Concrete-filled thin-walled steel SHS and RHS beam-columns subjected to cyclic loading (original) (raw)
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Finite Element Analysis of Ultimate Load Capacity of Slender Concrete-Filled Steel Composite Columns
International Journal on Advanced Science, Engineering and Information Technology, 2011
Ultimate load capacity of slender concrete-filled steel composite columns is investigated in this paper. Nonlinear analyses are done by the use of finite element software, LUSAS, to study the ultimate axial load behaviour of the columns. Verification of the finite element modelling is done by comparing the result with the corresponding experimental result reported by other researchers. Analyses are carried out to assess different shapes and number of cold-formed steel sheeting stiffeners with various thicknesses of cold-formed steel sheets and their effects on the behaviour and ultimate axial load capacity of the columns. The results are presented in the form of axial load-normalized axial shortening plots. It is demonstrated that the ultimate axial load capacity of the slender concrete-filled steel composite columns can be accurately predicted by proposed finite element modelling. Obtained results from the study show that various thicknesses of cold-formed steel sheets, and different shapes and number of stiffeners influence the ultimate axial load capacity and behaviour of the columns. Also, the ultimate axial load capacity of the columns is improved by increase of number of stiffeners. Moreover, increase of thickness of cold-formed steel sheet enhances the ultimate axial load capacity.
IAEME Publication, 2018
The current paper is a report on the preparation and testing of 10 reinforced concrete column specimens of (120x120) mm2 cross section and 1000 mm height, for the experimental clarification of the behavior of columns under the influence of pure axial loads. The research addresses the influences of some parameters and conditions on the mentioned behavior, including concrete type (normal strength, high strength or modified reactive powder concrete), the amount of reinforcement and the percentage of steel fibers. The effects of the above variables on the ultimate capacity, failure mode, stiffness, ductility and axial load-lateral displacement behavior were studied. It has been found that increasing the compressive strength and steel reinforcement ratio lead to increasing the ultimate capacity and stiffness of the tested columns. The effectiveness of increasing the steel fibers ratio is manifest in increasing the ultimate strength, ductility, and decreasing the stiffness and the ductility of the tested columns.
Behaviour of reinforced and concrete-encased composite columns
2014
An experimental investigation of the behaviour of reinforced concrete columns and a theoretical procedure for analysis of both short and slender reinforced and composite columns of arbitrarily shaped cross section subjected to biaxial bending and axial load are presented. In the proposed procedure, nonlinear stress-strain relations are assumed for concrete, reinforcing steel and structural steel materials. The compression zone of the concrete section and the entire section of the structural steel are divided into adequate number of segments in order to use various stress-strain models for the analysis. The slenderness effect of the member is taken into account by using the Moment Magnification Method. The proposed procedure was compared with test results of 12 square and three L-shaped reinforced concrete columns subjected to short-term axial load and biaxial bending, and also some experimental results available in the literature for composite columns compared with the theoretical results obtained by the proposed procedure and a good degree of accuracy was obtained. r
International Journal of Advanced Structural Engineering, 2014
The need of strengthening reinforced concrete columns, due to loss of strength and/or stiffness, is an essential requirement due to variation of the loads and environmental conditions applied on these columns. Steel jackets around the reinforced concrete (RC) columns are usually made by means of steel plates covering all over the column surface area. For the value of engineering purposes, another technique was developed using steel angles at the corners of the RC columns connected with discrete steel strips. In this paper, an experimental program is designed to evaluate the improvement in loadcarrying capacity, stiffness and ductility of strengthened RC columns, concomitant with steel angles and strips. Despite of prevailing a substantially increased loading capacity and strength a pronounced enhancement in ductility and stiffness has been reported. A need for experimental test results with low value of concrete strength to mimic the local old-age structures condition that required strengthening in local countries. Seven columns specimens are tested to evaluate the strength improvement provided by steel strengthening of columns. The method of strengthened steel angles with strips is compared with another strengthening technique. This technique includes connected and unconnected steel-casing specimens. The observed experimental results describe load-shortening curves, horizontal strains in stirrups and steel strips, as well as description of failure mode. The extra-confinement pressure, due to existence of steel cage, of the strengthened RC column can be also observed from experimental results. The code provisions that predict the load-carrying capacity of the strengthened RC composite column has a discrepancy in the results. For this reason, an analytical model is developed in this paper to compare the code limit with experimental observed results. The proposed model accounts for the composite action for concrete confinement and enhancement of the local buckling of steel elements. This adopted model is simplified and applicable to practical design field. In this respect, the experimental results and those of the analytical model showed a good agreement.
Steel-reinforced concrete-filled steel tubular columns under axial and lateral cyclic loading
International Journal of Advanced Structural Engineering
SRCFT columns are formed by inserting a steel section into a concrete-filled steel tube. These types of columns are named steel-reinforced concrete-filled steel tubular (SRCFT) columns. The current study aims at investigating the various types of reinforcing steel section to improve the strength and hysteresis behavior of SRCFT columns under axial and lateral cyclic loading. To attain this objective, a numerical study has been conducted on a series of composite columns. First, FEM procedure has been verified by the use of available experimental studies. Next, eight composite columns having different types of cross sections were analyzed. For comparison purpose, the base model was a CFT column used as a benchmark specimen. Nevertheless, the other specimens were SRCFT types. The results indicate that reinforcement of a CFT column through this method leads to enhancement in load-carrying capacity, enhancement in lateral drift ratio, ductility, preventing of local buckling in steel shell, and enhancement in energy absorption capacity. Under cyclic displacement history, it was observed that the use of cross-shaped reinforcing steel section causes a higher level of energy dissipation and the moment of inertia of the reinforcing steel sections was found to be the most significant parameter affecting the hysteresis behavior of SRCFT columns.
Behavior of Slender Reinforced High Performance Concrete Columns under Biaxial Loading
Columns are structural elements used primarily to support compressive loads. The short column is one in which the ultimate load at a given eccentricity is governed only by the strength of the materials and the dimensions of cross section. Slender concrete columns are economically appealing in tall buildings design; the rentable space over the many floors can be increased by a substantial margin through reduction of the column sections. The slenderness of a column may result in the ultimate load being reduced by lateral deflections of the column caused by bending. Reinforced concrete columns are generally subjected to eccentric compression as a result of their location in the structure, their cross section or the type of forces they bear. Many columns are subjected to this kind of loads, for example the corner columns of a building. The analysis of slender reinforced concrete columns is complicated because the buckling analysis must take account of the non-linear properties of the materials and also construction imperfections. Exact analysis methods are generally complicated and unsuitable for everyday design. Over the last few decades, the development in material technology, especially with the availability of super plasticizers, led to the production of High Performance Concrete. With the robust growth of construction with HPC, the design of slender concrete columns is now a subject of considerable relevance. One application of HPC has been in the columns of high-rise buildings. Buckling has become more of a problem in recent years since the use of high-strength materials requires less material for load support-structures and components have become generally more slender and buckle-prone. Key words Reinforced concrete column, slenderness ratio, high performance concrete column, bi-axial loading and P-M Interaction diagram. Introduction Columns are structural elements used primarily to support compressive loads. The short column is one in which the ultimate load at a given eccentricity is governed only by the strength of the materials and the dimensions of cross section. A slender column is one in which the ultimate load is governed not only by the strength of the materials and the dimensions of the cross section but also by the slenderness, which produces additional bending moment due to lateral deformations. For eccentrically loaded short columns, the column behavior will follow the linear path until intersect the interaction diagram. For eccentrically loaded slender columns, the column will follow a non-linear path until intersects the interaction diagram. This means that, due to non-linear effects the actual moment on the column is greater than the linear moment. [1] Slender concrete columns are economically appealing in tall buildings design; the rentable space over the many floors can be increased by a substantial margin through reduction of the column sections. The slenderness of a column may result in the ultimate load being reduced by lateral deflections of the column caused by bending. Reinforced concrete columns are generally subjected to eccentric compression as a result of their location in the structure, their cross section or the type of forces they bear. Many columns are subjected to this kind of loads, for example the corner columns of a building. The analysis of slender reinforced concrete columns is complicated because the buckling analysis must take account of the non-linear properties of the materials and also construction imperfections. Exact analysis methods are generally complicated and unsuitable for everyday design. [2] Over the last few decades, the development in material technology, especially with the availability of super plasticizers, led to the production of High Performance Concrete [3]. With the robust growth of construction with HPC, the design of slender concrete columns is now a subject of considerable relevance. One application of HPC has been in the columns of high-rise buildings. Buckling has become more of a problem in recent years since the use of high-strength materials requires less material for load support-structures and components have become generally more slender and buckle-prone. As a result, the slenderness limits based on normal strength concrete (NSC) have to be reassessed to make use of the merits of HPC. Attempts have been made to modify the theory of analysis of slender columns by introducing effects of inelastic behavior and large deformations. There are two important limits for the slenderness ratio, which are the upper limit for the short column and maximum slenderness limit. The upper slenderness limit is the limit that when the column exceeded is considered a long column. On the other hand, the maximum slenderness limit is stipulated to avoid carrying out second order analysis of the column, which is burdensome and more complicated [1].
Journal of Constructional Steel Research, 2014
The effects of cyclic local buckling on the behavior of concrete-filled steel tubular (CFST) slender beam-columns under cyclic loading were approximately considered in existing analytical methods by modifying the stressstrain curve for the steel tube in compression. These methods, however, cannot simulate the progressive cyclic local buckling of the steel tubes. This paper presents a new efficient numerical model for predicting the cyclic performance of high strength rectangular CFST slender beam-columns accounting for the effects of progressive cyclic local buckling of steel tube walls under stress gradients. Uniaxial cyclic constitutive laws for the concrete core and steel tubes are incorporated in the fiber element formulation. The effects of initial geometric imperfections, high strength materials and second order are also included in the nonlinear analysis of CFST slender beam-columns under constant axial load and cyclically varying lateral loading. The Müller's method is adopted to solve nonlinear equilibrium equations. The accuracy of the numerical model is examined by comparisons of computer solutions with experimental results available in the published literature. A parametric study is conducted to investigate the effects of cyclic local buckling, column slenderness ratio, depth-to-thickness ratio, concrete compressive strength and steel yield strength on the cyclic responses of CFST slender beamcolumns. It is shown that the numerical model developed predicts well the experimentally observed cyclic lateral load-deflection characteristics of CFST slender beam-columns. The numerical results presented reflect the cyclic local and global buckling behavior of thin-walled high strength rectangular CFST slender beam-columns, which have not been reported in the literature.
Building and Environment, 2008
An experimental investigation of the behaviour of reinforced concrete columns and a theoretical procedure for analysis of both short and slender reinforced and composite columns of arbitrarily shaped cross section subjected to biaxial bending and axial load are presented. In the proposed procedure, nonlinear stress-strain relations are assumed for concrete, reinforcing steel and structural steel materials. The compression zone of the concrete section and the entire section of the structural steel are divided into adequate number of segments in order to use various stress-strain models for the analysis. The slenderness effect of the member is taken into account by using the Moment Magnification Method. The proposed procedure was compared with test results of 12 square and three L-shaped reinforced concrete columns subjected to short-term axial load and biaxial bending, and also some experimental results available in the literature for composite columns compared with the theoretical results obtained by the proposed procedure and a good degree of accuracy was obtained. r
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.
Behavior of fully encased steel-concrete composite columns subjected to monotonic and cyclic loading
Istrazivanja i projektovanja za privredu, 2014
The paper presents a numerical model developed for fully encased steel-concrete composite columns under monotonic and cyclic loading. The numerical model was realized with the FineLg program, developed at ArGenCo department, University of Liège. The numerical model was validated using five experimental tests taken from the international literature: two realised at Technical University of Cluj-Napoca and the others in Taiwan, USA and China. The experimental tests used for validation of the numerical model dealt with both normal and high strength concrete. Different parameters were compared in the paper: partial and full ductility, energy dissipation, resistance and rigidity ratio.