• 한국지반공학회지:지반
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• 제11권2호
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• pp.19-28
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• 1995

소형 압력 토조(small pressure chamber)를 이용하여 포화된 사질토에 타입된 폐단 강관 말뚝의 인발거동 특성을 연구하였다. 소형 압력 토조 시험에서는 인발 하중이 인발변위와 함께 증가하다가 급작스러운 미끄러짐 변위가 발생되는 현상이 2-3회 반복되다가 완전 인발파괴에 이르게 되는데, 이때 첫번째 미끄러짐 변위가 발생하는 하중의 크기를 극한 인발 지지력으로 정의할 수 있다. 또한, 소형 압력 토조 시험에서는 미세한 시험 조건에 의해서도 극한 인발 지지력의 크기가 50% 이상의 오차를 나타낼 수도 있으므로 모형 지반을 형성할 때마다 인발 재하 시험에 의하여 극한 인발 지지력을 결정하여 사용하는 것이 좋을 것으로 판단되며, 이때 1차 인발 시험에 의해 교란된 지반의 상태는 모형 말뚝의 크기에 적합한 타격에너지를 가해주어 회복시킬 수 있다.

• Steel and Composite Structures
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• 제45권5호
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• pp.715-728
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• 2022

Closed steel supports of different shapes are used in mining and underground constructions. The supports are prefabricated from rolled, usually robust, steel profiles. The load carrying capacity of a support is considerably influenced by the active loading and passive forces. The passive forces are induced by interactions between the support and the surrounding rock mass. The analysis herein comprises three parts: The first part consists of structural geometry processing. The second part involves finding the numerical solution of a statically indeterminate structure for a specified load. The third part is calculation of the load carrying capacity and the components of internal forces and deformations. For this, the force method and numerical integration are used. The Winkler model is applied when the support interacts with the surrounding environment. The load carrying capacity is limited by the slip resistance of the connected parts and it is limited by reaching the ultimate state of the profile. This paper serves as a comprehensive reference for the determination of the load carrying capacity of closed steel supports and includes stepwise derivations of the governing formulas.

• 한국지반공학회논문집
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• 제19권6호
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• pp.227-243
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• 2003

강관말뚝의 속채움 콘크리트 B방법에서 미끌림방지턱의 구조적인 특성을 알아보기 위하여, 강관말뚝머리의 내부에 미끌림방지턱을 설치하지 않은 시험체와 2단의 곡률 강편 미끌림방지턱을 강관말뚝내부에 용접한 시험체(시방서 방법), 그리고 미끌림방지턱을 다수의 곡률 강편과 고장력볼트로 체결한 시험체(개발형 방법)에 대하여 실물크기 인발 및 압발 실험을 수행하였다. 그 결과, 미끌림방지턱이 없는 시험체는 최대인발하중 15.6tonf에서, 최대압발하중 27.57tonf에서 콘크리트의 화학적 부착파괴가 발생하였다. 그리고 미끌림방지턱이 있는 시방서 방법과 개발형 방법의 시험체는 없는 시험체보다 최대인발하중의 약 8.9배와 최대압발하중의 6.2배 크게 나타났다. 또한 시방서 방법과 개발형 방법의 하단 미끌림방지턱에 대한 하중분담비율은 거의 동일한 거동을 보인 반면에, 상단 미끌림방지턱은 시방서방법보다 개발형 방법의 하중분담비율이 크게 기여하였다. 그리고 시방서 방법과 개발형 방법의 미끌림방지턱 형상에 의한 합성작용과 구조성능은 거의 동일하였다.

• Steel and Composite Structures
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• 제48권3호
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• pp.251-262
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• 2023

There are many examples of steel structures subjected to severe environmental conditions with bolted connections directly exposed to extreme climatic agents such as freeze-thaw cycles or low temperatures. Some examples are: steel bridges, mining transfer towers, wind towers... These service conditions neither are included in Eurocode 3 or EN1090-2, nor there are references in other international standards. In this experimental research, 46 specimens of non-slip joints with HV M20 bolts and four different types of contact surfaces have been studied. Half of the specimens were subjected to fourteen twelve-hours freeze-thaw cycles, with periodic immersion in water and temperature oscillation. Subsequently, half of the connections were subjected to a slip test under monotonic load at temperature of -20 ± 0.5 ℃ and the other half at room temperature. The results were compared with others equal joints not subjected to freeze-thaw cycles and kept at room temperature for the same time. This finally resulted in 4 sets of joints by combining the freeze-thaw degradation or not with the low-temperature conditions or not in the slip testing. Therefore, a total of 16 different conditions were studied by also considering 4 different contact surfaces between the joined plates in each set. The results obtained show influence of environmental conditions on the slip resistant capacity of these joints.

• Steel and Composite Structures
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• 제20권1호
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• pp.71-89
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• 2016

In steel and concrete composite girders, the load transfer between the steel beam and the concrete slab is commonly ensured by installing shear connectors. In this paper, to investigate the nonlinear behavior of perfobond connectors, a total of 60 push-out specimens were fabricated and tested with the variables for the hole diameter, the concrete strength, the thickness of concrete slab, the diameter, strength and existence of perforating rebar, the thickness, height and distance of perfobond ribs. The failure mode and the load-slip behavior of perfobond connectors were obtained. A theoretical model was put forward to express the load-slip relationship. Analytical formulas of shear capacity and peak slip were also proposed considering the interaction between the concrete dowel and the perforating rebar. The calculation results of the proposals agreed well with the experimental values.

• 한국안전학회지
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• 제27권6호
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• pp.122-126
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• 2012

Steel lining board usually is used as a floor on the temporary steel bridges. It also is installed in the subway construction site. However, in particular in subway construction, renovations and site of old bridges, these steel lining board structures have a problem such as noise, accidents and slip hazards. So steel composite lining board is being developed to solve this problem. Steel composite lining board consists of compressive concrete showing excellent performance in slip, durability, resistance and noise, lower tensile and shear steel showing high safety, effective and superior workability in many respects. Steel composite lining board structure gradually is used in many construction sites, because it has a high quality such as durability, little noise and slip. In this study, flexural tests of steel composite lining board in accordance with welding patterns were conducted to compare the performance of the structure.

• Earthquakes and Structures
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• 제24권5호
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• pp.365-375
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• 2023

Energy dissipation systems increase the energy dissipation capacity of buildings considerably. In this study, the effect of dampers on a typical 10-storey reinforced concrete structure with a ductile moment-resisting frame was investigated. In this context, 5 different models were created according to the calculation of the slip load and the positions of the dampers in the structure. Nonlinear time-history analyzes using 11 different earthquake acceleration records were performed on the models using the ETABS program. As a result of the analyses, storey displacements, energy dissipation ratios, drift ratios, storey accelerations, storey shears, and hysteretic curves of the dampers on the first and last storey and overturning moments are presented. In the study, it was determined that friction dampers increased the energy dissipation capacities of all models. In addition, it has been determined that positioning the dampers in the outer region of the structures and taking the base shear as a basis in the slip load calculation will be more effective.

• Structural Engineering and Mechanics
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• 제32권2호
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• pp.251-267
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• 2009

Reinforced concrete (RC) structures consist of two different materials: concrete and steel bar. The stress transfer behaviour between the two materials through bond plays an important role in the load-carrying capacity of RC structures, especially when they subject to lateral load such as blast and seismic load. Therefore, bond and slip between concrete and reinforcement bar will affect the response of RC structures under such loads. However, in most numerical analyses of blast-induced structural responses, the perfect bond between concrete and steel bar is often assumed. The main reason is that it is very difficult to model bond slip in the commercial finite element software, especially in hydrodynamic codes. In the present study, a one-dimensional slide line contact model in LS-DYNA for modeling sliding of rebar along a string of concrete nodes is creatively used to model the bond slip between concrete and steel bars in RC structures. In order to model the bond slip accurately, a new approach to define the parameters of the one-dimensional slide line model from common pullout test data is proposed. Reliability and accuracy of the proposed approach and the one-dimensional slide line in modelling the bond slip between concrete and steel bar are demonstrated through comparison of numerical results and experimental data. A case study is then carried out to investigate the bond slip effect on numerical analysis of blast-induced responses of a RC column. Parametric studies are also conducted to investigate the effect of bond shear modulus, maximum elastic slip strain, and damage curve exponential coefficient on blast-induced response of RC columns. Finally, recommendations are given for modelling the bond slip in numerical analysis of blast-induced responses of RC columns.

• Steel and Composite Structures
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• 제42권3호
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• pp.407-426
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• 2022

Superior to traditional welded studs, high strength friction-grip bolted shear connectors facilitate the assembling and demounting of the composite members, which maximizes the potential for efficiency in the construction and retrofitting of new and old structures respectively. Hence, it is necessary to investigate the structural properties of high strength friction-grip bolts used in steel concrete composite beams. By means of push-out tests, an experimental study was conducted on post-installed high strength friction-grip bolts, considering the effects of different bolt size, concrete strength, bolt tensile strength and bolt pretension. The test results showed that bolt shear fracture was the dominant failure mode of all specimens. Based on the load-slip curves, uplifting curves and bolt tensile force curves between the precast concrete slab and steel beam obtained by push-out tests, the anti-slip performance of steel-concrete interface and shear behavior of bolt shank were studied, including the quantitative analysis of anti-slip load, and anti-slip stiffness, frictional coefficient, shear stiffness of bolt shank and ultimate shear capacity. Meanwhile, the interfacial anti-slip stiffness and shear stiffness of bolt shank were defined reasonably. In addition, a total of 56 push-out finite element models verified by the experimental results were also developed, and used to conduct parametric analyses for investigating the shear behavior of high-strength bolted shear connectors in steel-concrete composite beams. Finally, on ground of the test results and finite element simulation analysis, a new design formula for predicting shear capacity was proposed by nonlinear fitting, considering the bolt diameter, concrete strength and bolt tensile strength. Comparison of the calculated value from proposed formula and test results given in the relevant references indicated that the proposed formulas can give a reasonable prediction.

• International Journal of Concrete Structures and Materials
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• 제18권1E호
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• pp.29-34
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• 2006

Elastic modulus, tensile and bond capacities are important factors for developing an effective reinforcing action of a flexural member as a reinforcing material for concrete structures. Reinforcement must have enough bond capacity to prevent the relative slip between concrete and reinforcement. This paper presents an experimental study to clarify the bond capacity of prestressed carbon fiber reinforced polymer(CFRP) rod manufactured by an automatic assembly robot. The bond characteristics of CFRP rods with different pitch of helical wrapping were analyzed experimentally. As the result, all types of CFRP rods show a high initial stiffness and good ductility. The mechanical properties of helical wrapping of the CFRP rods have an important effect on the bond of these rods to concrete after the bond stress reached the yield point. The stress-slip relationship analyzed from the pull-out test of embedded cables within concrete was linear up to maximum bond capacity. The deformation within the range of maximum force seems very low and was reached after approximately 1 mm. The average bond capacity of CF20, CF30 and CF40 was about 12.06 MPa, 12.68 MPa and 12.30 MPa, respectively. It was found that helical wrapping was sufficient to yield bond strengths comparable to that of steel bars.