• International Journal of Concrete Structures and Materials
• /
• 제10권4호
• /
• pp.425-434
• /
• 2016

In this experimental study, six post-tensioned light weight concrete (LWC) continuous one-way slabs were tested in the following manner: the flexural behaviors of the members were compared with the calculations from the existing standards. The test also examined the effect of prestressing in tendons and proper prestress conditions to reduce the deflection and crack width, and to enhance the flexural capacity and ductility of LWC members. Flexural capacity and stress increments in unbonded tendons of the specimens were compared with those of the simply supported normal and the lightweight concrete members. The suggested safety limit from the American Concrete Institute (ACI) regulation on the maximum capacity and the stress incremental in unbonded tendons were also compared with the test results under simple and continuous supporting conditions.

• 한국철도학회:학술대회논문집
• /
• 한국철도학회 2008년도 추계학술대회 논문집
• /
• pp.1169-1177
• /
• 2008

The system of the railway signaling using the track transmits the approved speed to the location of a train and it. Referring to the way of transmitting train control information, there are the one transmitting it to the on-board system of a train using the direct track, the another transmitting it establishing an instrument, and the other transmitting an instrument by a railway track. The one is the method using the direct track as a conductor for composing the part of the track and attaining the information controlling a train by transmitting a signal to the track. It is used for the high-speed railway and the subway. The method using the track attains information by transmitting it to returned information, and the on-board system of a train attains it by magnetic coupling. Because many reinforcing bars on the concrete slab track are used, interaction between a rail and a reinforcing bar that is not produced on ballast track is made. Due to the interaction, the electric characteristic of rail is changed. In the current paper, we numerically computed the coupling coefficient between the rail and the reinforcing bar based on the concrete slab track throughout the model related to the rail and the reinforcing bar using the concrete slab track that is used in the second interval of the Gyeongbu high-speed railway, and we defined the coupling coefficient not changed in the electric characteristic of rail in the condition that there is no interaction between the rail and the reinforcing bar.

• 한국철도학회:학술대회논문집
• /
• 한국철도학회 2008년도 춘계학술대회 논문집
• /
• pp.691-706
• /
• 2008

ATP(Automatic Train Protection) system in railway signaling system is the important one grasping the position and velocity of a train. The wayside transmitter of ATP system is installed between rails. In concrete slab track, the signal current using wayside transmitter of ATP system is influenced by reinforcing bars. The magnetic coupling between reinforcing bars and wayside transmitter of ATP system as a filter makes an input current distorted. So, it makes an alternating current signal with a desirable size not transmit to on-board system of a train. Way to decrease the distortion of an input current signal frequency is to avoid maximum induction current frequency. And the induction phenomenon between reinforcing bars insulated and wayside transmitter of ATP system does not occur. In this paper, we represent the model about wayside transmitter of ATP system and reinforcing bars on the concrete slab tracks, and calculated the parameters demanded for the model. Also, we demonstrated it through the Maxwell program. Furthermore, we calculated impedance on wayside transmitter used in KVB system and ERTMS/ETCS system which are a kind of ATP system, frequency response of induction current, using the Matlab, and demonstrated the validity of it, using the PSpice program.

• 한국구조물진단유지관리공학회 논문집
• /
• 제26권4호
• /
• pp.81-90
• /
• 2022

이 연구에서는 일방향 콘크리트 슬래브를 대상으로 하여, 철근을 사용한 경우와 CFRP 보강근을 사용한 경우에 대해 보강근 사용량에 따른 휨강도와 처짐 및 균열폭을 비교하여 평가하였으며, CFRP 보강근 콘크리트 슬래브의 휨설계의 지배적인 성능과 효율적인 휨설계 방안에 대해 검토하였다. CFRP 보강근을 사용한 콘크리트 슬래브는 철근을 사용한 경우에 비해 동일한 보강근량에서 더 큰 설계휨강도를 얻을 수 있는 반면, 처짐 및 균열폭은 상대적으로 훨씬 크게 발생한다. CFRP 보강근을 사용한 콘크리트 슬래브에서는 최대균열폭이 설계의 지배적인 요인으로 작용하는 것으로 확인하였으며, 효율적 휨설계를 위해서는 허용균열폭을 0.7 mm로 완화하여 적용할 필요가 있으며, 작은 직경의 보강근 적용을 검토할 필요가 있음을 제시하였다.

• 한국구조물진단유지관리공학회 논문집
• /
• 제19권6호
• /
• pp.95-102
• /
• 2015

최근 교량의 노후화에 따른 유지관리 활동이 교통체증, 환경오염, 막대한 비용의 소모로 인하여 어려움을 겪으면서 조립식교량 공법을 이용하는 모듈러 교량 연구가 진행 중이다. 본 연구는 모듈러 교량과 관련된 연구의 일환으로 연결부를 가지는 1방향 모듈러 슬래브를 대상으로 반복하중 재하시 단면2차모멘트의 변화를 분석하고 콘크리트구조기준의 유효단면2차모멘트 식과 비교하였다. 반복하중 재하 실험을 위하여 일체형, 모듈러 실험체 각각 1개씩을 제작하였다. 실험결과, 모듈러 실험체는 일체형 실험체의 비슷한 휨 성능을 가지고 있었으나, 극한 변위는 20% 부족한 모습을 보였다. 반복하중 재하 실험에서는 모듈러 실험체는 일체형 실험체와는 상이한 처짐 거동을 보였고 단면2차모멘트의 변화가 상이하였다. 또한 콘크리트구조기준의 유효단면2차모멘트 계산식은 모듈러 슬래브의 단면2차모멘트를 적절히 반영하지 못하고 있음을 확인하였고, 실험값을 기반으로 하중과 균열모멘트의 비율을 새로운 값인 4.53을 구하였다.

• 대한토목학회논문집
• /
• 제26권1A호
• /
• pp.183-190
• /
• 2006

2거더교를 위한 장지간 바닥판의 설계에서 바닥판의 안전성과 사용성을 만족시키면서 두께를 줄여 자중을 최소화하는 것은 중요한 요소 중의 하나이다. 이 논문에서는 2거더교를 위한 횡방향 프리스트레스트 콘크리트 바닥판의 설계 최소두께와 배근상세를 안정성, 사용성을 고려하여 제시하였다. 대상 교량은, 실용적인 2거더교를 대표할 수 있는 교량으로, 교량길이 40 m의 단순교이다. 대상교량의 바닥판의 지간을 4 m~12m로 변화시켜 가며 분석하였다. 바닥판의 이방성 거동을 고려하여 최소단면을 일방향 슬래브로 설계하고, 균열폭과 피로강도를 평가하였으며, 처짐제한을 충족시킬 수 있는 최소 수준의 두께와 비교하였다. 연구결과, 피로내구성의 확보를 위해서는 직경 16 mm이하의 철근을 사용하는 것이 좋으며, 지간이 8 m를 넘는 장지간 바닥판은 처짐에 대한 사용성이 두께 결정의 지배적 요소임을 확인하였다. 또한, 현행 도로교 설계기준의 배력 철근량 규정을 적용하면 지간 4 m 이상의 바닥판에서는 지간 3 m 이하의 바닥판에서 기대되는 정도의 교축방향의 구조적 연속성을 확보할 수 없는 것으로 나타났다.

• 한국안전학회지
• /
• 제27권3호
• /
• pp.104-110
• /
• 2012

It is a common practice to design basement walls acting as a one-way slab or plate with idealized boundary conditions, resulting in potentially inefficient design. The walls are often supported by buttress columns and side walls in the vertical direction, thereby acting as a two-way slab. In this study, structural behavior of single-story, three-span basement wall subjected to lateral soil pressure was investigated. Three dimensional finite element analyses were conducted to determine the force distribution on the wall. Based on the numerical studies, a regression analysis was carried out to determine the design values of moments in vertical and horizontal directions as well as shear forces on the wall and design charts are developed. The proposed design method with accompanying design charts would enable practicing engineers to estimate member forces on the wall for preliminary design purpose without resorting to finite element analysis. Numerical examples demonstrated the applicability of the proposed method.

• Advances in concrete construction
• /
• 제2권2호
• /
• pp.91-108
• /
• 2014

This paper presents a nonlinear finite element analysis (FEA) in order to investigate the flexural performance of one-way slabs strengthened by epoxy-bonded steel plates. Four point loading scheme is selectively chosen. A model is developed to implement the material constitutive relationships and non-linearity. Five Slabs were modeled in FEM software using ABAQUS. One slab was unstrengthened control slab and the others were strengthened with steel plates with varying the plate thickness and configuration. In order to verify the accuracy of the numerical model, a comparison was done between the experimental results available in the literature and the proposed equations by ACI 318-11 for the calculation of ultimate load capacities of strengthened slabs, the agreement has proven to be good and FEA attained accurate results compared with ACI code. A parametric study was also carried out to investigate the influence of thickness of steel plate, strength of epoxy layer and type of strengthening plate on the performance of plated slabs. Also, the practical and technical feasibility of splitting the steel plate in strengthening process has been taken into account. For practical use, the author recommended to use bonded steel plate as one unit rather than splitting it to parts, because this saves more effort and reduces the risk of execution errors as in the case of multiple bonded parts. Both techniques have nearly the same effect upon the performance of strengthened slabs.

• Structural Engineering and Mechanics
• /
• 제49권4호
• /
• pp.449-461
• /
• 2014

The use of low-ductility welded wire fabric (WWF) as a main tensile reinforcement in concrete slabs compromises the ductility of concrete structures. Lower ductility in concrete structures can lead to brittle and catastrophic failure of the structures. This paper presents the experimental study carried out on eight simply supported one-way slabs to study the structural behavior of concrete slabs reinforced with low-ductility WWF and steel fibers. The different types of steel fibers used were crimped fiber, hooked-end fiber and twincone fiber. The experimental results show that the ductility behavior of the slab specimens with low-ductility reinforcement was significantly improved with the inclusion of $40kg/m^3$ of twincone fiber. Distribution of cracks was prominent in the slabs with twincone fiber, which also indicates the better distribution of internal forces in these slabs. However, the slab reinforced only with low-ductility reinforcement failed catastrophically with a single minor crack and without appreciable deflection.

• Computers and Concrete
• /
• 제14권5호
• /
• pp.563-575
• /
• 2014

Concrete which is a composite material is frequently used in construction works. Properties and behavior of concrete are significant under the effect of different loading cases. Impact loading which is a sudden dynamic one may have destructive effects on structures. Testing apparatuses are designed to investigate the impact effect on test members. Artificial Neural Network (ANN) is a computational model that is inspired by the structure or functional aspects of biological neural networks. It can be defined as an emulation of biological neural system. In this study, impact parameters as acceleration and impact force values of a reinforced concrete slab are obtained by using a testing apparatus and essential test devices. Afterwards, ANN analysis which is used to model different physical dynamic processes depending on several variables is performed in the numerical part of the study. Finally, test and predicted results are compared and it's seen that ANN analysis is an alternative way to predict the results successfully.