Behaviour of eccentrically loaded high-strength rectangular concrete-filled steel tubular columns (original) (raw)
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Experimental study of high strength concrete-filled circular tubular columns under eccentric loading
Journal of Constructional Steel Research, 2011
The paper describes 37 tests conducted on slender circular tubular columns filled with normal and high strength concrete subjected to eccentric axial load. The test parameters were the nominal strength of concrete (30, 70 and 90 MPa), the diameter to thickness ratio D/t, the eccentricity ratio e/D and the column slenderness (L/D). The experimental ultimate load of each test was compared with the design loads from Eurocode 4, which limits the strength of concrete up to 50 MPa. The aim of the paper is to establish the advisability of the use of high strength concretes as opposed to that of normal strength concretes by comparing three performance indices: concrete contribution ratio, strength index and ductility index. The results show for the limited cases analyzed that the use of high strength concrete for slender composite columns is interesting since this achieves ductile behavior despite the increase in load-carrying capacity is not greatly enhanced.
Journal of Constructional Steel Research, 2012
The paper describes 36 experimental tests conducted on rectangular and square tubular columns filled with normal and high strength concrete and subjected to a non-constant bending moment distribution with respect to the weak axis. The test parameters were the nominal strength of concrete (30 and 90 MPa), the cross-section aspect ratio (square or rectangular), the thickness (4 or 5 mm) and the ratio of the top and bottom first order eccentricities e top /e bottom (1, 0.5, 0 and-0.5). The ultimate load of each test was compared with the design loads from Eurocode 4, presenting unsafe results inside a 10% safety margin. The tests show that the use of high strength concrete is more useful for the cases of non-constant bending moment, whereas if the aim is to obtain a more ductile behavior the use of concrete-filled columns is more appealing in the cases of normal strength concrete with non-constant bending moments because, although they resist less axial force than the members with HSC, they obtain a softened post-peak behavior.
Engineering Structures, 2019
Square concrete-filled double steel tubular (CFDST) beam-columns consisting of an internal circular steel tube have increasingly been utilized in composite building structures because of their high structural performance. This paper describes experimental and numerical studies on the structural responses of square thin-walled CFDST columns loaded eccentrically. Tests on twenty short square CFDST columns were undertaken that included sixteen columns under eccentric loading and four columns under concentric loading. The parameters examined in the experiments included the cross-sectional dimensions, the width-to-thickness ratios of outer and internal tubes and loading eccentricity. The measured ultimate strengths, load-shortening responses, load-lateral displacement curves, stress-strain curves and observed failure modes are presented. A numerical model incorporating the fiber analysis is developed that predicts the moment-curvature responses and axial load-moment strength envelopes of CFDST columns.
Thin-Walled Structures, 2018
Using high strength materials in concrete filled steel tube (CFST) columns is expected to achieve better structural performance and fulfil the requirements of sustainable construction. To study the mechanical behaviour of eccentrically loaded high strength concrete filled high strength square steel tube (HCFHSST) stub columns, this paper describes 12 tests with different eccentricity ratios and steel ratios. The cubic strength of high strength concrete under investigation was 110.5 MPa, and the yield strength of the high strength steel was about 434 MPa. Curves of load-lateral deformation were presented, along with values of ductility index, and the minimum ductility index based on the steel ratio of columns was suggested. Finite element analysis (FEA) software ABAQUS was applied to simulate HCFHSSTs. The analytical results were in good agreement with the experimental ones. The load-lateral deformation curve was divided into four stages: elastic, elastic-plastic, plastic hardening and descending. The confinement effect of steel tube at various stages was analysed. The parametric studies were carried out to evaluate the influences of the eccentricity ratio, concrete compressive strength, steel yield strength and steel ratio on the strength reduction factor (SRF), concrete contribution ratio (CCR), P-M and P/P u-M/M u interaction curves of the HCFHSST members. The bending moments at balanced points of P/P u-M/M u curves calculated by the plastic stress distribution models (PSDM) and FEA models were compared. The ultimate bearing capacities obtained from the tests and the values calculated from the AISC 360, GB 50936 and CECS 28: 90 design codes were compared. Finally, the formulas were proposed to predict the P/ P u-M/M u curves for the HCFHSST stub columns subjected to eccentric load. The proposed formulas' predictions agreed well with the test results.
An experimental behaviour of concrete-filled steel tubular columns
Journal of Constructional Steel Research, 2005
In this paper results of tests conducted on 27 concrete-filled steel tubular columns are reported. The test parameters were the column slenderness, the load eccentricity covering axially and eccentrically loaded columns with single or double curvature bending and the compressive strength of the concrete core. The test results demonstrate the influence of these parameters on the strength and behaviour of concrete-filled steel tubular columns. A comparison of experimental failure loads with the predicted failure loads in accordance with the method described in Eurocode 4 Part 1.1 showed good agreement for axially and eccentrically loaded columns with single curvature bending whereas for columns with double curvature bending the Eurocode loads were higher and on the unsafe side. More tests are needed for the case of double curvature bending.
Proceedings of the 7th International Conference on Civil, Structural and Transportation Engineering (ICCSTE'22)
This paper presents an experimental investigation on circular concrete-filled double steel tubular (CFDST) slender columns under axial loading. The test parameters include the column slenderness ratio and the thickness of the inner steel tube. Test results show that the common failure mode of CFDST slender columns is the global failure of the columns. It is found that increasing the column slenderness decreases the ultimate strengths of the columns and the thickness of the inner steel has an insignificant influence on the ultimate strength of the columns. The design model specified by Eurocode 4 for conventional CFST slender columns is shown to overestimate the ultimate strength of CFDST slender columns under axial loading.
Experimental and computational study of concrete filled steel tubular columns under axial loads
Journal of Constructional Steel Research, 2007
The paper presents an experimental and computational study on the behaviour of circular concentrically loaded concrete filled steel tube columns till failure. Eighty-one specimens were tested to investigate the effect of diameter and D/t ratio of a steel tube on the load carrying capacity of the concrete filled tubular columns. The effect of the grade of concrete and volume of flyash in concrete was also investigated. The effect of these parameters on the confinement of the concrete core was also studied. Diameter to wall thickness ratio between 25 < D/t < 39, and the length to tube diameter ratio of 3 < L/D < 8 was investigated. Strength results of Concrete Filled Tubular columns were compared with the corresponding findings of the available literature. Also a nonlinear finite element model was developed to study the load carrying mechanism of CFTs using the Finite Element code ANSYS. This model was validated by comparison of the experimental and computational results of load-deformation curves and their corresponding modes of collapse. From the experimental and computational study it was found that for both modes of collapse of concrete filled tubular columns at a given deflection the load carrying capacity decreases with the increase in % volume of flyash up to 20% but it again increases at 25% flyash volume in concrete.
MATEC Web of Conferences, 2020
The article deals with the integrated approach to the study of the behaviour of rectangular CFST columns under eccentric compression. Such an approach includes the development of methods for assessing the magnitude of the carrying capacity, assessing the degree of reliability and credibility of the obtained results, as well as studying the nature of the development of columns deformations at various stages of loading. The authors developed a mathematical model for calculation of columns carrying capacity under eccentric compression based on statistical methods. Substantial amount of experimental data collected by the world leading laboratories enabled obtaining a regression dependence of the columns carrying capacity that takes into account the impact of the physical and geometric characteristics of such structures. High degree of model confidence is confirmed by a comparative analysis with experimental results that are not involved in the development of the model, as well as with c...
Behavior of eccentrically loaded double circular steel tubular short columns filled with concrete
Engineering Structures, 2019
Circular concrete-filled double steel tubular (CFDST) columns in high-rise building structures possess high ductility and strength performance owing to the concrete confinement exerted by the external and internal circular steel tubes. However, the behavior of circular CFDST short columns that are loaded eccentrically has not been investigated either experimentally or numerically. Particularly, numerical studies on the moment-curvature responses, strength envelopes, confinement effects and moment distributions in circular CFDST beam-columns have not been reported. In this paper, experimental and computational investigations into the structural responses of circular CFDST short columns loaded eccentrically are presented. Nineteen short circular CFDST columns with various parameters under axial and eccentric loads were tested to failure to measure their structural responses. Test results are presented and discussed. A mathematical simulation model underlying the method of fiber analysis is proposed that simulates the axial load-moment-curvature relationships as well as the strength interaction curves of CFDST beam-columns composed of circular sections. The mathematical modeling technique explicitly takes into account the confinement of concrete on the responses
Performance of Concrete Filled Steel Tubular Columns
Recent advancements in the availability of higher strength steels, better coating materials for protection and high strengths/performance concretes have expanded the scope of concrete filled steel composite columns with wide ranging applications in various structural systems with ease of construction, highly increased strengths and better performance. This experimental study is carried out on the behavior of short, concrete filled steel tubular columns axially loaded in compression to failure. Three dimensional confinement effect of concrete along with support provided by concrete to the thin walls of steel tube to prevent local buckling had a composite effect on the strength of the composite column increasing the compressive strengths by almost 300 to 400%. In addition to the concrete core, the parameters for the testing were shape of the steel tube and its diameter-to-thickness ratio. It has been observed that ultimate strength of concrete filled steel tubes under concentric compression behavior is considerably affected by the thickness of the steel tube, as well as by the shape of its cross section. Confining effect in circular CFST columns improves their strength, appreciably. The axial load-deformation behavior of columns is remarkably affected by the cross-sectional shape, diameter/width-to-thickness ratio of the steel tube, and the strength of the filled concrete. The load deformation relationship for circular columns showed strain-hardening or elastic perfectly plastic behavior after yielding.