Concrete-filled Square Steel Tube 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.

STUDY ON COMPRESSIVE BEARING CAPACITY OF CONCRETE-FILLED SQUARE STEEL TUBE COLUMN REINFORCED BY CIRCULAR STEEL TUBE INSIDE

This paper concentrates on the compressive bearing capacity of one composite column of a Concrete-Filled Square Steel Tube (CFSST) reinforced by a circular steel tube inside. Some tests were conducted to consider the compression behaviour of the stub columns under axial compressive loading. Through an elastoplastic limit analysis based on Unified Strength Theory (UST), the ultimate load capacity of the CFSST columns reinforced by inner circular steel tube under axial compression has been derived, which has a good agreement with the experimental results in comparison with other empirical models. So this model is extended to predict the optimal design of the inner tube, namely, Di/ti and Di/B. In addition, another simple model is also proposed to testify the optimal section of this composite column. With the optimal circular steel tubes inside the CFSST column, the composite column can result in significant savings in column size, which ultimately can lead to significant economic savings and higher bearing capacity. The results show that it has a theoretical significance and application value to adopt circular steel tube to strengthen CFSST column.

Nonlinear Analysis on Static Behaviors of New All-Bolted Beam-to-Column Connections for Concrete-Fillled Square Steel Tube

All-bolted steel beam-to-column connections for concrete-filled square steel tube (CFST) have the advantages of industry manufacture, being constructed quickly and easily concreting. The new design all-bolted connection discussed in this paper has the construction details of Π-shape plate and high strength bolts which connect the steel beam and CFST column. In order to investigate the static performances and failure modes of this new all-bolted connection, a full three-dimension ANSYS finite element (FE) model of the connection subjected to montonic load is built up. The theoretical values and experimental results are very close, that verifies the rationality of the FE models and the analysis method in this research. Further the calculated results demonstrated the new bolted connections belong to typical semi-rigid connection and have the superior static resistance in stiffness, strength, and rotating capacity.

Study on Finite Element Method for Simulating Seismic Behavior of New All-Bolted Semi-Rigid Connection

Using the APDL language of ANSYS which is the large general-purpose finite element software, the finite element (FE) model of new bolted beam-to-column connection for concrete-filled square steel tube (CFST) is established. The simulated analysis for the seismic behavior of the new semi-rigid connection under low-cycle reverse loading is carried out by the FE method. It is focus on the method study on establishing geometry model, selection of element and its parameter, setting up boundary restraint and solution during FE analysis. Through comparision it is found that the calculated values and the experimental results are very close, which verifies the correctness and rationality of the method in this paper. The research work provides fundamental basis for future intensive study on seismic behavior of the new connection.

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.

Behavior of New Type of Semi-Rigid Joints under Moment and Tensional Force

In the system of preventing progressive collapse, the joints always play a key role in catenary action and alternate load path while the joints are usually under the combination of bending moment and tensional force. In this combination, high rotation capacity and good resistance of joints are demanded. In this paper, a new type of semi-rigid joint used in the structures with concrete-filled square steel tube (CFST) columns is proposed and developed by ABAQUS. The new type joint is suitable for the classification for semi-rigid connection; The bending moment resistance of the joint decreases linearly with the increase of tensional force; reducing pretension force reasonably is beneficial for the tensional force to develop “catenary action”; the width of short leg of angle would influence the moment resistance of the joint evidently; the initial rotation stiffness is not affected by width of leg dramatically.

Nonlinear Finite Element Analysis on Seismic Behavior of Concrete Filled Square Steel Tube Planar Frames

This paper presents a nonlinear numerical analysis on the seismic behavior of concrete filled square steel tube (CFST) columns and steel beam planar frame with through bolt-endplate beam-column connection, by using the finite element analysis modeling with ABAQUS. Parametric studies were conducted to investigate the influence of axial load ratio and beam-to-column linear stiffness ratio on the seismic behavior of composite frames. The analysis results were in good agreement with the experiment results. The analysis results showed that CFST frame with through bolt-endplate beam-column connection had good seismic behavior. The increase of axial load ratio will degrade the horizontal load bearing capacity and increase the energy dissipation capability. The increase of beam-to-column linear stiffness ratio will increase the horizontal load bearing capacity and degrade the energy dissipation capability.

Nonlinear Finite Element Analysis on Seismic Behavior of Concrete Filled Square Steel Tube Planar Frames

This paper presents a nonlinear numerical analysis on the seismic behavior of concrete filled square steel tube (CFST) columns and steel beam planar frame with through bolt-endplate beam-column connection, by using the finite element analysis modeling with ABAQUS. Parametric studies were conducted to investigate the influence of axial load ratio and beam-to-column linear stiffness ratio on the seismic behavior of composite frames. The analysis results were in good agreement with the experiment results. The analysis results showed that CFST frame with through bolt-endplate beam-column connection had good seismic behavior. The increase of axial load ratio will degrade the horizontal load bearing capacity and increase the energy dissipation capability. The increase of beam-to-column linear stiffness ratio will increase the horizontal load bearing capacity and degrade the energy dissipation capability.

LOCAL ELASTO-PLASTIC BEHAVIOR OF STEEL BEAM TO CONCRETE-FILLED SQUARE STEEL TUBE COLUMN MOMENT CONNECTIONS USING ELECTROSLAG WELDING

Subassemblage tests were conducted on steel beam to concrete filled square steel tube (CFT) column moment connections to investigate the structural behavior of electroslag welding connections between internal diaphragms and steel tube. The writers propose an ultimate strength equation for these connections, based on combined stresses on a fracture line within the steel plate of the CFT column. They have already proposed a model for a load-displacement relation for predicting the local tensile elasto-plastic behavior of CFT column to steel beam moment connections using internal diaphragms. This paper proposes an improved load-displacement relation model for these connections including an ultimate strength equation for electroslag welding connections in the load-displacement relation model. The improved model is found to agree approximately with this experimental result up to large deformations.

高強度材料を用いたコンクリート充填角形鋼管短柱の二軸曲げ性状

In this study, the effects of loading direction on the flexural behavior of concrete filled square steel tube (CFT) are experimentally studied. The selected test parameters are loading direction and eccentricity of axial load. As the result, It was indicated that the flexural stiffness and axial stiffness of CFT column subjected to bi-axial bending could be evaluated by the equivalent stiffness of the concrete elastic stiffness with that of the steel tube regardless of the loading direction, the same as the case under the uni-axial bending. The ultimate strength curve of CFT column subjected to the bi-axial bending was ascertained, and its evaluation formula was proposed.