• Steel and Composite Structures
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• v.25 no.5
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• pp.593-601
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• 2017

Carbon Fiber Reinforced Polymer (CFRP) is one of the materials used to strengthen steel structures. Most studies on strengthening steel structures have been done on steel beams and steel columns. No independent study, to the researcher's knowledge, has studied the effect of CFRP strengthening on steel beam-columns, and it seems that there is a lack of understanding on behavior of CFRP strengthening on steel beam-columns. However, this study explored the use of adhesively bonded CFRP flexible sheets on retrofitting square hollow section (SHS) steel beam-columns, using numerical investigations. Finite Element Method (FEM) was employed for modeling. To determine the ultimate load of SHS steel beam-columns, ten specimens, eight of which were strengthened with the different coverage length and with one and two CFRP layers, with two types of section (Type A and B) were analyzed. ANSYS was used to analyze the SHS steel beam-columns. The results showed that the CFRP composite had no similar effect on the slender and stocky SHS steel beam-columns. The results also showed that the coverage length, the number of layers, and the location of CFRP composites were effective in increasing the ultimate load of the SHS steel beam-columns.

• Steel and Composite Structures
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• v.9 no.1
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• pp.19-38
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• 2009

The present paper provides test data to evaluate the seismic performance of recycled aggregate concrete (RAC) filled steel square hollow section (SHS) beam-columns. Fifteen specimens, including 12 RAC filled steel tubular (RACFST) columns and 3 reference conventional concrete filled steel tubular (CFST) columns, were tested under reversed cyclic flexural loading while subjected to constant axially compressive load. The test parameters include: (1) axial load level (n), from 0.05 to 0.47; and (2) recycled coarse aggregate replacement ratio (r), from 0 to 50%. It was found that, generally, the seismic performance of RACFST columns was similar to that of the reference conventional CFST columns, and RACFST columns exhibited high levels of bearing capacity and ductility. Comparisons are made with predicted RACFST beam-column bearing capacities and flexural stiffness using current design codes. A theoretical model for conventional CFST beam-columns is employed in this paper for square RACFST beam-columns. The predicted load versus deformation hysteretic curves are found to exhibit satisfactory agreement with test results.

• Steel and Composite Structures
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• v.4 no.3
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• pp.169-188
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• 2004

A mechanics model is developed in this paper for concrete-filled steel CHS (circular hollow section) beam-columns. A unified theory is described where a confinement factor (${\xi}$) is introduced to describe the composite action between the steel tube and the filled concrete. The predicted load versus deformation relationship is in good agreement with test results. The theoretical model was used to investigate the influence of important parameters that determine the ultimate strength of concrete-filled steel CHS beam-columns. The parametric and experimental studies provide information for the development of formulas for the calculation of the ultimate strength of the composite beam-columns. Comparisons are made with predicted beam-columns strengths using the existing codes, such as LRFD-AISC-1999, AIJ-1997, BS5400-1979 and EC4-1994.

• Steel and Composite Structures
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• v.18 no.1
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• pp.213-233
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• 2015

A nonlinear finite element analysis (FEA) model is presented for simulating the behaviour of recycled aggregate concrete-filled steel tube (RACFST) beam-columns subjected to constant axial compressive load and cyclically increasing flexural loading. The FEA model was developed based on ABAQUS software package and a displacement-based approach was used. The proposed engineering stress versus engineering strain relationship of core concrete with the effect of recycled coarse aggregate (RCA) replacement ratio was adopted in the FEA model. The predicted results of the FEA model were compared with the experimental results of several RACFST as well as the corresponding concrete-filled steel tube (CFST) beam-columns under cyclic loading reported in the literature. The comparison results indicated that the proposed FEA model was capable of predicting the load versus deformation relationship, lateral bearing capacity and failure pattern of RACFST beam-columns with an acceptable accuracy. A parametric study was further carried out to investigate the effect of typical parameters on the mechanism of RACFST beam-columns subjected to cyclic loading.

• Journal of Korean Society of Steel Construction
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• v.17 no.1 s.74
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• pp.73-82
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• 2005

The objective of this study is to investigate the maximum strength of stainless steel rectangular hollow section columns and beam-columns by using numerical analysis. Stress-strain relationships are modeled based on coupon tests results, and their influences on the maximum strength of columns and beam-columns are discussed. The analysis results are compared with the formula for the limit state design code of steel structures. It is ascertained that the design code for the stainless steel is needed to use stainless steel for the members of architectural structures.

• Architectural research
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• v.3 no.1
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• pp.61-70
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• 2001

The paper is intended to propose design strength of slender steel reinforced beam-columns by using the modified superposed method. The design of composite members is carried out by a superposed strength method in AIJ (Architectural Institute of Japan) design method. The bearing capacities of the steel part and the concrete part have to be determined separately and then added to a combined capacity. Authors have proposed a new superposed method in a modified form for the slender composite beam-columns and reinforced column. The modified superposed method is adopted for the slender steel reinforced beam-columns. Validation of the modified superposed method is undertaken by comparison with analytical results calculated assuming a sine curve deflected shape of the beam-columns, and with the test results conducted in Japan.

• Steel and Composite Structures
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• v.10 no.2
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• pp.109-128
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• 2010

The expediency of using tubular composite steel and concrete columns of annular cross-sections in construction is discussed. The new type space framework with tubular composite columns of multi-storey buildings and its rigid beam-column joints are demonstrated. The features of interaction between the circular steel tube and spun concrete stress-strain states during the concentrical and eccentrical loading of tubular composite members are considered. The modeling of the bearing capacity of beam-columns of composite annular cross-sections is based on the concepts of bending with a concentrical force and compression with a bending moment. The comparison of modeling results for the composite cross-sections of beam-columns is analysed. The expediency of using these concepts for the limit state verification of beam-columns in the methods of the partial safety factors design (PSFD) legitimated in Europe and the load and resistance factors design (LRFD) used in other countries is presented and illustrated by a numerical example.

• Proceedings of the Korea Concrete Institute Conference
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• 2001.11a
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• pp.477-482
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• 2001

This paper is to study the effect of longitudinal reinforcement ratios and axial deformation on the frame analysis in reinforced concrete(RC) columns and to investigate the effect of confined concrete core, the length-width ratio and longitudinal steel ratios on frame analysis in Concrete-Filled steel Tubular(CFT) columns. An equation if derived to evaluate the modulus of elasticity for core concrete. The 34 reference data have been collected for the purpose and are processed by the mean of a multiple regression analysis technique. The equation and longitudinal reinforcement ratios was applied to RC columns for structural analysis. Then, the difference of beam moment was identified. In general, the results of analysis was indicated reasonable differences in beam moment, in case of longitudinal reinforcement ratios applied to RC columns when compared with the plain concrete columns. In CFT columns the equation was also applied in order to the effect of confined concrete core on structural analysis. Beam moment was increased as volumetric ratio of lateral steel was decreased. The effect of longitudinal steel ratios was investigated in CFT columns and was confirmed beam moment variety. The result was appeared reasonable difference in beam moment as longitudinal steel was increased.

• Steel and Composite Structures
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• v.23 no.4
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• pp.399-408
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• 2017

This paper experimentally studies the cyclic behavior of hybrid connections between steel coupling beams and concrete shear walls with embedded steel columns. Four beam-to-wall connection specimens with short and long embedded steel columns are tested under monotonic and cyclic loads, respectively. The influence of embedment length of columns on the failure mode and performance of connections is investigated. The results show that the length of embedded steel columns has significant effect on the failure mode of connections. A connection with a long embedded column has a better stiffness, load-bearing capacity and ductility than that of a short embedded column. The former fails due to the shear yielding of column web in the joint panel, while failure of the latter is initiated by the yielding of horizontal reinforcement in the wall due to the rigid rotation of the column. It is recommended that embedded steel columns should be placed along the entire height of shear walls to facilitate construction and enhance the ductility.

• Steel and Composite Structures
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• v.8 no.4
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• pp.329-342
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• 2008

The strengthening of reinforced concrete (RC) columns by steel angles and strips (steel cage) is one of various techniques available to increase ultimate column load. Different authors have shown the influence of the beam-column joint on the behaviour of columns strengthened by steel cages. This paper presents an experimental study carried out at the Universidad Polit$\acute{e}$cnica de Valencia with the aim of analysing two different techniques to solve the strengthening close to the joint and the influence on the behaviour of RC columns strengthened steel cages. The ultimate loads obtained in the laboratory tests for these two techniques are compared to that specified by Eurocode 4.