• Structural Engineering and Mechanics
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• 제57권5호
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• pp.937-949
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• 2016

Fiber reinforced polymer (FRP) applications in the structural engineering field include concrete-FRP composite systems, where FRP components are either attached to or embedded into concrete structures to improve their structural performance. This paper presents the results of an analytical study conducted using finite element model (FEM) to simulate the behavior of three-points load beam reinforced with GFRP and/or steel bars. To calibrate the FEM, a small-scale experimental program was carried out using six reinforced concrete beams with $200{\times}200mm$ cross section and 1000 mm length cast and tested under three point bending load. The six beams were divided into three groups, each group contained two beams. The first group was a reference beams which was cast without any reinforcement, the second group concrete beams was reinforced using GFRP, and the third group concrete beams was reinforced with steel bars. Nonlinear finite element simulations were executed using ANSYS software package. The difference between the theoretical and experimental results of beams vertical deflection and beams crack shapes were within acceptable degree of accuracy. Parametric study using the calibrated model was carried out to evaluate two parameters (1) effect of number and position of longitudinal main bars on beam behavior; (2) performance of concrete beam with composite longitudinal reinforcement steel and GFRP bars.

• Advances in concrete construction
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• 제8권1호
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• pp.9-19
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• 2019

This paper describes an experimental investigation on hybrid fiber reinforced concrete (HYFRC) beams. And the main aim of this present paper is to examine the dynamic characteristics and damage evaluation of undamaged and damaged HYFRC beams under free-free constraints. In this experimental work, totally four RC beams were cast and analyzed in order to evaluate the dynamic behavior as well as static load behavior of HYFRCs. Hybrid fiber reinforced concrete beams have been cast by incorporating two different fibers such as steel and polypropylene (PP). Damage of HYFRC beams was obtained by cracking of concrete for one of the beams in each set under four-point bending tests with different percentage variation of damage levels as 50%, 70% and 90% of maximum ultimate load. And the main dynamic characteristics such as damping, fundamental natural frequencies, mode shapes and frequency response function at each and every damage level has been assessed by means of non-destructive technique (NDT) with hammer excitation. The fundamental natural frequency and damping values obtained through dynamic tests for HYFRC beams were compared with control (reference) RC beam at each level of damage which has been acquired through static tests. The static experimental test results emphasize that the HYFRC beam has attained higher ultimate load as compared with control reinforced concrete beam.

• 콘크리트학회지
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• 제25권5호
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• pp.17-20
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• 2013

• 콘크리트학회논문집
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• 제25권3호
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• pp.295-304
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• 2013

초고성능 콘크리트(UHPC: Ultra-High Performance Concrete)는 최근 국내외에서 연구가 가장 활발한 분야 중 하나로서 구조물의 장수명화와 경제성 제고에 기여하고 있다. 품질관리 및 공사기간 단축을 위해서는 공장에서 제작된 프리캐스트 방식의 초고성능 콘크리트가 유리하지만, 이 경우에도 프리캐스트 세그먼트 간의 이음부 등 부득이 현장타설로 시공되어야 하는 부분이 존재한다. 그러나 현장타설 시에는 공장 제작 시와는 달리 최적의 양생 조건을 구현하기 어려울 가능성이 크다. 따라서 이 연구에서는 현장에서 예상되는 여러 가지의 열악한 양생 조건을 가정하였을 때 초고성능 콘크리트의 압축강도 발현 경향을 실험적으로 규명하였다. 양생온도, 양생 전 지연시간, 양생 지속시간, 수분 공급 조건을 변수로 두어 공시체를 제작한 후 표준적인 고온습윤양생으로 제작된 공시체의 강도와 비교하였다. 실험 결과를 분석하여 현장에서 타설된 초고성능 콘크리트를 양생할 때 요구되는 최소한의 조건을 제안하였다. 이 연구를 통해 초고성능 콘크리트의 현장에서의 활용도를 더욱 높일 수 있을 것으로 기대된다.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2003년도 가을 학술발표회 논문집
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• pp.367-370
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• 2003

This study was carried out to suggest the effective reinforcing method which can evaluate the tensile capacity of cast-in-place anchor with cracks. Currently, cast-in-place anchor is used widely for the fastening of equipment in Korean NPPs. 26 test specimens with a single anchor under 4 cracked conditions are prepared using plain concrete. The distance between crack and anchor and reinforcing materials were selected as the main test variable. The tensile force was applied using a actuator with a capacity of 100 tonf using a displacement control method of 0.5 mm/min velocity. Test results from this result show the combination of carbon plate and epoxy will be more available for repair and reinforcement of equipment foundation system in NPPs. Further experimental work is indeed involving the epoxy injection effect and adjustment of reinforcing location of carbon sheet.

• 콘크리트학회논문집
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• 제25권2호
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• pp.175-185
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• 2013

최근 다른 압축강도로 타설된 프리캐스트 콘크리트(PC)와 현장타설 콘크리트(CIP)의 복합 부재의 사용이 증가하고 있지만 현행 기준에는 서로 다른 강도로 복합화된 부재의 전단강도에 대한 설계 기준이 없다. 그래서 이번 연구에서 서로 다른 압축강도(24 MPa, 60 MPa)로 분리 타설된 보의 전단강도 실험을 수행하여 복합 부재의 전단강도에 대해 알아보았다. 변수로는 단면형상, 휨철근비, 그리고 전단경간비를 고려하였다. 실험 결과 값과 현행 전단 기준식과 단면적비로 계산한 유효 콘크리트 강도를 이용한 예측 값을 비교하였다. 실험 결과를 분석해보면 철근비가 낮고 압축대에 60 MPa가 사용된 실험체들에 대해 설계 기준식을 과대평가하였다. 실험 결과를 기준으로 PC와 CIP 복합부재의 전단설계 기준을 제안하였다.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2006년도 춘계학술발표회 논문집(I)
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• pp.242-245
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• 2006

In this research, a precast concrete slab with two ribs was developed to increase the stiffness of slab. The developed precast slabs are allowed to cast concrete for multi stories and to construct concrete slabs without any props. Seven concrete slabs were tested to investigate the behavior of the developed precast slabs. Test results indicated that the developed slabs showed a similar behavior with the slabs without ribs.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1999년도 학회창립 10주년 기념 1999년도 가을 학술발표회 논문집
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• pp.425-428
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• 1999

This paper presents the evaluation of behavior and the prediction of tensile capacity of anchors that fail concrete, as the design basis for anchorage. Tests of cast-in-place headed anchors, domestically manufactured and installed in uncracked, unreinforced concrete are performed to investigate the behavior of single anchors and multiple anchors with the consideration of various embedment lengths and edge distances.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1994년도 가을 학술발표회 논문집
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• pp.350-355
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• 1994

This study is aimed at the experimental investigation of the influence of the structural parameters such as concrete cover, width of specimen and bar size on the dowel action of reinforcing bari in high strength concrete members. Based on the proper combination of these parameter, a total of 46 specimens has been cast for fc'= 500 ㎏/㎠ and another 46 specimens for fc'= 700 ㎏/㎠, and cured at the laboratory. Comparative analyses have been made for the parametric contribution to the dowel strength from the test results, and a regress equation has been suggested.

• Structural Engineering and Mechanics
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• 제71권4호
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• pp.433-444
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• 2019

Shear studs are often used to connect steel girders and concrete deck to form a composite bridge system. The application of precast concrete deck to steel-concrete composite bridges can improve the strength of decks and reduce the shrinkage and creep effect on the long-term behavior of structures. How to ensure the connection between steel girders and concrete deck directly influences the composite behavior between steel girder and precast concrete deck as well as the behavior of the structure system. Compared with traditional multi-I girder systems, a twin-I girder composite bridge system is more simplified but may lead to additional requirements on the shear studs connecting steel girders and decks due to the larger girder spacing. Up to date, only very limited quantity of researches has been conducted regarding the behavior of shear studs on twin-I girder bridge systems. One convenient way for steel composite bridge system is to cast concrete deck in place with shear studs uniformly-distributed along the span direction. For steel composite bridge system using precast concrete deck, voids are included in the precast concrete deck segments, and they are casted with cast-in-place concrete after the concrete segments are erected. In this paper, several sets of push-out tests are conducted, which are used to investigate the heavier of shear studs within the voids in the precast concrete deck. The test data are analyzed and compared with those from finite element models. A simplified shear stud model is proposed using a beam element instead of solid elements. It is used in the finite element model analyses of the twin-I girder composite bridge system to relieve the computational efforts of the shear studs. Additionally, a parametric study is developed to find the effects of void size, void spacing, and shear stud diameter and spacing. Finally, the recommendations are given for the design of precast deck using void for twin I-girder bridge systems.