• Structural Engineering and Mechanics
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• 제84권3호
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• pp.375-391
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• 2022

This paper discussed and analyzed the interfacial stress distribution characteristic of adjacent cracks in Carbon Fiber Reinforced Polymer (CFRP) plate strengthened concrete slabs. One un-strengthened concrete test beam and four CFRP plate-strengthened concrete test beams were designed to carry out four-point flexural tests. The test data shows that the interfacial shear stress between the interface of CFRP plate and concrete can effectively reduce the crack shrinkage of the tensile concrete and reduces the width of crack. The maximum main crack flexural height in pure bending section of the strengthened specimen is smaller than that of the un-strengthened specimen, the CFRP plate improves the rigidity of specimens without brittle failure. The average ultimate bearing capacity of the CFRP-strengthened specimens was increased by 64.3% compared to that without CFRP-strengthen. This indicites that CFRP enhancement measures can effectively improve the ultimate bearing capacity and delay the occurrence of debonding damage. Based on the derivation of mechanical analysis model, the calculation formula of interfacial shear stress between adjacent cracks is proposed. The distributions characteristics of interfacial shear stress between certain crack widths were given. In the intermediate cracking region of pure bending sections, the length of the interfacial softening near the mid-span cracking position gradually increases as the load increases. The CFRP-concrete interface debonding capacity with the larger adjacent crack spacing is lower than that with the smaller adjacent crack spacing. The theoretical calculation results of interfacial bonding shear stress between adjacent cracks have good agreement with the experimental results. The interfacial debonding failure between adjacent cracks in the intermediate cracking region was mainly caused by the root of the main crack. The larger the spacing between adjacent cracks exists, the easier the interfacial debonding failure occurs.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2005년도 봄학술 발표회 논문집(I)
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• pp.15-30
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• 2005

The increasing amount of structures presenting distress due to reinforcement corrosion is urging the establishment of more accurate calculation methods for the service life of concrete structures. In the present paper, a summary of the different approaches is presented that are able to calculate the expected life of new structures, in certain aggressive environments or the residual life of already corroding structures. The methods for the initiation period are based on the proper calculation of the carbonation front or chloride penetration and on the steel corrosion rate. The methods for the residual load-bearing capacity calculations are based in the use of ' indicators ' or in the evaluation of the reduced section and a structural recalculation.

• Geomechanics and Engineering
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• 제18권4호
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• pp.439-448
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• 2019

The bearing capacity of roadside support is the key problem in gob-side entry retaining technology. To study the cooperative bearing characteristics of the roof-roadside support-floor along the gob-side entry retaining, a mechanical model of the composite structure of the roof-roadside support-floor was first established. A method for determining the structural parameters of gob-side entry retaining was then proposed. Based on this model, adaptability analysis of roadside support was carried out. The results showed that the reasonable width of the gob-side entry roadway was inversely proportional to the mining height, and directly proportional to the bearing strength of the roof and floor. And the reasonable width of the "flexible-hard" roadside support was directly proportional to its own strength, and inversely proportional to the width of the gob-side entry retaining. When determining the position and size of the roadside support along the gob-side entry retaining, the surrounding rock environment should be fully considered. Measured results from case study also show the rationality of the model and calculation method.

• 한국지반공학회논문집
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• 제35권3호
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• pp.5-16
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• 2019

최근 도시 인구의 밀집으로 대형구조물의 건설이 증가하고 있으며 이와 더불어 대형구조물의 기초도 발전하고 있다. 2000년대 말에 일본의 기술을 도입하여 PHC말뚝은 많은 구조물에 사용되고 있다. 최근 PHC말뚝의 장점을 이용하여 흙막이 벽체로의 사용에 대한 연구가 많이 진행되고 있으며, 이 연구에서는 PHC-W 흙막이 벽체를 이용한 건축물 지하증설벽체에서 PHC-W말뚝을 주열식으로 시공하여 연직 압축정재하시험을 실시하였으며, 하중전이 측정을 통하여 PHC-W말뚝의 선단지지력을 산정하였다. 풍화암에 근입된 PHC-W말뚝의 지지력은 기존 PHC말뚝의 지지력과는 차이를 보였으므로, 주열식으로 시공된 PHC-W말뚝의 선단지지력 산정식을 제안하였다. 풍화암에 근입된 PHC-W말뚝의 단위극한선단지지력 산정식으로 주열식 군PHC-W말뚝과 단일PHC-W말뚝에서 각각 $q_b=6.8N_b$와 $q_b=13.3N_b$로 제안할 수 있었다.

• Steel and Composite Structures
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• 제49권2호
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• pp.215-230
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• 2023

Cable-girder anchorage joint is the critical part of cable-supported bridges. Tensile-plate anchorage (TPA) is one of the most commonly used types of cable-girder anchorage joints in steel girder cable-supported bridges. In recent years, it has been proposed by bridge designers to apply TPA to concrete girder cable-supported bridges to form composite cable-girder anchorage joint (CCGAJ). In this paper, the mechanical performance of CCGAJ under tensile force is studied through experimental and numerical analyses. Firstly, the effects of the external prestressing (EP) and the bearing plate (BP) on the mechanical performance of CCGAJ were investigated through three tests. Then, finite element model was established for parametrical study, and was verified by the experimental results. Then, the effects of shear connector forms, EP, BP, vertical rebar rate, and perforated rebar rate on the tensile capacity of CCGAJ were investigated through numerical analyses. The results show that the tensile capacity of CCGAJ depends on the first row of PR. The failure mode of CCGAJ using headed stud connectors is to form a shear failure surface at the end of the studs while the failure mode using PBLs is similar to the bending of a deep girder. Finally, based on the strut-and-tie model (STM), a calculation method for CCGAJ tensile capacity was proposed, which has a high accuracy and can be used to calculate the tensile capacity of CCGAJ.

• Steel and Composite Structures
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• 제45권1호
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• pp.101-118
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• 2022

The seismic performance of the reinforced concrete (RC) special-shaped column to steel beam connections with steel jacket used in the RC column to steel beam fabricated frame structures was investigated in this study. The three full-scale specimens were subjected to cyclic loading. The failure mode, ultimate bearing capacity, shear strength capacity, stiffness degradation, energy dissipation capacity, and strain distribution of the specimens were studied by varying the steel jacket thickness parameters. Test results indicate that the RC special-shaped column to steel beam connection with steel jacket is reliable and has excellent seismic performance. The hysteresis curve is full and has excellent energy dissipation capacity. The thickness of the steel jacket is an important parameter affecting the seismic performance of the proposed connections, and the shear strength capacity, ductility, and initial stiffness of the specimens improve with the increase in the thickness of the steel jacket. The calculation formula for the shear strength capacity of RC special-shaped column to steel beam connections with steel jacket is proposed on the basis of the experimental results and numerical simulation analysis. The theoretical values of the formula are in good agreement with the experimental values.

• 한국지반공학회논문집
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• 제35권12호
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• pp.69-89
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• 2019

사질토를 지나 풍화암에 4D 소켓된 매입 PHC말뚝에 대한 매개변수 수치해석 자료를 분석하여 지지력 표해 및 도해(I)이 제안된 바 있다(Choi et al., 2019a). 본 논문에서는 이를 활용하여 직경의 5% 침하량에서 발현되는 동원지지력을 산정할 수 있는 새로운 산정공식을 제안하였다. 제안식은 두 가지이며, 그 중에서 EQ-G1 제안식은 각각의 상대근입길이(L/D)에서 말뚝직경과 ${\bar{N}}$값(보정 N 값)을 고려하여 각 지지력 성분을 평가하며, 검증 결과는 다음과 같다. RQP는 약 71~94%로 나타났으며, 이는 일반 설계에서 사용하고 있는 지지력 산정공식으로 구한 SRF(26~37%)보다 큰 값을 나타냈다. RQP는 적정 설계의 범위로 분포하였는데, 4개 사례에서는 78, 136, 142, 180%로 나타났다. D_E는 β₁에 따라 달라질 수는 있는데, 본 연구에서는 0.85로 가정하였으므로 D_E는 약 85%로 나타났다. 따라서 본 연구에서 제안한 EQ-G1 제안식을 사용하여 PHC말뚝 몸체의 허용압축하중(P_all)까지 활용할 수 있는 적정설계를 수행할 수 있는 것으로 판단된다. 그리고 EQ-G2-3 제안식은 D, ${\bar{N}}$ 및 L/D를 동시에 고려하여 지지력 성분들을 평가할 수 있으며, 매입 PHC말뚝에서 지반의 압축지지력 산정 시 근사해법으로 활용할 수 있다.

• Steel and Composite Structures
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• 제24권6호
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• pp.679-688
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• 2017

A GFRP-concrete composite bridge deck is presented in this paper. This composite deck is composed of concrete and a GFRP plate and is connected by GFRP perfobond (PBL) shear connectors with penetrating GFRP rebar. There are many outstanding advantages in mechanical behavior, corrosion resistance and durability of this composite deck over conventional reinforced concrete decks. To analyze the shear and flexural performance of this GFRP-concrete composite deck, a static loading experiment was carried out on seven specimens. The failure modes, strain development and ultimate bearing capacity were thoroughly examined. Based on elastic theory and strain-based theory, calculation methods for shear and flexural capacity were put forward and revised. The comparison of tested and theoretical capacity results showed that the proposed methods could effectively predict both the flexural and shear capacity of this composite deck. The ACI 440 methods were relatively conservative in predicting flexural capacity and excessively conservative in predicting shear capacity of this composite deck. The analysis of mechanical behavior and the design method can be used for the design of this composite deck and provides a significant foundation for further research.

• 한국지반공학회논문집
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• 제24권12호
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• pp.13-22
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• 2008

지반조건과 말뚝의 테이퍼각도가 태야퍼말뚝의 지지력에 미치는 영향을 조사하기 위해서 원통형말뚝과 테이퍼각도가 다른 두 개의 메이퍼딸뚝을 이용해서 모형말뚝재하시험을 수행하였다. 시험결과에 띠르면 지반의 평균응력과 상대밀도가 커지면 테이퍼말뚝의 단위 선단지지력은 증가하였고, 말뚝의 테이퍼각도가 커집에 따라 느슨한 지반에서는 단위 선단지지력은 증가하였으나 조밀한 지반에서는 단위 선단지지력이 반대로 감소하였다. 그리고 테이퍼말뚝의 단위 주면마찰력은 지반의 수평 및 연직응력과 상대밀도, 말뚝의 테이퍼각도가 커짐에 따라 증가하는 것으로 나타났다. 한편, 모형말뚝재하시험의 결과에 근거해서 형상계수를 표함한 테이퍼말뚝의 지지력 산정식을 제안하였고, 이 제안식에서는 지반조건과 테이퍼각도가 말뚝의 지지력에 미치는 영향이 고려되였다. 제안한 지지력 산정식에 대한 정확도를 검증하기 위해서 점토질 모래지반에 설치된 중간규모의 원통형말뚝과 테이퍼말뚝에 대한 현장재하시험이 실시되었고, 이때 측정된 지지력이 제안식에서 얻은 예측치와 비교되었다. 그 결과 제안된 지지력 산정식은 테이퍼말뚝의 지지력을 비교적 정확하게 예측하는 것으로 나타났다.

• Computers and Concrete
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• 제31권3호
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• pp.197-206
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• 2023

In this paper, the bending performance of a MSFRHPC (containing steel fiber, polyvinyl alcohol (PVA) fiber, and CW)-reinforced beam was studied for the first time. Introducing a multiscale fiber system increased the first crack load (up to 150%), yield load (up to 50%), and peak load (up to 15%) of reinforced beams. The multiscale fiber system delays cracking of the reinforced beam, reduces crack width of the reinforced beam in normal use, and improves the durability of the beam. Considering yield load and peak load, the reinforcing effect of multiscale fiber on the high-reinforcement ratio beam (1.00%) is better than that on the low-reinforcement ratio beam (0.57%). Introducing fibers slowed the development of cracks in the reinforced beam under bending. With the added hybrid fiber, the deformation concentration of reinforced beams after yield was more significant with concentration in 1 or 2 cracks. A model for predicting the flexural capacity of MSFRHPC-reinforced beams was proposed, considering the action of multiscale hybrid fibers. This research is helpful for structure application of MSFRHPC-containing CW.