Steel Tube Short Columns Research Articles

Finite Element Analysis on Concrete-Filled Square Steel Tube Short Columns with Inner CFRP Profiles under Axial Compression

The new composite structure concrete-filled square steel tube (CFST) column with inner CFRP profiles is proposed. A finite element model is presented to investigate the mechanical behavior of CFST short columns with internal CFRP profiles subjected to axial compression using ABAQUS based on reasonable constitutive models of materials. In a addition, the content of CFRP profiles and width thickness ratio of steel tube’ effect are considered on mechanical properties of the column. Based on the model, the whole stage of axial compression of the short columns, failure mode and the stress mechanism of the ultimate bearing capacity state are calculated and analyzed.

コンクリート充填角形鋼管短柱の軸圧縮性状に及ぼす断面寸法・形状の影響に関する実験的研究

The purpose of this research is to clarify the effect of cross sectional size and shape on the uni-axial compressive behavior of concrete filled square steel tube (CFT) short columns. Compression tests of square CFT short columns with cross sectional size 400mm have been conducted. This paper first presents the test results concerning compressive strength, and discusses the evaluation of the strength of square CFT short columns considering the effects of cross sectional size and shape. As a result, following have been found. i) effects of cross sectional size and shape on the square CFT short columns were clearly observed, ii) the compressive strength of various size square CFT short columns can be predicted by proposed numerical formula.

EXPERIMENTAL STUDY AND THEORETICAL ANALYSIS ON AXIAL COMPRESS CAPACITY OF ERCYCLED AGGREGATE CONCRETE-FILLED CIRCLE STEEL TUBE SHORT COLUMN

In order to study the axial compress capacity of recycled aggregate concrete-filled steel tube short-columns, 22 specimens were designed to test, and the recycled coarse aggregate replacement percentage and confinement index were regarded as major variable parameters. By the experiment, the whole mechanical process and failure mode of all specimens were observed, and stress-strain curves of the specimens were obtained. The influence of the aggregate replacement rate and confinement index on the bearing behaviour of the specimens was analyzed. The test results indicate that the failure mode of the columns is similar to that of an ordinary concrete-filled steel tube, and recycled coarse aggregate replacement rate has little effect on a recycled aggregate concrete-filled steel tube, but confinement index has a significant effect on the bearing behaviour and deformation performance. The bearing capacity of the specimens was calculated and analyzed according to the theories of Unified Strengthen, Confinement and Superposition Calculation. Compared with the experimental values, the results show that calculated values are low on the basis of the first and the third calculation theories, but the calculated values are slightly high based on the second calculation theory. Finally, stress-strain curves were fitted and analyzed according to experimental data. Stress-strain whole curve equations of specimens were put forward. The research conclusions could be a reference for the scientific study and engineering application of recycled aggregate concrete-filled steel tubes.

Optimal Calculation Method of Eccentric Bearing Capacity of Concrete-Filled Steel Tube Short Columns

The currently formulae with many coefficients are too complicated to calculate the bearing capacity of concrete-filled steel tube (CFST) short columns. In this paper, an optimal calculation method was proposed for calculating the eccentric bearing capacity of CFST short columns by means of mechanical derivation. Additionally, the calculating results are compared with experimental data. It is shown that the optimal calculating formulae are highly accurate and easily applicable in engineering design.

Nonlinear Finite Element Analysis of Stiffened T-Shaped Thin-Walled Concrete-Filled Steel Tube Composite Columns

Based on the characteristics of the special-shaped concrete-filled steel tubes and consideration of material nonlinearity of constitutive relation, stimulation of 6 T-shaped thin-walled ribbed and un-ribbed concrete-filled steel tube short columns is implemented, as well as comparable analysis of stress, strain, displacement and bearing capacity, through the finite element analysis software ANSYS. The result indicates that the rib can effectively improve the ductility, delaying the buckling occurs, which enhances the core concrete confinement effect, so as the stimulated ultimate bearing capacity which is greater than nominal ultimate bearing capacity.

Confined Expansion and Bond Property of Micro-Expansive Concrete- Filled Steel Tube Columns

The shrinkage/expansion behavior and bond carrying capacities were investigated through 4 micro-expensive concrete-filled steel tube(MCFST) and 3 conventional concrete-filled steel tube(CFST) short columns. The results show that the temperature field in MCFST is similar to that of ordinary concrete members. Concrete core has obvious effect on shrinkage-compensating with the addition of swelling agent. Pre-stress is produced in the core concrete when it is confined by the steel tube. Both water cement ratio and expansive agent have obvious influence on expansive behaviors of MCFST. The tests also indicate that the pre-stress in core concrete can improve bond strength of core concrete and steel tube of MCFST columns and proposed a new method to improve the interface bond strength of composite structures.

The Experimental Study on Concrete-Filled Thin-Walled Square Steel Tube Short Columns Fixed U-Shaped Steel Bars

Based on the compression characteristics of the concrete-filled thin-walled square steel tube short columns, the U-shaped tie bars are designed in this paper. The U-shaped tie bars and steel pipe walls are connected with each other in T-shape in order to enhance the local stability of the walls under pressure. According to the concrete strength C30/C35/C40 and the thickness of the steel plates 1.25mm/1.75mm/2.5mm,42 short-column specimens are made, and the size of all specimens is 200mm×200mm×690mm.The bearing capacity test is done by the 500-ton electro-hydraulic serve testing machine. The strain of U-shaped tie bar and thin-walled steel are tested, and then the whole curve of compression process is obtained. The results show that the U-shaped tie bar has a very good role in bonding, and has good effects on improving buckling mode and the ductility of the components significantly. Concrete-filled thin-walled square steel tube short column fixed U-shaped tie bar has advantages on stronger post- deformability and more applicable to configuration compared with existing research achievements, and can provide a reference for engineering design.

Ultimate Bearing Capacity Analysis of Axially Compressive Circular Steel Tube Columns Filled with Bar-Reinforced Concrete

The mechanical behavior and ultimate bearing capacity of the circular bar-reinforced concrete filled steel tube (BRCFST) short columns under axial compression are analyzed in this paper based on the unified strength theory. Considering the restriction effect of steel tube and hoop bar on concrete, the calculation formula of bearing capacity of the column is deduced. Parametric studies are carried out to evaluate the effects of intermediate principal stresses, diameter-thickness ratio of steel tube and the stirrup ratio on the bearing capacity of the column. A good agreement is reached by comparing the results calculated by the formula with the test results. It is concluded that the unified strength theory is applicable in the theoretical analyses of the BRCFST columns.

Bearing Capacity of Concrete Filled Square Steel Tube Short Columns with Inner CFRP Circular Tube under Eccentric Compression

Based on the unified strength theory, the bearing capacity of the concrete filled square steel tube short columns with inner CFRP circular tube under eccentric compression was analyzed. The restriction effect of the inner CFRP circular tube upon the core concrete, strength reduction factor for eccentricity ratio and the equivalent reduction factor, which considered the ratio of thickness to side effect, were taken into account in the theoretical analysis. The axial bearing capacity formula of the square steel tube short columns filled with inner CFRP circular tube was deduced. By introducing the strength reduction factor for eccentricity ratio, the eccentric bearing capacity formula on the basis of the axial bearing capacity formula was obtained. Parametric studies were carried out to evaluate the effects of intermediate principal stress, different CFRP deployment ratios, eccentricity ratios and the tension-compression ratio on the eccentric bearing capacity of the column. The formula was verified by the comparison of the theoretical results with the experimental data. The results show that inner CFRP circular tube can effectively restrain the core concrete.

Experimental Verification on Bearing Capacity of Concrete-Filled Steel Tube Short Columns Based on Unified Theory

To verify the rationality of calculation method on unified theory of concrete - filled steel tube short columns under axial force, Experimental Study on mechanical properties of the 12 concrete -filled steel tube short columns with 7 different sections under axial force is preformed. Failure process and Failure mode of them are observed, load-displacement curves are obtained, and the influence for confinement coefficient ξ to the mechanical properties of short columns under axial load is analyzed. Based on load-displacement curves, ultimate bearing capacities of them are given. By comparison for ultimate bearing capacity obtained by testing and the bearing capacity according to unified theory, the results show both are in good agreement. Calculation method on unified theory of concrete - filled steel tube is fit for calculating ultimate bearing capacity of short columns under axial force with different sections, and the results are safe and reliable.

Nonlinear Equivalent Simulation of Mechanical Properties of Expansive Concrete-Filled Steel Tube Columns

This paper presents a nonlinear finite element analysis on the behaviour of expansive concrete-filled steel tube (ECFT) short columns. An equivalent model for axially-loaded ECFT columns is proposed. The expansive effect of the core expanding concrete is modeled by applying a temperature field to ordinary concrete. In the elastic stage, the difference between Poisson's ratio for concrete and steel is taken into account. The three dimensional concrete material model (concrete damaged plasticity model) available in ABAQUS, together with the modified Drucker-Prager yielding criterion and the non-associative flow rule are adopted to represent the plastic properties of concrete. By finite element method simulation, the load-deformation curves of the axially-loaded ECFT short columns are obtained. The numerical predictions coincide with the experimental results very well. Meanwhile, the contact pressure between the steel tube and the expansive concrete core, the axial stress distribution in the expansive concrete core under loading and the confining effect of the tube on the expansive concrete core are analyzed.

Recent Findings from Phase V of the United States–Japan Cooperative Earthquake Research Program

Recent Findings from Phase V of the United States–Japan Cooperative Earthquake Research Program