• Steel and Composite Structures
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• 제22권2호
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• pp.217-234
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• 2016

In order to investigate mechanical properties and load-bearing capacity of T-shaped Concrete-Filled Square Steel Tubular (TCFST) composite columns under eccentric axial load, three T-shaped composite columns were tested under eccentric compression. Experimental results show that failure mode of the columns under eccentric compression was bending buckling of the whole specimen, and mono column performs flexural buckling. Specimens behaved good ductility and load-bearing capacity. Nonlinear finite element analysis was also employed in this investigation. The failure mode, the load-displacement curve and the ultimate bearing capacity of the finite element analysis are in good agreement with the experimental ones. Based on eccentric compression test and parametric finite element analysis, the calculation formula for the equivalent slenderness ratio was proposed and the bearing capacity of TCFST composite columns under eccentric compression was calculated. Results of theoretical calculation, parametric finite element analysis and eccentric compression experiment accord well with each other, which indicates that the theoretical calculation method of the bearing capacity is advisable.

• Steel and Composite Structures
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• 제23권1호
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• pp.87-94
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• 2017

Steel structures often require strengthening due to the increasing life loads, or repair caused by corrosion or fatigue cracking. Carbon Fiber Reinforced Polymers (CFRP) is one of the materials used to strengthen steel structures. Most studies on strengthening steel structures have been carried out on steel beams and steel columns under centric compression load. No independent article, to the author's knowledge, has studied the effect of CFRP strengthening on steel columns under eccentric compression load, and it seems that there is a lack of understanding on behavior of CFRP strengthening on steel columns under eccentric compression load. However, this study explored the use of adhesively bonded CFRP flexible sheets on retrofitting square hollow section (SHS) steel columns under the eccentric compression load, using numerical investigations. Finite Element Method (FEM) was employed for modeling. To determine ultimate load of SHS steel columns, eight specimens with two types of section (Type A and B), strengthened using CFRP sheets, were analyzed under different coverage lengths, the number of layers, and the location of CFRP composites. Two specimens were analyzed without strengthening (control) to determine the increasing rate of the ultimate load in strengthened steel columns. ANSYS was used to analyze the SHS steel columns. The results showed that the CFRP composite had no similar effect on the slender and stocky SHS steel 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 columns.

• Steel and Composite Structures
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• 제38권1호
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• pp.103-120
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• 2021

This research examines the eccentric compression performance of composite columns composed of recycled aggregate concrete (RAC)-filled square steel tube and profile steel. A total of 17 specimens on the composite columns with different recycled coarse aggregate (RCA) replacement percentage, RAC strength, width to thickness ratio of square steel tube, profile steel ratio, eccentricity and slenderness ratio were subjected to eccentric compression tests. The failure process and characteristic of specimens under eccentric compression loading were observed in detail. The load-lateral deflection curves, load-train curves and strain distribution on the cross section of the composite columns were also obtained and described on the basis of test data. Results corroborate that the failure characteristics and modes of the specimens with different design parameters were basically similar under eccentric compression loads. The compression side of square steel tube yields first, followed by the compression side of profile steel. Finally, the RAC in the columns was crushed and the apparent local bulging of square steel tube was also observed, which meant that the composite column was damaged and failed. The composite columns under eccentric compression loading suffered from typical bending failure. Moreover, the eccentric bearing capacity and deformation of the specimens decreased as the RCA replacement percentage and width to thickness ratio of square steel tube increased, respectively. Slenderness ratio and eccentricity had a significantly adverse effect on the eccentric compression performance of composite columns. But overall, the composite columns generally had high-bearing capacity and good deformation. Meanwhile, the mechanism of the composite columns under eccentric compression loads was also analysed in detail, and the calculation formulas on the eccentric compression capacity of composite columns were proposed via the limit equilibrium analysis method. The calculation results of the eccentric compression capacity of columns are consistent with the test results, which verify the validity of the formulas, and the conclusions can serve as references for the engineering application of this kind of composite columns.

• Steel and Composite Structures
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• 제42권5호
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• pp.617-631
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• 2022

To study the eccentric compressive performance of the basalt-fiber reinforced recycled aggregate concrete (BFRRAC)-filled circular steel tubular stub column, 8 specimens with different replacement ratios of recycled coarse aggregate (RCA), basalt fiber (BF) dosage, strength grade of recycled aggregate concrete (RAC) and eccentricity were tested under eccentric static loading. The failure mode of the specimens was observed, and the relationship curves during the entire loading process were obtained. Further, the load-lateral displacement curve was simulated and verified. The influence of the different parameters on the peak bearing capacity of the specimens was analyzed, and the finite element analysis model was established under eccentric compression. Further, the design-calculation method of the eccentric bearing capacity for the specimens was suggested. It was observed that the strength failure is the ultimate point during the eccentric compression of the BFRRAC-filled circular steel tubular stub column. The shape of the load-lateral deflection curves of all specimens was similar. After the peak load was reached, the lateral deflection in the column was rapidly increased. The peak bearing capacity decreased on enhancing the replacement ratio or eccentric distance, while the core RAC strength exhibited the opposite behavior. The ultimate bearing capacity of the BFRRAC-filled circular steel tubular stub column under eccentric compression calculated based on the limit analysis theory was in good agreement with the experimental values. Further, the finite element model of the eccentric compression of the BFRRAC-filled circular steel tubular stub column could effectively analyze the eccentric mechanical properties.

• Structural Engineering and Mechanics
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• 제71권3호
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• pp.211-221
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• 2019

To study the eccentric compression behavior of ultra-high performance fiber reinforced concrete (UHPFRC) columns, six UHPFRC columns and one high-strength concrete (HSC) column were tested. Variation parameters include load eccentricity, volume of steel fibers and stirrup ratio. The crack pattern, failure mode, bearing capacity, and deformation of the specimens were studied. The results showed that the UHPFRC columns had different failure modes. The large eccentric compression failure mode was the longitudinal tensile reinforcements yielded and many horizontal cracks appeared in the tension zone. The small eccentric compression failure mode was the longitudinal compressive reinforcements yielded and vertical cracks appeared in the compressive zone. Because of the bridging effect of steel fibers, the number of cracks significantly increased, and the width of cracks decreased. The load-deflection curves of the UHPFRC columns showed gradually descending without sudden dropping, indicating that the specimens had better deformation. The finite element (FE) analysis was performed to stimulate the damage process of the specimens with monotonic loading. The concrete damaged plasticity (CDP) model was adopted to characterize the behaviour of UHPFRC. The contribution of the UHPFRC tensile strength was considered in the bearing capacity, and the theoretical calculation formulas were derived. The theoretical calculation results were consistent with the test results. This research can provide the experimental and theoretical basis for UHPFRC columns in engineering applications.

• Advances in concrete construction
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• 제10권2호
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• pp.151-159
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• 2020

An experimental study on the stress-strain relation of PVC-CFRP confined reinforced concrete columns subjected to eccentric compression was carried out. Two parameters, such as the CFRP strips spacing and eccentricity of axial load, were considered. The experimental results showed that all specimens failed by compressive yield of longitudinal steel bar and rupture of CFRP strips. The bearing capacity of specimen decreases as the eccentricity or the CFRP strips spacing increases. The stress-strain relation of specimens undergoes two stages: parabolic and linear stages. In the parabolic stage, the slope of stress-strain curve decreases gradually as the eccentricity of axial loading increases while the CFRP strips spacing has little effect on the slope of stress-strain curve. For the linear stage, the slope of stress-strain curve decreases as the eccentricity of axial load or the CFRP strips spacing increases. A model for predicting the stress-strain relation of columns under eccentric compression is proposed and it agrees well with various test data.

• Advances in concrete construction
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• 제13권 2호
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• pp.163-181
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• 2022

To study the mechanical properties of steel reinforced recycled concrete (SRRC) filled circular steel tube columns under eccentric compression loads, this study presents a finite element model which can simulate the eccentrically compressed columns using ABAQUS software. The analytical model was established by selecting the reasonable nonlinear analysis theory and the constitutive relationship of materials in the columns. The influences of design parameters on the eccentric compressive performance of columns were also considered in detail, such as the diameter-thickness ratio of circular steel tube, replacement percentage of recycled coarse aggregate (RCA), slenderness ratio, eccentricity, recycled aggregate concrete (RAC) strength and steel strength and so on. The deformation diagram, stress nephogram and load-displacement curves of the eccentrically compressed columns were obtained and compared with the test results of specimens. The results show that although there is a certain error between the calculation results and the test results, the error is small, which shows the rationality on the numerical model of eccentrically compressed columns. The failure of the columns is mainly due to the symmetrical bending of the columns towards the middle compression zone, which is a typical compression bending failure. The eccentric bearing capacity and deformation capacity of columns increase with the increase of the strength of steel tube and profile steel respectively. Compared with profile steel, the strength of steel tube has a greater influence on the eccentric compressive performance of columns. Improving the strength of RAC is beneficial to the eccentric bearing capacity of columns. In addition, the eccentric bearing capacity and deformation capacity of columns decrease with the increase of replacement percentage of RCA. The section form of profile steel has little influence on the eccentric compression performance of columns. On this basis, the calculation formulas on the nominal eccentric bearing capacity of columns were also put forward and the results calculated by the proposed formulas are in good agreement with the test values.

• 대한안전경영과학회지
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• 제26권1호
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• pp.9-14
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• 2024

Restraints of Branch Lines are used as earthquake-resistant support devices for fire-fighting pipes along with sway brace devices. The central types are aligned and fixed in a straight line with center of the pipe, but the eccentric types are fixed to on side of the pipe, so a bending moment occurs. In this study, three specimens each of central type and eccentric type were installed at an angle of 45° from the vertical and a monotonic compression load of 1340N was applied. All central type samples satisfied 17.8mm of the allowable displacement, but all eccentric type samples failed to meet the target load and buckled. Therefore, when considering the performance of eccentric type restraints, both compressive load and bending moment must be considered. Even through material mechanics calculations, the yield stress of eccentric type - 3/8 inch all threaded steel bolt - exceeds 320Mpa of the allowable stress. A experiment standards need to be established for eccentric type restraints.

• Structural Engineering and Mechanics
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• 제50권3호
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• pp.287-304
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• 2014

A computer based iterative numerical procedure has been developed to analyse reinforced high strength concrete columns subjected to horizontal wave loads and eccentric vertical load by taking the material, geometrical and wave load non-linearity into account. The behaviour of the column has been assumed, to be represented by Moment-Thrust-Curvature relationship of the column cross-section. The formulated computer program predicts horizontal load versus deflection behaviour of a column up to failure. The developed numerical model has been applied to analyse several column specimens of various slenderness, structural properties and axial load ratios, tested by other researchers. The predicted values are having a better agreement with experimental results. A simplified user friendly hydrodynamic load model has been developed based on Morison equation supplemented with a wave slap term to predict the high frequency non-linear impulsive hydrodynamic loads arising from steep waves, known as ringing loads. A computer program has been formulated based on the model to obtain the wave loads and non-dimensional wave load coefficients for all discretised nodes, along the length of column from instantaneous free water surface to bottom of the column at mud level. The columns of same size and material properties but having different slenderness ratio are analysed by the developed numerical procedure for the simulated wave loads under various vertical thrust. This paper discusses the results obtained in detail and effect of slenderness in resisting wave loads under various vertical thrust.

• Steel and Composite Structures
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• 제22권3호
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• pp.663-675
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• 2016

The effects of slenderness ratio, eccentricity and column slope on the load-carrying capacities and failure modes of variable and uniform concrete filled steel tubular (CFST) latticed columns under axial and eccentric compression were investigated and compared in this study. The results clearly show that all the CFST latticed columns with variable cross section exhibit an overall failure, which is similar to that of CFST latticed columns with a uniform cross section. The load-carrying capacity decreases with the increase of the slenderness ratio or the eccentricity. For 2-m specimens with a slenderness ratio of 9, the ultimate load-carrying capacity is increased by 3% and 5% for variable CFST latticed columns with a slope of 1:40 and 1:20 as compared with that of uniform CFST latticed columns, respectively. For the eccentrically compressed variable CFST latticed columns, the strain of the columns at the loading side, as well as the difference in the strain, increases from the bottom to the cap, and a more significant increase in strain is observed in the cross section closer to the column cap.