• Computational Structural Engineering
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• v.11 no.1
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• pp.227-235
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• 1998

A method of calculating the natural frequency corresponding to the first mode of vibration of beams and tower structures, with irregular cross-sections and with arbitrary boundary conditions was developed and reported by D. H. Kim in 1974. This method has been developed for two-dimensional problems including the laminated composite plates and was proved to be very effective for the plates with arbitrary boundary conditions and irregular sections. In this paper, the result of application of this method to the building slabs with passive and active control devices is presented. Finite difference method is used to obtain the deflection influence surfaces needed for this vibration analysis in this paper. The influence of the modulus of the foundation on the natural frequency is thoroughly studied.

• Korean Architects
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• no.8 s.388
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• pp.85-91
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• 2001

10년도 넘었을까 모처럼 유럽을 여행할 기회가 있었다. 우리나라는 온 국토가 공사장이나 진배없던 시절이라 그곳의 풍경이 오히려 이채로웠다. 자동차를 타고 한참을 가야 그것도 별로 크지 않은 공사장을 볼 수 있었고, 그나마 신축공사 보다는 오래된 건물을 보수하는 것들이 더 많았다. 더구나 희한한 것은 대로에 면한 고색 창연한 건물의 외벽만을 텔레비전 세트처럼 남겨두고 그 뒤편에서는 전혀 새로운 공사를 하는 것도 눈에 들어왔다. 조상들의 유적을 외관만이라도 보존하도록 법제화되었으므로 여기저기 떨어져 위치한 100년도 넘은 집에다 따로따로 최신형 공작기계를 설치한 공장에서 제품을 생산하는 비능률을 감수하는 것도 볼 수 있었다. 물론 변두리 신시가지에서는 현대 감각이 물씬한 건물도 신축하고 있었는데, 대체로 리모델링 사업규모가 전체 건축 물량의 50% 정도는 될 것이라는 설명이었다. 필자는 그때 우리도 머지 않아 그런 시절이 도래할 것이라는 확신이 있었다. 더구나 그들의 건물들이 100년 이상을 버티는데 반하여 우리네 것들은 수명이 고작 20~30년 밖에 되지 못할 정도로 부실하기 때문이다. 그때부터 기존 건물의 내력 부족분을 보완하고 용도를 변경하거나 증축을 할 때 어떤 방법이 합리적일까 하는 것에 관심을 가지고 연구하게 되었다. 바닥 슬래브나 보를 잘라버리거나 새로 덧붙이기도 하고 심하면 기둥을 솎아낼 필요가 있을 수도 있다. 그러나 유감스럽게도 대부분의 경우는 그동안 열심히 고안한 방식을 실무현장에 적용할 수 있도록 받아들이는 당사자가 별로 없었다. 첫째 이유는 처음하는 일이라 말하자면 겁이 난다는 것이고, 둘째로는 새로운 방식을 믿고 시행하려 해도 실제로 책임지고 시공하겠다고 나서는 업체를 만날 수 없어서였다. 그래서 그동안 설계뿐만 아니라 시공까지 일일이 간섭하여 어렵게 시행했던 현장 경험들을 소개하여 앞으로 비슷한 조건을 만날 경우 참고할 수 있게 한다. 우선 기둥을 솎아 내는 것을 알아보고 앞으로 기둥, 보, 슬래브, 기초 등의 새로운 보강방법을 소개하고자 한다.

• Computational Structural Engineering
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• v.3 no.1
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• pp.109-116
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• 1990

Live load data in domestic office buildings have been collected in a systematic manner. Based on surveyed data, equivalent uniformly distributed load intensities, which produce the same load effect as the actual spatially varying, live load, have been obtained for various structural members (such as slab, beam, column, etc. ). Influence surface method has been employed to compute load effects under real live load, including beam moment, slab moment as well as axial force in column. The results have been examined to find probabilistic characteristics and relationship between influence area and load intensity (or coefficient of variation). The results were also compared with other survey results and found to be reasonable. Based on the probabilistic load models obtained, the lifetime extreme values have been analyzed and compared with current design loads. Tentative equations applicable to decide more rational design loads are also suggested as functions of influence area.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.24 no.6
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• pp.487-496
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• 2012

Recently, utilization of building foundations as ground-coupled heat exchangers has attracted much attention because they reduce the cost and enhance the heat transfer. The objective of this study is to evaluate the performance of energy-slab ground-coupled heat exchanger installed in a commercial building. In order to demonstrate the energy transfer characteristics of the energy-slab, experiments were conducted from October 2010 to September 2011. The 1-year measurement results showed that the mean EWTs of brine returning from the energy-slab were $9.6^{\circ}C$ in heating season and $24.9^{\circ}C$ in cooling season, which were in a range of design target temperatures. In addition, the geothermal heat pump system with the energy-slab showed on-off operation according to the setting temperatures of secondary fluid in water storage tank. The results also showed that the energy-slab extracted heat of 198.6 kW from the ground and injected heat of 318.9 kW to the ground, respectively.

• Journal of the Korea institute for structural maintenance and inspection
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• v.13 no.1 s.53
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• pp.106-114
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• 2009

The steel design based on the width of transverse crack which is the major factor to affect a long-term performance of continuously reinforced concrete pavement was developed. For this study, twenty-one cities of Texas were selected and the temperature data was collected at those locations during the past ten years. From the data, zero-stress temperatures were calculated by the PavePro program and the widths of transverse crack were analyzed by the CRCP program. The variables used to this numerical analysis were slab thickness, coefficient of thermal expansion of concrete, steel ratio, and design temperature. The total of 448 factorial runs were made and the regression analysis was performed using the results. Steel ratios from the regression equations were backcalculated and a steel design table was proposed.

• Journal of the Korea Concrete Institute
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• v.15 no.6
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• pp.856-865
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• 2003

Current design provisions and guide for performance-based design do not accurately evaluate seismic performance of flat plate system. In the previous companion studies, parametric studies using nonlinear finite element analyses were performed to investigate behavior of the flat plate, and based on the numerical results, design methods that can predict the bending moment-carrying capacity and the corresponding deformability of the flat plate was developed. In the present study, a generalized moment-rotation relation of the flat plate was developed based on the previous studies and the numerical analyses. The proposed method was verified by the comparisons with existing experiments. In addition, the effective stiffness of the flat plate corresponding to 0.2 percent of lateral drift that is generally regarded as the serviceability limit was proposed, so as to evaluate conveniently deflection of the structure subject to wind load.

• Journal of the Korea institute for structural maintenance and inspection
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• v.16 no.2
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• pp.19-30
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• 2012

Due to the fact that the social environment is improved and the urban development is stabilized, the demand of new construction of apartment becomes slowdown. Accordingly, there are many researches to lengthen the service life of the existing apartment through the remodeling and its importance is continuously rising. However, reliable design specifications and guidelines for the design of remodeling with partial demolition are not provided yet in Korea. Specially, in the apartment remodeling, slab collapse accidents take major portion in all accidents that reported by Korean Government. It is very important to prevent intial crack of slab because intial crack could cause severe accident like collapse of all structure in a short period of time. The purpose of this study is to develop structural guidelines that could guarantee the structural safety and serviceability of slab structure and could be adopted in Korean remodeling with partial demolition. There are mainly two components to determine structural behavior of slab structure. One is the shape of slab structure and the other is load which is resisted by the slab structure. In this study, the weight per unit volume of concrete debris and concrete strength are estimated through the analysis of previous researches to recognize the relationship between the shape of slab and load that loaded on the slab. Accordingly, approximately 300 pieces of floor plan are collected and analyzed. The finite element analysis is conducted using these analyzed and estimated results. From the finite element analysis results, the limited stacking height of debris is suggested and the stacking method is also discussed. In addition, to find the relationship between movement of demolition equipment and structural behavior of slab, the static and dynamic loading tests are conducted. From the results of loading tests, the impact factor which will be considered in the remodeling design could be estimated.

• The Journal of Engineering Geology
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• v.16 no.1 s.47
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• pp.97-107
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• 2006

Or this study, prevailing design and construction methods of dam under various unfavorable conditions are summarized. for example, foundation treatment with large scale alluvium site or weathered rock mass, dam constructing techniques with unfavorable topographic conditions are studied for the better understanding of relating engineers. Also, zoning by using weak rocks and sand-gravel fill techniques are summed up.

• Proceedings of the Korea Concrete Institute Conference
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• 2006.05a
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• pp.458-461
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• 2006

Early age cracking of concrete is a widespread and complicated problem, and diverse applications in practical engineering have focused on this issue. Since massive concrete base slab composes the infrastructure of other concrete structures such as pier, concrete dam, and high rise buildings, early age cracking of that is considered as a crucial problem. In this study, finite element analysis (FEA) implemented with the age-dependent microplane model was performed. For a massive concrete base slab, cracking initiation and propagation, and deformation variation were investigated with concrete age. In massive concrete slab, autogenous shrinkage increases the risk of early age cracking and it reduces reinforcement effect on control of early age cracking. Gradual crack occurrence is experienced from exterior surface towards interior of the slab in case of combined hydration heat and autogenous shrinkage. FEA implemented with enhanced microplane model successfully simulates the typical cracking patterns due to edge restraint in concrete base slab.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.5
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• pp.263-274
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• 2018

In this study, the applicability and external/internal stability of a MSEW abutment with a slab were investigated. Structural analysis of slab bridges between 10 ~ 20.0 m and thicknesses of 0.7 ~ 0.9 m was carried out to calculate the reaction forces due to dead and live loads acting on the bridge supports. The slab bridge with a length of 20.0 m satisfied the allowable contact pressure of 200 kPa for the true MSEW abutment. Because the external stability of the true MSEW abutment was dominated by the geometry of the MSE wall, the change in the factor of safety due to the load of the super-structure is small. Because the stiffness of the foundations is fixed and the load of the super-structure is increased, the factor of safety of the bearing capacity was reduced. As the load of the super-structure was increased, the horizontal earth pressure of the true MSEW abutment increased greatly. As a result, the pullout and fracture of the uppermost reinforcement, which are the factors of safety, did not meet the design criteria. Therefore, it is necessary to increase the pullout resistance and the long-term allowable tensile force of the reinforcement placed on the top of the reinforced soils to ensure efficient design and performance of a true MSEW abutment.