap maintenance and reinforcement of flexible plastic Sheet Pile, and the behavior of each member composing HCS method is investigated by three-dimensional finite element analysis. To numerically analyze the behavior of the HCS method, we have performed extensive three-dimentional finite element analysis for three kinds of plastic Sheet Pile size, two kinds of H-Pile size and three kinds of H-Pile installation interval, one kinds of Steel Square Pipe and three kinds of Steel Square Pipe installation interval. After analyzing the numerical results, we found that the combinations of $P.S.P-460{\times}131.5{\times}7t$ (PS7) and H-Pile $250{\times}250{\times}9{\times}14$ (H250), $P.S.P473{\times}133.5{\times}9t$ (PS9) and H-Pile $300{\times}200{\times}9{\times}14$ (H300) is the most economical because these combinations are considered to have a stress ratio (=applied stress/allowable stress) close to that as the stiffness of H-Pile, plastic Sheet Pile and Steel Square Pipe composite increased, the horizontal displacement of the retaining wall and the vertical displacement of the upper ground decreased. Especially, due to the arching effects caused by the difference in stiffness between H-Pile and plastic Sheet Pile, a large part of the earth pressure acting on plastic Sheet Pile caused a stress transfer to H-Pile, and the stress and displacement of plastic Sheet Pile were small. Through this study, we can confirm the behavior of each member constituting the HCS method, and based on the confirmed results of this study, it can be used to apply HCS method in reasonable, stable and economical way in the future.