• 한국산업융합학회 논문집
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• 제5권3호
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• pp.261-268
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• 2002

In this paper, the shape optimization is considered over the upper slab of reinforced concrete culvert. The sequential linear programming method (SLP) is used as a rational approach to this shape optimization. To make a comparison between the arch shaped member and the straight member for the upper slab, the culverts with 5~20m earth height were adopted. It is shown that the optimum rise/span is about 7%-13%, and the arch shaped member is more cheap (over 10%) than the straight member for the construction cost.

• 한국도로학회논문집
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• 제14권6호
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• pp.25-35
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• 2012

PURPOSES : Hollows are easily made, and bearing capacity can be lowered near underground structures because sublayers of pavement settle for a long time due to difficult compaction at the position. If loadings are applied in this condition, distresses may occur in pavement and, as the result, its lifespan can decrease due to the stress larger than that expected in design phase. Although reinforced slab is installed on side of box culvert to minimize the distresses, length of the reinforced slab is fixed as 6m in Korea without any theoretical consideration. The purpose of this paper is investigating the behavior of concrete pavement according to the cover depth of the box culvert ad the length of the reinforced slab. METHODS : The distresses of concrete pavement slabs were investigated and cover depth was surveyed at position where the box culverts were located in expressways. The concrete pavements including the box culverts were modeled by finite element method and their behaviors according to the soil cover depth were analyzed. Wheel loading was applied after considering self weight of the pavement and temperature gradient of the concrete pavement slab at Yeojoo, Gyeonggi where a test road was located. After installing pavement joint at various positions, behavior of the pavement was analyzed by changing the soil cover depth and length of the reinforced slab. RESULTS : As the result, the tensile stress developed in the pavement slab according to the joint position, cover depth, and reinforced slab length was figured out. CONCLUSIONS : More reasonable and economic design of the concrete pavement including the box culvert is expected by the research results.

• 한국안전학회지
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• 제27권2호
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• pp.25-32
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• 2012

In this study, the effect of blast furnace slag on precast concrete culvert was assessed by measuring the flexural strength using to full scaled box culvert. As a result, the initial cracking load and yield load of reinforced concrete box converts are increased in comparison with those of the normal concrete box culvert, but the ultimate load is decreased slightly. It can be concluded that use of blast furnace slag induce to flexural strength in precast concrete box culvert greatly improved the serviceability.

• 한국농공학회:학술대회논문집
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• 한국농공학회 1999년도 Proceedings of the 1999 Annual Conference The Korean Society of Agricutural Engineers
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• pp.212-218
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• 1999

In this study , Computer programs for the optimum and automation desgin of reinforced concrete box culvert were developed. It was shown that even though the strarting points and optimization method are different the objective function and optimum design variables converge to a value within a close range respectively, and consequently the optimum design program developed in the study is reliable and stron. 3D-design drawing can be drawn using automation desgin computer program developed in this study.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1990년도 봄 학술발표회 논문집
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• pp.84-89
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• 1990

The objective of this study is to optimize the section of RC box culvert and develop a CAD system for drawing. This paper consists of three parts. In the first part, the external load conditions are systematized by using the literatures and specifications. In the second one, the RC box culvert is optimized using the SUMT algorithm. Sizing variables, and steel ratio are taken as design variables, and a cost function as the objective function. The stress and side constraints are derived from the Korea Concrete Specifications for the ultimate strength design. Finally, a data base and CAD system is developed for the drawing of the optimized section of RC box culverts.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 1999년도 토목섬유 학술발표회 논문집
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• pp.105-116
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• 1999

The Inchon International Airport site was formed by reclaimed soil from the sea. The average thickness of soft soil Is about 5 m and most of soft soils are normally consolidated or slightly over consolidated. There are many box culverts which are being constructed under the runways in the airfield. Sometimes, differential settlement can be occurred in the adjacent of box culvert or underground structures at the top layer of runway Soil compaction at very near to the structure is not easy all the time. Thus, one layer of geogrid was placed at the bottom of lean concrete layer for the concrete paved runway and at the middle of cement stabilized sub-base course layer for the asphalt paved runway. The length of geogrid reinforcement is 5m from the end of box culvert for both sides. The extended length of geogrid was 2m from the end of backfill soil in the box culvert. The tensile strength tests of geogrid were conducted for make sure the chemical compatibility with cement treated sub-base material. The location of geogrid placement for the concrete paved runway was evaluated. The construction damage to the geogrid could be occurred. Because the cement treated sub-base layer or lean concrete was spread by the finisher. The magnitude of tensile strength reduction was 1.16%~1.90% due to the construction damage and the ultimate tensile strength is maintained with the specification required. Total area of geogrid placement in this project is about 50,000 $m^2$.

• KCI Concrete Journal
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• 제13권1호
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• pp.43-51
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• 2001

Although portland cement concrete is one of the most universal construction materials, it has some disadvantage such as shrinkage, which is an inherent characteristic. Because of this shrinkage, combined with the low tensile strength of the material, cracks of varying sizes can be found in every reinforced concrete. To prevent this cracking, keeping the concrete in compression by mechanical prestress has been used. This study discusses application of expansive additives for concrete to improve the serviceability of precast concrete box culvert by inducing chemical prestress. For this purpose, both expansive concrete slabs and normal concrete slabs are tested to verify the effect of expansive additives. Then the failure tests of the fullscale precast box culverts were carried out and the critical aspects of the structural behavior were investigated. The result of the material testis shows that the optimal proportion of expansive additives is 13 percent of cement weight, and the properties of expansive concrete are the same as those of normal concrete in that proportion. Both the experimental cracking load and service load of the expansive concrete members are increased in comparison with those of the normal concrete, but the ultimate load is decreased slightly. In addition to the above results, the deformation of expansive concrete member is lets than that of normal concrete member, and permanent strain which results from cyclic load is decreased. It can be concluded that the use of expansive additives to induce chemical prestress in precast concrete box culvert greatly improves the serviceability.

• 한국구조물진단유지관리공학회 논문집
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• 제16권5호
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• pp.121-128
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• 2012

이 논문에서는 대표적 수치해석에의 균열처리 방법으로 손상모델 기반의 분산균열모델을 체택하여 구조내력을 산정하였다. 또한 전력구 구조물의 실구조 모델링을 위해 3차원 해석방법을 택하였으며 3차원 콘크리트 구성모델로는 현재 3차원 모델중 콘크리트의 다축압축, 인장균열을 효과적으로 모사하는 미소면 모델(Microplane model)을 재료모델로 사용하여 비선형 유한요소해석을 수행하였다. SFRC의 인장연화곡선을 얻기 위해 역해석법을 사용하였으며, 역해석으로 구한 인장연화곡선이 실험결과와 아주 잘 일치함을 보였다. 하중-균열폭 관계를 입력값으로 사용한 역해석 결과와 하중-CMOD 관계를 사용한 역해석 결과는 서로 잘 일치하는 경향을 나타냈다. 이 논문에서는 실험으로부터 측정된 균열폭 데이터와 수치해석시의 손상지수와의 관계를 도출하여으며, 이와 같은 결과는 향후 균열탐사를 통한 구조물의 잔존 구조내력 산정에 적용할 수 있으리라 판단된다.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1999년도 봄 학술발표회 논문집(I)
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• pp.789-792
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• 1999

Reinforced concrete structures covered creek for road vehicle located in urban areas have been experiencing corrosion of concrete and reinforcing steel caused by $H_2S$ gases generated by anaerobic bacterial. H2S gases react with oxygen and water to form sulfuric acid ($H_2SO_4$). This acid chemically attacks concrete, and sulfate ions penetrate into the concrete, causing rebar corrosion. In this work, to determine the conditions of RC culvert boxes which were constructed in the 1970s, various tests were conducted, including carbonation depth, compressive strength, half-cell potential measurements, and XRD analyses. Results indicated that the concrete deterioration was caused by sulfate attack and rebar corrosion. This paper discusses the evaluation on the durability of reinforced concrete structures covered creek for road vehicle.

• Structural Engineering and Mechanics
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• 제28권3호
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• pp.281-294
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• 2008

In this paper, linear elastic isotropic structures under the effects of both stochastic operators and stochastic excitations are studied. The analysis utilizes the spectral stochastic finite elements (SSFEM) with its two main expansions namely; Neumann and Homogeneous Chaos expansions. The random excitation and the random operator fields are assumed to be second order stochastic processes. The formulations are obtained for the system solution of the two dimensional problems of plane strain and plate bending structures under stochastic loading and relevant rigidity using the previously mentioned expansions. Two finite element programs were developed to incorporate such formulations. Two illustrative examples are introduced: the first is a reinforced concrete culvert with stochastic rigidity subjected to a stochastic load where the culvert is modeled as plane strain problem. The second example is a simply supported square reinforced concrete slab subjected to out of plane loading in which the slab flexural rigidity and the applied load are considered stochastic. In each of the two examples, the first two statistical moments of displacement are evaluated using both expansions. The probability density function of the structure response of each problem is obtained using Homogeneous Chaos expansion.