• Geomechanics and Engineering
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• 제34권1호
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• pp.17-27
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• 2023

Taking a subway shield tunnel in a certain section of Zhengzhou Metro Line 5 as an example, the field tests of shield cutting cement-soil monopile composite foundation were carried out. The load and internal force of the tunnel lining under the action of composite foundation were tested on-site and the distribution characteristics and variation laws of earth pressure around the tunnel under the load holding state of the composite foundation were analyzed. Five different load combinations (i.e., overburden load theory + q₀, Terzaghi's theory + q₀, Bierbaumer's theory + q₀, Xie's theory + q₀, and the proposed method (the combination of compound weight method and Terzaghi's theory) + q₀) were used to calculate the internal force of the tunnel structure and the obtained results were compared with the measured internal force results. The action mode of earth pressure on the tunnel lining structure was evaluated. Research results show that the earth pressure obtained by the calculation method proposed in this paper was more consistent with the measured value and the deviation between the two was within 5%. The distribution of the calculated internal force of the tunnel structure was more in line with the distribution law of field test data and the deviation between the calculated and measured values was small. This effectively verified the rationality and applicability of the proposed calculation method. Research results provided references for the design and evaluation of shield tunnels under the action of composite foundations.

• Structural Engineering and Mechanics
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• 제21권6호
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• pp.659-676
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• 2005

The novel form of composite walling system consists of two skins of profiled steel sheeting with an in-fill of concrete. The behaviour of such walling under in-plane shear is important in order to utilise this system as shear elements in a steel framed building. Steel sheet-concrete interface governs composite action, overall behaviour and failure modes of such walls. This paper describes the finite element (FE) modelling of the shear behaviour of walls with particular emphasis on the simulation of steel-concrete interface. The modelling of complex non-linear steel-concrete interaction in composite walls is conducted by using different FE models. Four FE models are developed and characterized by their approaches to simulate steel-concrete interface behaviour allowing either full or partial composite action. Non-linear interface or joint elements are introduced between steel and concrete to simulate partial composite action that allows steel-concrete in-plane slip or out of plane separation. The properties of such interface/joint elements are optimised through extensive parametric FE analysis using experimental results to achieve reliable and accurate simulation of actual steel-concrete interaction in a wall. The performance of developed FE models is validated through small-scale model tests. FE models are found to simulate strength, stiffness and strain characteristics reasonably well. The performance of a model with joint elements connecting steel and concrete layers is found better than full composite (without interface or joint elements) and other models with interface elements. The proposed FE model can be used to simulate the shear behaviour of composite walls in practical situation.

• 복합신소재구조학회 논문집
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• 제5권2호
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• pp.27-32
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• 2014

Since the collapse of historical masonry structures in Europe in the late 1990's, the interests in understanding the long-term effect of masonry under sustained compressive stresses have increased. That requires combining the significance of time-dependent effects of creep with the effect of damage due to overstress to realize the evolution of cracks and then failure in masonry. Meanwhile, composite analysis of masonry columns was proven effective for realizing ultimate strength capacity of masonry column. In this study, a simplified mechanical model with step-by-step in time analysis was proposed to incorporate the interaction of damage and creep to estimate the maximum stress occurred in masonry. It was examined that the interaction of creep and damage in masonry can accelerate the failure of masonry.

• Steel and Composite Structures
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• 제17권6호
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• pp.907-927
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• 2014

Ultra-lightweight cement composite (ULCC) with a compressive strength of 60 MPa and density of $1450kg/m^3$ has been developed and used in the steel-concrete-steel (SCS) sandwich structures. ULCC was adopted as the core material in the SCS sandwich composite beams to reduce the overall structural weight. Headed shear studs working in pairs with overlapped lengths were used to achieve composite action between the core material and steel face plates. Nine quasi-static tests on this type of SCS sandwich composite beams were carried out to evaluate their ultimate strength performances. Different parameters influencing the ultimate strength of the SCS sandwich composite beams were studied and discussed. Design equations were developed to predict the ultimate resistance of the cross section due to pure bending, pure shear and combined action between shear and moment. Effective stiffness of the sandwich composite beam section is also derived to predict the elastic deflection under service load. Finally, the design equations were validated by the test results.

• The Journal of Korean Physical Therapy
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• 제32권2호
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• pp.65-69
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• 2020

Purpose: This study examined the effects of action-observation training using the Y-Balance on the balance ability of young adults. Methods: Thirty-four healthy adults were randomized into an action-observation group (n=17) or a control group (n=17). All subjects performed the Y-Balance test before and after watching the video. The action observation group watched a video of someone performing a Y-Balance test, and the control group watched a video of scenery unrelated to the training. The subjects were measured through a Y-Balance test for both the length of the legs extended in three directions and the Y-balance composite score. Results: A significant difference in the Y-balance composite score was observed between the two groups. A part of the direction of the extended leg in the action observation group was increased significantly (posteromedial direction of the right leg, posterolateral direction of the right leg, posteromedial direction of left leg) compared to the control group. Conclusion: These results suggest that action observation training only could help improve balance.

• Steel and Composite Structures
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• 제23권2호
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• pp.229-238
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• 2017

This paper presents a combined numerical and theoretical study on the composite action between steel and concrete of circular steel tube confined concrete (STCC) stub columns under axial compressive loading with a full theoretical elasto-plastic model and finite element (FE) model in comparison with experimental results. Based on continuum mechanics, the elasto-plastic model for STCC stub columns was established and the analysis was realized by a FORTRAN program and the three dimensional FE model was developed using ABAQUS. The steel ratio of the circular STCC columns were defined in range of 0.5% to 2% to analyze the composite action between steel tube and concrete, and make a further study on the advantages of the circular STCC columns. By comparing the results using the elasto-plastic methods with the parametric analysis result of FE model, the appropriate friction coefficient between the steel tube and core concrete was defined as 0.4 to 0.6. Based on ultimate balance theory, the formula of ultimate load capacity applying to the circular STCC stub columns was developed.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1999년도 학회창립 10주년 기념 1999년도 가을 학술발표회 논문집
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• pp.571-574
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• 1999

Due to many advantages of advanced composite material, research on the composite compression member is initiated. In this paper structural characteristics of concrete filled glass fiber reinforced composite tubular member si studied. Experimental results shows that strength and ductility of composite compression member is considerably increased due to concrete confinement action of composite surface. Thus it can be anticipated that increased strength of concrete will be incorporated in the design of composite compression member.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 1999년도 추계학술발표대회 논문집
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• pp.183-188
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• 1999

Due to many advantages of advanced composite materials, research on the application of composites to the construction industry is initiated. In this paper, fabrication methods efficient for infrastructures and application examples of each method are discussed. It also presents the structural characteristics of concrete filled glass fiber reinforced composite tubular member. Experimental results shows that strength and ductility of composite compression member is considerably increased due to concrete confinement action of composite surface.

• Steel and Composite Structures
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• 제35권3호
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• pp.371-384
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• 2020

The steel-concrete double composite girder in the negative flexural region combines an additional concrete slab to the steel bottom flange to prevent the local steel buckling, however, the additional concrete slab may lower down the neutral axis of the composite section, which is a sensitive factor to the tensile stress restraint on the concrete deck. This is actually of great importance to the structural rationality and durability, but has not been investigated in detail yet. In this case, a series of 5.5 m-long composite girder specimens were tested by negative bending, among which the bottom slab configuration and the longitudinal reinforcement ratio in the concrete deck were the parameters. Furthermore, an analytical study concerning about the influence of bottom concrete slab thickness on the cracking and sectional bending-carrying capacity were carried out. The test results showed that the additional concrete at the bottom improved the composite sectional bending stiffness and bending-carrying capacity, whereas its effect on the concrete crack distribution was not obvious. According to the analytical study, the additional concrete slab at the bottom with an equivalent thickness to the concrete deck slab may provide the best contributions to the improvements of crack initiation bending moment and the sectional bending-carrying capacity. This can be applied for the design practice.

• 콘크리트학회논문집
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• 제17권3호
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• pp.393-400
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• 2005

강재 매입형 합성기둥 구조는 주로 건물구조와 교량의 교각구조에 적용되어 왔고, 최근에는 교량의 교각구조에 적용하는 예가 늘어나고 있는 실정이다. 교각은 건물의 기둥에 비해 상당히 큰 규모의 구조물이기 때문에 강재비를 적절한 수준으로 유도하면서 의도하는 성능을 만족하는 단면을 설계해야 한다. 그러나 합성구조의 기본원리가 구조물을 구성하는 구조재료의 일체화된 거동에 근거함으론 강재 매입형 합성기둥 구조의 적용에 앞서, 먼저 콘크리트와 강재 단면의 합성 작용에 대한 명확한 정의가 필요하다. 일반적으로 강재 매입형 합성구조는 부착과 마찰에 의해서 합성작용을 확보한다고 가정하고 설계하는데, 콘크리트 단면 강재 단면 그리고 합성 단면으로 각각 다를 경우, 거동의 차이를 가져올 수 있기 때문에 적절한 합성작용을 위한 규정이 요구된다. 이 논문에서는 횡방향 철근에 의한 콘크리트의 구속 효과, H형 강재 복부의 천공에 의한 기계적 맞물림 그리고 전단 연결재에 의한 영향을 고려하여 실험을 수행하였다. 실험을 통해 계산된 값보다 큰 부착 강도를 얻을 수 있었다. 구속효과, 기계적 맞물림 그리고 전단 연결재를 통해 전단 강도의 증가를 유도할 수 있었고, 이는 강재 매입형 합성 기둥에서 합성 작용을 확보하는데 효과적으로 이용될 수 있다.