• Structural Engineering and Mechanics
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• 제67권1호
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• pp.79-85
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• 2018

Topology optimization of steel and concrete composite based on truss-like material model is studied in this paper. First, the initial design domain is filled with concrete, and the steel is distributed in it. The problem of topology optimization is to minimize the volume of steel material and solved by full stress method. Then the optimized steel and concrete composite truss-like continuum is obtained. Finally, the distribution of steel material is determined based on the optimized truss-like continuum. Several numerical results indicate the numerical instability and rough boundary are settled. And more details of manufacture and construction can be presented based on the truss-like material model. Hence, the truss-like material model of steel and concrete is efficient to establish the distribution of steel material in concrete.

• Steel and Composite Structures
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• 제32권4호
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• pp.443-454
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• 2019

With the aim to put forward the analytical model for calculating the shear capacity of precast steel reinforced concrete (PSRC) beams, a static test on two full-scale PSRC specimens was conducted under four-point loading, and the failure modes and strain developments of the specimens were critically investigated. Based on the test results, a modified truss-arch model was proposed to analyze the shear mechanisms of PSRC and cast-in-place SRC beams. In the proposed model, the overall shear capacity of PSRC and cast-in-place SRC beams can be obtained by combining the shear capacity of encased steel shape with web concrete determined by modified Nakamura and Narita model and the shear capacity of reinforced concrete part determined by compatible truss-arch model which can consider both the contributions of concrete and stirrups to shear capacity in the truss action as well as the contribution of arch action through compatibility of deformation. Finally, the proposed model is compared with other models from JGJ 138 and AISC 360 using the available SRC beam test data consisting of 75 shear-critical PSRC and SRC beams. The results indicate that the proposed model can improve the accuracy of shear capacity predictions for shear-critical PSRC and cast-in-place SRC beams, and relatively conservative results can be obtained by the models from JGJ 138 and AISC 360.

• 대한토목학회논문집
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• 제32권4A호
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• pp.237-244
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• 2012

콘크리트는 재료적으로 인장에 취약하고 변형에 취성이 크다는 태생적 단점을 갖고 있다. 콘크리트 조직에 인장에 강한 작은 섬유를 혼합한 섬유보강콘크리트는 이러한 취약점을 보완할 수 있는 좋은 방법으로 간주되었으며, 많은 종류의 섬유재료와 방법들이 제안되었다. 그러나 이 섬유보강콘크리트에도 아직까지 해결하지 못한 문제로서 균질한 배합이 힘들고 높은 체적비를 갖는 섬유 혼입의 어려움 등이 있다. 최근에 새로운 개념의 규칙적 다공질 금속(periodic cellular metal)이 개발되어 기계 분야에 많이 적용되고 있는 철선으로 직조된 카고메 트러스가 있다. 이 논문은 기존 강섬유보강콘크리트의 현실적 문제점을 해결하기 위한 방법의 일환으로 카고메 트러스의 적용 가능성을 검토하기 위한 기초 실험 연구 결과를 정리한 것이다. 3종류의 카고메 트러스로 보강된 실험체와 동일한 제원의 수직스터럽으로 보강된 보 실험 결과와 비교하였다. 그 결과, 카고메 트러스 보강 실험체에서는 강도와 연성이 보통 스터럽 보강 보 보다 더 우수한 결과를 나타냈으며, 복부 보강재로서 우수한 기능을 할 수 있는 것으로 판명되었다.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2005년도 봄학술 발표회 논문집(I)
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• pp.367-370
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• 2005

This study is to propose a truss model which is able to reasonably predict the shear strength of reinforced concrete (RC) members with high-strength materials. The shear strengths of 107 RC test beams with high-strength steel bars reported in the technical literatures were compared to those obtained from proposed model, TATM, and existing truss models. The shear strength of reinforced concrete beams obtained from test was better predicted by TATM than other truss models. Also, the theoretical results by TATM were almost constant regardless of yield strengths and steel ratios of tension and shear reinforcements.

• 콘크리트학회논문집
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• 제12권6호
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• pp.57-66
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• 2000

The truss analogy for the analysis of beam-columns subjected of shear and flexure is limited by the contribution of transverse and longitudinal steel and diagonal concrete compression struts. However, it should be noted that even though the behavior of reinforced concrete beam-columns after cracking can be modeled with the truss analogy, they are not perfect trusses but still structural elements with a measure of continuity provided by a diagonal tension field. The mere notion of compression field denotes that there should be some tension field coexisting perpendicularly to it. The compression field is assumed to form parallel to the crack plane that forms under combined flexure and shear. Therefore, the concrete tension field may be defined as a mechanism existing across the crack and resisting crack opening. In this paper, the effect of concrete tensile properties on the shear strength and stiffness of reinforced concrete beam-columns is discussed using the Gauss two-point truss model. The theoretical predictions are validated against the experimental observations. Although the agreement is not perfect, the comparison shows the correct trend in degradation as the inelasticity increases.

• Steel and Composite Structures
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• 제43권2호
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• pp.139-152
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• 2022

Steel-reinforced concrete (SRC) L-shaped column is the vertical load-bearing member with high spatial adaptability. The seismic behavior of SRC L-shaped column is complex because of their irregular cross sections. In this study, the hysteretic performance of six steel truss reinforced concrete L-shaped columns specimens under the combined loading of compression, bending, shear, and torsion was tested. There were two parameters, i.e., the moment ratio of torsion to bending (γ) and the aspect ratio (column length-to-depth ratio (φ)). The failure process, torsion-displacement hysteresis curves, and bending-displacement hysteresis curves of specimens were obtained, and the failure patterns, hysteresis curves, rigidity degradation, ductility, and energy dissipation were analyzed. The experimental research indicates that the failure mode of the specimen changes from bending failure to bending-shear failure and finally bending-torsion failure with the increase of γ. The torsion-displacement hysteresis curves were pinched in the middle, formed a slip platform, and the phenomenon of "load drop" occurred after the peak load. The bending-displacement hysteresis curves were plump, which shows that the bending capacity of the specimen is better than torsion capacity. The results show that the steel truss reinforced concrete L-shaped columns have good collapse resistance, and the ultimate interstory drift ratio more than that of the Chinese Code of Seismic Design of Building (GB50011-2014), which is sufficient. The average value of displacement ductility coefficient is larger than rotation angle ductility coefficient, indicating that the specimen has a better bending deformation resistance. The specimen that has a more regular section with a small φ has better potential to bear bending moment and torsion evenly and consume more energy under a combined action.

• 한국공간구조학회논문집
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• 제21권1호
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• pp.71-78
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• 2021

The U-flanged truss hybrid beam is a new composite beam made by pouring concrete into the U-flanged truss beam. In this study, an experimental study was performed to verify the shear capacity of U-flanged truss hybrid beams with the newly developed end reinforcement details. For all specimens, the maximum shear strength was determined by shear failure of concrete in the loading point The detail reinforced with stirrups at the end zone can exhibit the greatest shear strength, but the method of reinforcing the end zone using vertical steel plates, which is a relatively easy method to manufacture, is considered to be the most effective detail in terms of shear strength and ductility. Also, in the case of U-flanged truss hybrid beams reinforced with vertical steel plates at the end zone, the shear strength can be evaluated on the safety side by using the Korea Design Standard formula.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2001년도 가을 학술발표회 논문집
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• pp.1103-1108
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• 2001

ACI 318-99 predicts the torsional moment of reinforced concrete members by assuming that the angle of diagonal compressive concrete is equal to 45 degree. However, this angle depends on the difference of longitudinal and transverse steel ratios. This paper compares the torsional moments calculated by ACI 318-99 code and a truss model considering compatibility of strains. The comparison indicated that the torsion equation in ACI code underestimated the real torsional moment of reinforced concrete beam in which the ratio of longitudinal reinforcement was larger than that of transverse reinforcement.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1999년도 봄 학술발표회 논문집(I)
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• pp.585-590
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• 1999

There is still a lack of knowledge and modelling relating to shear behaviour in reinforced concrete beams. The reason is that shear loading leads to complicated physical mecanisms, such as interlock action, dowel action, etc. Therefore, It is difficult that we make the ideal model of shear behaviour, while Truss model theory has been made good use of shear design because of simplicity and reasonableness. In this study, 6 T-type reinforced concrete beams were designed and made based on the two truss models, i.e, the plasticity truss model and the compatibility truss model, to observe shear strength of concrete and stress distribution of stirrups. 6 beams test pieces were tested with the following testing parameters. 1) specified concrete strength ; 270kg/$\textrm{cm}^2$, 400kg/$\textrm{cm}^2$ 2) with and without the steel fiber.

• Steel and Composite Structures
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• 제26권5호
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• pp.635-647
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• 2018

In order to improve the efficiency of the Reinforced Concrete, RC, structures against progressive collapse, this paper proposes a procedure using alternate path and specific local resistance method to resist progressive collapse in intermediate RC frame structures. Cap truss consists of multiple trusses above a suddenly removed structural element to restrain excessive collapse and provide an alternate path. Steel strut is used as a brace to resist compressive axial forces. It is similar to knee braces in the geometry, responsible for enhancing ductility and preventing shear force localization around the column. In this paper, column removals in the critical position at the first story of two 5 and 10-story regular buildings strengthened using steel strut or cap truss are studied. Based on nonlinear dynamic analysis results, steel strut can only decrease vertical displacement due to sudden removal of the column at the first story about 23%. Cap truss can reduce the average vertical displacement and column axial force transferred to adjacent columns for the studied buildings about 56% and 61%, respectively due to sudden removal of the column. In other words, using cap truss, the axial force in the removed column transfers through an alternate path to adjacent columns to prevent local or general failure or to delay the progressive collapse occurrence.