Concrete-filled Double-skin Steel Tube Research Articles

Investigation of Concrete-Filled Double-Skin Steel Tubular Columns with Ultrahigh-Strength Steel

Concrete-filled steel tubular (CFT) columns have been used increasingly in building structures because of their construction efficiency and provision of high stiffness and strength. A relatively new configuration design with inserted inner steel tubes, so-called concrete-filled double-skin steel tubes (CFDSTs), has been developed in the field. To promote the seismic capability of the CFT/CFDST columns further, the authors present results from an experimental investigation of CFT and CFDST columns using ultrahigh-strength steel. Eight scaled column specimens were examined by subjecting them to combined axial and flexural cyclic loadings. The performance of the CFT and CFDST design configurations using high-strength steel was comparable and both provide large moment capacities and elastic deformation capacities. The ultimate member moment capacity could be predicted accurately using a proposed simple formulation based on the concept of the superposed strength method. Various performance parameters are evaluated and discussed, and the influence of compressive strength of the concrete core, applied axial loads, and inserted inner steel tubes on the seismic behavior of the column members is clarified by the experimental results.

Experimental research of seismic behavior and surplus bearing capacity of CFDST under reversed loading

The concrete-filled double skin steel tubes (CFDST) column is a new type of steel composite structure column. At present, international and domestic research are still lacking in regards to this composite structure column. Therefore, a study of the composite structure column would have great theoretical and practical significance. In this paper, an experiment using concrete-filled double skin steel tubes columns with square-circular section is conducted under repeated loading and then under static axial compression. The test results show that the new type of composite structure column has excellent ductility and relatively good surplus bearing capacity. So, the test has laid a certain foundation for doing analysis and study on the new type of composite structure column in the future.

Tensile behaviour of concrete-filled double-skin steel tubular members

Concrete-filled double-skin steel tube (CFDST) a type of steel–concrete composite section which has two concentrically placed steel tubes and concrete filled in between. The CFDST members inherit the advantages of traditional concrete-filled steel tubes and are relatively lighter. They have been used in electric poles and have great potential in other types of structures. This paper in particular presents an experimental study on the concentrically and eccentrically loaded CFDST tensile members. The test parameters include the load eccentricity, the hollow ratio and the nominal steel ratio of the cross section. It is found that the filled concrete works efficiently with the double steel tubes, and provides additional support to the steel tubes under tension. All eccentrically loaded CFDST tensile members exhibit ductile behaviour with end rotation exceeding 0.1rad. Design calculations are also assessed. The results indicate that the existing design proposal for CFDST tensile member has to be improved.

Finite Element Analysis of Concrete Filled Double-Skin (CHS Inner and CHS Outer) Steel Tubes under Lateral Impact

As a new type of steel-concrete composite structure, Concrete-Filled Double Skin Steel Tubes not only have the advantages of the traditional steel concrete structures, but also carried out cross-section and great bending stiffness. This structure is widely used in high-rise buildings, bridges and power facilities. During the whole life cycle, concrete-filled double skin steel tubes may inevitably suffer from various impact loads. In current the research about steel-concrete composite structure focuses on the performance about axial compression, bias, bending, and low cyclic loads. but the research about it under lateral impact is equally import. In this paper, the behavior of concrete-filled double skin steel tubes (CFDST) with fixed boundary condition was analyzed by Finite Element Analysis method ,to analyze the destruction modal, impact force (F) , deflection () as well as other dynamic responses of CFDST under different lateral impact energy. The work mechanic and full range analysis of concrete filled double steel tube under lateral impact were analyzed. The results show that the damage of CFDST with fixed boundary condition under lateral impact is in ductile manner. Analyzed the whole process of the dynamic response basically , laid the foundation for further parametric analysis and practical calculation method.

超高強度鋼H-SA700を用いた中空CFT柱部材の曲げ圧縮性能

Concrete filled steel Tubes (CFTs) have been used increasingly for providing large stiffness and strength. Many studies were conducted on CFT columns, and a new configuration design with the concrete filled double-skin steel tubes (CFDSTs) was also developed. This paper presents an experimental investigation on CFT and CFDST columns using ultra-high strength steel. Six specimens with various dimensions and types of steel were tested by combined axial and lateral loading. Influences of those design parameters on the seismic behavior of CFTs and CFDSTs, i.e. initial stiffness, ultimate moment, strength deterioration, local buckling and fracture failure, were investigated.

Investigation on concrete filled double skin steel tubes (CFDSTs) under pure torsion

This paper presents a series of tests on concrete filled double skin steel tubular (CFDST) members subjected to pure torsion. Two types of combinations are included, i.e., CFDST section with circular hollow section (CHS) as both inner and outer tubes, and section with CHS as the inner tube and square hollow section (SHS) as the outer tube. Finite element method was used to analyze typical failure mode and complete torque–rotation curve of the specimens, as well as interaction between the steel tubes and the sandwiched concrete of CFDSTs. It was found that the results calculated by finite element method show reasonable agreement with those of the test results. Six important parameters influencing the torque versus torsional rotation curves are identified, i.e. nominal steel ratio, yield strength of outer steel tubes and inner steel tubes, concrete cube compressive strength, width to thickness ratio of inner steel tubes and hollow section ratio. Finally, design formulas are proposed for calculating torsional capacities of CFDSTs.

Finite Element Analysis of Concrete-Filled Double Skin Steel Tubes with Simply Supported under Lateral Impact

In this paper, the behavior of concrete-filled double skin steel tubes (CFDST) with simply supported boundary condition was analyzed by Finite Element Analysis method. The Finite Element analysis mode was established and the results have a good consistent with experimental results. The work mechanic and full range analysis of concrete filled double steel tube under lateral impact were analyzed, the results show that the damage of CFDST with simply supported boundary condition under lateral impact is in ductile manner.

Experimental behaviour of partially loaded concrete filled double-skin steel tube (CFDST) sections

The experimental behaviour of concrete filled double-skin steel tube (CFDST) sections subjected to partial compression is reported in this paper. Fourteen specimens with outer and inner steel tubes of circular hollow section (CHS) and fifteen specimens with outer and inner steel tubes of square hollow section (SHS) were tested. The test parameters included: 1) hollow ratio, 2) top endplate thickness, and 3) partial compression area ratio. The test results indicated that the CFDST columns under partial compression behaved in a ductile manner. The partial compressive behaviour and the failure modes of partially loaded CFDST stub columns were significantly affected by the parameters investigated. Finally, a simplified model for predicting the bearing capacity of partially loaded CFDST sections is proposed.

Concrete-filled double skin steel tubular (CFDST) columns subjected to long-term sustained loading

This paper carried out a series of tests on concrete-filled double skin steel tubes (CFDST) columns under long-term sustained loading condition. The test process included two stages, i.e. long-term service test and ultimate strength test. Numerical models on analysis of the CFDST column under long-term sustained loading were presented. A comparison of results calculated using these models showed generally good agreement with the test results. Additionally, a detailed analysis was performed to analyse the long-term behaviour of CFDST columns. Finally, simplified formula for calculating the ultimate strength of CFDST columns subjected to long-term sustained loading was proposed.

Analytical behaviour of concrete-filled double skin steel tubular (CFDST) beam-columns under cyclic loading

Concrete-filled double skin steel tubes (CFDST) have a great potential to be used in the construction of bridges and buildings. Limited information is available on the models for the moment ( M) versus curvature ( φ) response, and the lateral load ( P) versus lateral displacement ( Δ) relationship of these columns subjected to axial load and cyclically increasing flexural loading. A mechanics model is developed in this paper for CFDST beam-columns subjected to constant axial load and cyclically increasing flexural loading. The predicted cyclic responses for the composite columns are in good agreement with test results. Based on the theoretical model, parametric analysis was performed on the behaviours of moment ( M) versus curvature ( φ) response and lateral load ( P) versus lateral displacement ( Δ) relationship for the composite columns. Finally, simplified models for the moment ( M) versus curvature ( φ) response, and the lateral load ( P) versus lateral displacement ( Δ) relationship were suggested.

Behavior of concrete-filled double skin steel tubular columns with octagon section under axial compression

Based on some conclusions of two kinds of concrete-filled double skin steel tube (CFDSST) members with circular or square sections, a new kind of CFDSST with octagonal section, where the outer tube has an octagonal section and the inner tube has a circular section, is proposed in this paper. Behaviors of the CFDSST members with octagon section subjected to axial compression are investigated, and some curves of load-strain of steel tubes and confined concrete and the bearing capacity of members are obtained. It is indicated that the bearing capacity of the columns with octagonal section is larger than that with square section and is smaller than that with circular section, and the bearing capacity of members is related to the ratio of the straight side to the bevelled one. Based on the proper stress-strain relationship, a couple of numerical analyses are made using the finite element software named ANSYS. Finally, a simplified formula is proposed in the paper, and the numerical results agree well with the experimental results and the mathematical solutions. The results are valuable for engineers.

Concrete-filled double skin steel tubular (CFDST) beam–columns subjected to cyclic bending

In recent years, it was proposed by several researchers that concrete filled double skin steel tubes (CFDST) be studied for their strength as a column or a beam. Advantages of CFDST over fully concrete filled steel tubes (CFST) include: increase in section modulus; enhancement in stability; lighter weight; better damping characteristics and better cyclic performance. It is thus expected that concrete filled double skin steel tubes (CFDST) have the potential of being used in building structures. This paper provides new test data pertaining to the seismic behavior of CFDST beam–columns. The test parameters included the section types (circular and square), the core concrete strength ( f cu ) , and the axial load level ( n ) . Twenty-eight CFDST column specimens, including 16 specimens with SHS (square hollow section) outer and CHS (circular hollow section) inner, 12 specimens with CHS (circular hollow section) outer and CHS (circular hollow section) inner were tested under constant axial load and cyclically increasing flexural loading. The CFDST beam–columns were found to have significant increase in strength, ductility, and dissipated energy over the outer jackets. In general, the ductility and energy dissipation ability of specimens with circular sections are higher than those of the specimens with square sections. The mechanics model which was developed by the authors for concrete filled steel tubular (CFST) beam–columns subjected to constant axial load and cyclically increasing flexural loading, is used to analyze the behavior of CFDST beam–columns. It is found that the predicted cyclic responses for the composite beam–columns are generally in reasonable agreement with test results. Finally, comparisons are made with predicted beam–column flexural stiffness using the existing codes.