Analytical buckling of slender circular concrete-filled steel tubular columns with compliant interfaces (original) (raw)
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Buckling of Slender Concrete-Filled Steel Tubes with Compliant Interfaces
Latin American Journal of Solids and Structures
This paper presents an exact model for studying the global buckling of concrete-filled steel tubular (CFST) columns with compliant interfaces between the concrete core and steel tube. This model is then used to evaluate exact critical buckling loads and modes of CFST columns. The results prove that interface compliance can considerably reduce the critical buckling loads of CFST columns. A good agreement between analytical and experimental buckling loads is obtained if at least one among longitudinal and radial interfacial stiffnesses is high. The parametric study reveals that buckling loads of CFST columns are very much affected by the interfacial stiffness and boundary conditions.
Analytical Buckling Loads of Concrete-Filled Steel Tubular Columns with Interlayer Slip
2015
This paper presents analytical results for critical buckling loads of circular concrete-filled steel tubular (CFST) columns with interlayer slip between the concrete core and steel tube. The analytical buckling loads of CFST columns are compared to the buckling loads proposed by various design codes and to the experimental results as well. In addition, a parametric study is conducted by which an influence of several geometric and material parameters on buckling loads of CFST columns is investigated.
Investigations on global buckling behaviour of concrete-filled double-skinned steel tubular columns
Proceedings 12th international conference on Advances in Steel-Concrete Composite Structures - ASCCS 2018, 2018
Concrete-Filled Double-skinned Steel Tubular columns (CFDST) are proved to possess exceptional structural resistance in case of fire and multi-hazard situations. This superior quality of CFDST makes it preferable in long column applications. However, studies on the long column behaviour of CFDST is very few, and their results are not in line with the behaviour of CFST long columns. Whereas, several researches on stub column CFDST shows that, the axial compression behaviour of CFDST is similar to CFST. In this paper, selected results (4 numbers of circular CFDST specimens) from a large test data is presented. Axial compression behaviour of long column CFDST specimens is studied, with non-dimensional slenderness λ around 1.0, and hollowness ratio as the governing parameter for study. Test results namely, axial load carrying capacity, axial deformation and lateral deflection are presented in this paper. Numerical models are also developed and validated with the experimental results, to...
Structures, 2020
The behavior of thin-walled round-ended concrete-filled steel tubular (RECFST) short columns loaded axially is characterized by the local-buckling of the flat steel walls and the concrete confinement exerted by the roundended steel walls. A numerical modeling method implementing fiber analysis is presented in this paper for the determination of the behavior of short thin-walled RECFST columns subjected to axial loads. The mathematical simulation method explicitly incorporates the progressive local buckling of the flat steel walls as well as concrete confinement induced by the round-ended tube walls. A new constitutive model is developed by analyzing the available test results for determining the lateral pressures on the concrete confined by the round-ended tube walls. A coefficient of strength degradation is provided to quantify the residual strength of the encased concrete. The independent test results are utilized to assess the accuracy of the computational modeling scheme. Comparative investigations are carried out to evaluate the accuracy of the numerical models of RECFST columns presented by other investigators. The computer modeling program designed is utilized to quantify the structural responses of thin-walled RECFST composite columns subjected to the variations of material and geometric parameters. A design equation is given for designing thin-walled RECFST columns considering local buckling and concrete confinement effects. The applicability of the current design standards for circular and rectangular CFST columns to RECFST columns is assessed by utilizing experimental data. It is found that the current design codes need to be modified to be used to design RECFST thin-walled columns. The proposed computer simulation program and design equation are demonstrated to accurately yield the performance of RECFST columns under axial loading.
Engineering Structures, 2018
Rectangular concrete-filled double steel tubular (CFDST) columns with inner circular steel tube possess higher structural performance than conventional concrete-filled steel tubular (CFST) columns. However, the local buckling of the outer steel tube of thin-walled rectangular CFDST columns has not been accounted for in the existing fiber element models and design codes that may overestimate the column ultimate axial strengths. This paper describes a computationally efficient fiber-based modeling technique developed for determining the behavior of concentrically-loaded rectangular CFDST short columns including the local buckling effects of the external steel tube and the confinement offered by the internal circular steel tube. The effective width concept is used to simulate the post-local buckling of the outer steel tube. Comparative studies are undertaken to verify the fiber-based model with the relevant test results. The computational model is then employed to investigate the axial load-strain responses of rectangular CFDST short columns with various key design variables. A design equation is developed for computing the ultimate axial loads of short rectangular CFDST columns and compared with design methods given in several international design codes. It is shown that the
Local buckling of steel plates in concrete-filled thin-walled steel tubular beam–columns
Journal of Constructional Steel Research, 2007
The availability of high strength steels and concrete leads to the use of thin steel plates in concrete-filled steel tubular beam–columns. However, the use of thin steel plates in composite beam–columns gives a rise to local buckling that would appreciably reduce the strength and ductility performance of the members. This paper studies the critical local and post-local buckling behavior of steel plates in concrete-filled thin-walled steel tubular beam–columns by using the finite element analysis method. Geometric and material nonlinear analyses are performed to investigate the critical local and post-local buckling strengths of steel plates under compression and in-plane bending. Initial geometric imperfections and residual stresses presented in steel plates, material yielding and strain hardening are taken into account in the nonlinear analysis. Based on the results obtained from the nonlinear finite element analyses, a set of design formulas are proposed for determining the critical local buckling and ultimate strengths of steel plates in concrete-filled steel tubular beam–columns. In addition, effective width formulas are developed for the ultimate strength design of clamped steel plates under non-uniform compression. The accuracy of the proposed design formulas is established by comparisons with available solutions. The proposed design formulas can be used directly in the design of composite beam–columns and adopted in the advanced analysis of concrete-filled thin-walled steel tubular beam–columns to account for local buckling effects.
Periodica Polytechnica Civil Engineering, 2020
This paper presents an experimental investigation of the concrete filled thin-walled welded steel tubes. Square and rectangular columns are tested with and without the bond between the steel profile and concrete. In order to remove the bond in the latter columns a polyethylene (PE) film is placed inside of the steel profiles. Experimental results are verified via the finite element analysis and compared to the results obtained using the analytical calculation methods. The significance of the steel-concrete bond is evaluated, referring to the differences of the critical loads, ultimate loads and effective cross-sectional areas of the columns with and without the PE film inside and the differences are found to be considerable. It is found that the columns without the film had an up to 47 % higher effective cross-sectional area to full cross-sectional area ratio. The average reduction of the effective cross-sectional area of the column having a poor bond is found to be 12 %. It is also found that the resistance is often overestimated when using the analytical formulas, especially for the columns with the PE film inside.
A STUDY ON NONLINEAR RESPONSE OF CONCRETE FILLED STEEL TUBULAR COMPOSITE COLUMNS UNDER AXIAL LOADING
IAEME PUBLICATION, 2020
CFST composite columns have been used as bridge piers and columns in multistory buildings etc. It is now widely accepted that concrete filled steel tubular composite columns are well suited as compression members in high-rise buildings, long span, heavy loading and seismic structures. However there are limitations to its applications mainly due to lack of design guidance. This paper deals with the confinement effects of concrete filled steel tubular composite column subjected to different axial loading conditions and the effect of slenderness. The columns were circular in cross-section with constant D/t and slenderness ratio varies from 3 to 12. The experimental study includes for the confinement effect that the axial load applying on the steel only, on the concrete core only and both the concrete and steel. The bond between the steel and internal core concrete was critical in determining the formation of local buckling. In slenderness effect when the slenderness ratio is very low the column fails due to yielding of the steel and crushing. When the slenderness ratio is large, the column fails by elastic buckling.
Seismic Analysis of Partial Concrete-Filled Steel Tubular Columns (CFST)
2016
Steel tubular columns are used in bridge piers in Iraq when necessary and when site conditions limited the work using ordinary R.C. columns. AlTala'a overpass in Baghdad is one of these cases. Since local buckling will occur in the lower part of such columns, it will be necessary to strengthen it through filling by concrete. Thin-walled concrete partially filled steel tubular (CFST) columns may undergo local and global buckling when subjected to seismic loading. The local buckling effects of steel tube walls have not been widely considered in existing numerical models for CFST columns. This work presents a development of a numerical dimensional model for the nonlinear inelastic analysis of thin-walled circular CFST columns under earthquake incorporating the effects of local buckling, and concrete filling level. The numerical model using SAP 2000 V.17 is used to check and calculate the local buckling location and the value of first-buckling load and failure load for five cases of...
Analysis of Concrete-Filled Steel Tubular Beam-Columns
The elastic-plastic behavior of pin-ended, concretefilled steel tubular columns, loaded either symmetrically or unsymmetrically about either of the two axes is studied using the Column Curvature Curve method. Two types of cross section are considered: circular shapes and square shapes. Three types of stress-strain relationship for concrete are studied: