• Structural Engineering and Mechanics
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• 제59권4호
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• pp.775-793
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• 2016

This paper presents a numerical method for estimating the curvature, deflection and moment capacity of FRP-reinforced concrete encased steel composite beams (FRP-RCS). A sectional analysis is first carried out to predict the moment-curvature relationship from which beam deflection and moment capacity are then calculated. Comparisons between theoretical and experimental results of tests conducted elsewhere show that the proposed numerical technique can accurately predict moment capacity and deflection of FRP-RCS composite beam. The numerical results also indicated that beam ductility and stiffness are improved when encased steel is added to FRP reinforced concrete beams. ACI, ISIS and Bischoff models for deflection prediction compared well at low load, however, significantly underestimated the experimental results for high load levels.

• Steel and Composite Structures
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• 제23권1호
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• pp.17-29
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• 2017

The seismic performance of steel beam to concrete-encased composite column with unsymmetrical steel section joints is investigated and reported within this paper. Experimental and analytical evaluation were conducted on a total of 8 specimens with T-shaped and L-shaped steel section under lateral cyclic loading and axial compression. The test parameters included concrete strength, stirrup ratio and axial compression ratio. The response of the specimens was presented in terms of their hysterisis loop behavior, stress distribution, joint shear strength, and performance degradation. The experiment indicated good structural behavior and good seismic performance. In addition, a three-dimensional nonlinear finite-element analysis simulating was conducted to simulate their seismic behaviors. The finite-element analysis incorporated both bond-slip relationship and crack interface interaction between steel and concrete. The results were also compared with the test data, and the analytical prediction of joint shear strength was satisfactory for both joints with T-shaped and L-shaped steel section columns. The steel beam to concrete-encased composite column with unsymmetrical steel section joints can develop stable hysteretic response and large energy absorption capacity by providing enough stirrups and decreased spacing of transverse ties in column.

• Steel and Composite Structures
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• 제19권5호
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• pp.1237-1258
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• 2015

This paper proposes a simple inelastic analysis approach to efficiently map out the complete nonlinear post-collapse (strain-softening) response and the maximum load capacity of axially loaded concrete encased steel composite columns (stub and slender). The scheme simultaneously incorporates the influences of difficult instabilizing phenomena such as concrete confinement, initial geometric imperfection, geometric nonlinearity, buckling of reinforcement bars and local buckling of structural steel, on the overall behavior of the composite columns. The proposed numerical method adopts fiber element discretization and an iterative M${\ddot{u}}$ller's algorithm with an additional adaptive technique that robustly yields solution convergence. The accuracy of the proposed analysis scheme is validated through comparisons with various available experimental benchmarks. Finally, a parametric study of various key parameters on the overall behaviors of the composite columns is conducted.

• Steel and Composite Structures
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• 제20권6호
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• pp.1305-1322
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• 2016

This paper presents the results of experimental and numerical model analyses on partially encased composite columns under concentric loads. The main objective of this study is to evaluate the influence of replacing the conventional longitudinal and transverse steel bars by welded wire mesh on the structural behavior of these members under concentric loads. To achieve these goals experimental tests on four specimens of partially encased composite columns submitted to axial loading were performed and the results were promising in terms of replacing the traditional reinforcement by steel meshes. In addition, a numerical FE model was developed using the software DIANA$^{(R)}$ with FX+. The experimental results were used to validate the numerical model. Satisfactory agreement between experimental and numerical results was observed in both capacity and deformability of the composite columns. Despite of the simplifying assumptions of perfect bond between steel and concrete, the numerical model adequately represented the columns behavior. A finite element parametric study was performed and parameters including thickness of the steel profile and the concrete and steel strengths were evaluated. The parametrical study results found no significant changes in the partially encased columns behavior due to variations of the steel profile thickness or yield strength. However, significant changes in the post peak behavior were observed when using high strength concrete and these results suggest a change in the failure mode.

• Steel and Composite Structures
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• 제33권1호
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• pp.67-79
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• 2019

Composite columns made of high strength materials have been used in high-rise construction owing to its excellent structural performance resulting in smaller cross-sectional sizes. However, due to the limited understanding of its structural response, current design codes do not allow the use of high strength materials beyond a certain strength limit. This paper reports additional test data, analytical and numerical studies leading to a new design method to predict the ultimate resistance of composite columns made of high strength steel and high strength concrete. Based on previous study on high strength concrete filled steel tubular members and ongoing work on high strength concrete encased steel columns, this paper provides new findings and presents the feasibility of using high strength steel and high strength concrete for general double symmetric composite columns. A nonlinear finite element model has been developed to capture the composite beam-column behavior. The Eurocode 4 approach of designing composite columns is examined by comparing the test data with results obtained from code's predictions and finite element analysis, from which the validities of the concrete confinement effect and plastic design method are discussed. Eurocode 4 method is found to overestimate the resistance of concrete encased composite columns when ultra-high strength steel is used. Finally, a strain compatibility method is proposed as a modification of existing Eurocode 4 method to give reasonable prediction of the ultimate strength of concrete encased beam-columns with steel strength up to 900 MPa and concrete strength up to 100 MPa.

• 한국강구조학회 논문집
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• 제15권3호
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• pp.251-259
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• 2003

본 논문은 매립형 SRC기둥의 축력과 변형능력과의 관계를 찾아내기 위하여 해석적인 연구를 수행하였다. 해석 모델은 캔틸레버기둥으로 한정하였으며 SRC 기둥의 비탄성 거동에 영향을 미치는 변수들인 철골비, 매립철골형상과 전단스팬과 춤과의 비에 대하여 검토하였다. 일정회전각하에 축력과 반복수평력을 받는 SRC기둥의 안정적 거동을 보장하기 위한 최대한계축력이 있다는 것을 해석결과들은 보여 주고 있다. 반복 횡하중을 받는 기둥이 저항할 수 있는 최대축력은 소요회전각을 보장하는 안정한계축력으로서 정의된다. 해석결과에 따르면 안정한 계축력비는 강재의 강도가 증가함에 따라 콘크리트의 강도가 감소함에 따라 증가하는 것으로 나타났다. 또한 I형 단면이 매립형 철골로 사용될때 철골 단면적이 증가함에 따라 안정한계 축력비는 증가하며, 십자형 단면이 사용되는 경우에는 단면적에 의한 영향이 거의 없었다.

• Steel and Composite Structures
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• 제34권6호
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• pp.909-927
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• 2020

This paper addresses the results of an experimental study involving 10 partially encased composite columns under concentric and eccentric compressive loads. Parameters such as slenderness ratio, ordinary reinforced concrete and fiber reinforced concrete, load eccentricity and bending axis were investigated. The specimens were tested to investigate the effects of replacing the ordinary reinforced concrete by fiber reinforced concrete on the load capacity and behavior of short and slender composite columns. Various characteristics such as load capacity, axial strains behavior, stiffness, strains on steel and concrete and failure mode are discussed. The main conclusions that may be drawn from all the test results is that the behavior and ultimate load are rather sensitive to the slenderness of the columns and to the eccentricity of loading, specially the bending axis. Experimental results also indicate that replacing the ordinary reinforced concrete by steel fiber reinforced concrete has no considerable effects on the load capacity and behavior of the short and slender columns and the proposed replacement presented very good results.

• Steel and Composite Structures
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• 제47권3호
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• pp.423-436
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• 2023

In this research, we tested 10 simply supported concrete-encased composite columns under monotonic eccentric loads and investigated their shear behaviour. The specimens tested were two reinforced concrete specimens, three steel-reinforced concrete (SRC) specimens with an H-shaped steel section (also called a beam section), and five SRC specimens with a cruciform-shaped steel section (also called a column section). The experimental variables included the transverse steel shape's depth and the longitudinal steel flange's width. Experimental observations indicated the following. (1) The ultimate load-carrying capacity was controlled by web compression failure, defined as a situation where the concrete within the diagonal strut's upper end was crushed. (2) The composite effect was strong before the crushing of the concrete outside the steel shape. (3) We adjusted the softened strut-and-tie SRC (SST-SRC) model to yield more accurate strength predictions than those obtained using the strength superposition method. (4) The MSST-SRC model can more reasonably predict shear strength at an initial concrete softening load point. The rationality of the MSST-SRC model was inferred by experimentally observing shear behaviour, including concrete crushing and the point of sharp variation in the shear strain.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2006년도 춘계학술발표회 논문집(I)
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• pp.398-401
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• 2006

This study investigates the behaviour of Hybrid Beam with reinforced concrete encased steel center and reinforced concrete end. Two types of encased steel shape and two sections are examined in this study. Test results showed that H-Hybrid beam is stronger than Honey-comb Hybrid beam, and the behaviour of composite beam embedded steel at the elastic state is same as that of simple beam.

• Steel and Composite Structures
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• 제16권3호
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• pp.305-323
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• 2014

This paper presents numerical simulations of partially encased composite columns (PEC) with equivalent steel sections. The composite section of PEC column consists of thin walled welded H- shaped steel section with transverse links provided at regular intervals between the flanges. Concrete is poured in the space between the flanges and the web plate. Most of the structural analysis and design software do not handle such composite members due to highly nonlinear material behavior of concrete as well as due to the complex interfacial behaviour of steel and concrete. In this paper an attempt has been made to replace the steel concrete composite section by an equivalent steel section which can be easily incorporated in the design and analysis software. The methodology used for the formulation of the equivalent steel section is described briefly in the paper. Finite element analysis is conducted using the equivalent steel section of partially encased composite columns tested under concentric gravity loading. The reference test columns are obtained from the literature, encompassing a variety of geometric and material properties. The finite element simulations of the composite columns with equivalent steel sections are found to predict the experimental behaviour of partially encased composite columns with very good accuracy.