Concrete-filled Steel Tube Beam-columns Research Articles

Cyclic loading tests of thin-walled square steel tube beam-column joint with different joint details

To study the seismic performance of a thin-walled square steel tube beam-column joint of a light steel frame, 8 kinds of thin-walled square-hollow structural steel (HSS) and concrete-filled steel tube (CFST) beam-column joints with different joint details were designed and manufactured. The joint details were divided mainly into welded joint, plate joint, angle joint and angle with stiffener joint. A total of 14 specimens of beam-column joint specimens were tested using a low reversed cyclic loading test. The failure characteristic, load-bearing capacity, hysteretic property, stiffness degradation and energy dissipation were compared. The results showed that the different joint details had a great influence on the seismic performance of the beam-column joint. The bearing capacity and failure rotation of the welded joint were poor. The bearing capacity of the plate joint was close to that of the welded joint, but it showed improved bearing capacity, failure rotation and energy dissipation capacity of the joint. The bearing capacity of the angle joint was poor. With the angle welded stiffener, the bearing capacity, stiffness and energy dissipation capacity of the joints were significantly improved. The number and height of the stiffener can improve the seismic performance of the joint. The stiffness and energy dissipation capacity of the CFST beam-column joint was better than that of the HSS beam-column joint with the same joint detail. The classification of the joint is discussed, and a simplified M-R calculation model is proposed.

Analysis and Design of Noncompact and Slender CFT Beam-Columns

Concrete-filled steel tube (CFT) beam-columns are categorized as compact, noncompact, or slender depending on the governing slenderness ratio (width-to-thickness b/t or D/t ratio, λ) of the steel-tube wall. The current AISC specification recommends the bilinear axial force-bending moment (P−M) interaction curve for bare steel members for the design of noncompact and slender CFT beam-columns. This paper compiles the experimental database of tests conducted on noncompact and slender CFT beam-columns, and demonstrates the overconservatism of the AISC P−M interaction curve. This paper also presents the development and benchmarking of detailed 3D finite-element models for predicting the behavior and strength of noncompact and slender CFT members. The benchmarked models are then used to evaluate the fundamental P−M interaction behavior of CFT beam-columns, and the influence of material and geometric parameters such as the tube slenderness ratio (λ), material strength ratio (Fy/fc′), member length-to-section depth ratio (L/D), and axial load ratio (P/Po). The parametric analyses indicate that for L/D ratios up to 20, the P−M interaction curves are governed by the relative strength ratio (csr=AsFy/Acfc′). The parametric analysis results are used to propose revisions to the current standard’s interaction equations for designing noncompact and slender CFT beam-columns.

Fundamental behavior of CFT beam-columns under fire loading

This paper presents experimental investigations of the fundamental behavior of concrete filled steel tube (CFT) beam-columns under fire loading. A total of thirteen specimens were tested to determine the axial force-moment-curvature-temperature behavior of CFT beam-columns. The experimental approach involved the use of: (a) innovative heating and control equipment to apply thermal loading and (b) digital image correlation with close-range photogrammetry to measure the deformations (e.g., curvature) of the heated region. Each specimen was sequentially subjected to: (i) constant axial loading; (ii) thermal loading in the expected plastic hinge region following the ASTM E119 temperature-time T-t curve; and (iii) monotonically increasing flexural loading. The effects of various parameters on the strength and stiffness of CFT beam-columns were evaluated. The parameters considered were the steel tube width, width-tothickness ratio, concrete strength, maximum surface temperature of the steel tube, and the axial load level on the composite CFT section. The experimental results provide knowledge of the fundamental behavior of composite CFT beam-columns, and can be used to calibrate analytical models or macro finite element models developed for predicting behavior of CFT members and frames under fire loading.

Use of Neural Networks to Predict Ultimate Strength of Circular Concrete Filled Steel Tube Beam-Columns

Use of Neural Networks to Predict Ultimate Strength of Circular Concrete Filled Steel Tube Beam-Columns

Damage evaluation of composite-special moment frames with concrete-filled tube columns under strong seismic loads

Concrete Filled steel Tube (CFT) columns have been widely used in moment resisting frame structures located on non-seismic zones or high seismic zones. This paper discusses the design of such composite members based on the advanced methods which are introduced in the 2005 America Institute of Steel Construction (AISC) Specification and the 2005 AISC Seismic Provisions. These design specifications explicitly allow the use of the full plastic capacities of CFT columns, and so they require column members with more slender steel walls than ones allowed in previous specification. In addition, this study focuses particularly on damage evaluation following nonlinear frame analyses. The paper begins with an examination of design interaction curves including the length effect and the full plastic strength demand in CFT beam-column members. Based on advanced computational simulations of a series of 3-, 9-, and 20-story SAC composite-special moment frames, this paper then investigates new techniques to evaluate the damage of CFT columns during a strong earthquake. The paper concludes with some discussion of (a) step by step procedures to compute the interactive ratios of the individual CFT beam-columns and (b) member vs. seismic performance evaluation.

Predicting Fire Behavior of Composite CFT Columns Using Fundamental Section Behavior

Abstract This paper presents the development and verification of a fiber-based analytical approach for predicting the behavior of concrete filled steel tube (CFT) columns subjected to constant axial load and standard fire loading. The approach consists of three parts: (1) Two-dimensional heat transfer analysis, (2) section moment-curvature analysis, and (3) column inelastic buckling analysis using modified Newmark’s method. The analytical approach was verified by using it to predict (1) the thermal and structural behavior of CFT column specimens subjected to standard fire tests by different researchers and (2) the fundamental moment-curvature behavior of CFT beam-column specimens subjected to special (non-standard) fire tests conducted by the authors. The analytical approach predicts the fundamental moment-curvature behavior of CFT beam-column specimens and the standard fire behavior of CFT column specimens with reasonable accuracy. The analytical results also compare favorably with the overall behavior and stress states predicted by three-dimensional finite element analyses conducted earlier by the authors. The fiber-based analytical approach is recommended for modeling and predicting the standard, non-standard, or realistic fire behavior of CFT columns and beam-columns under various loading, heating, and boundary conditions.

Development and Validation of Fiber Model for High-Strength Square Concrete-Filled Steel Tube Beam-Columns

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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

Seismic Behavior and Design of High-Strength Square Concrete-Filled Steel Tube Beam Columns

The behavior of high strength square concrete filled steel tube (CFT) beam columns subjected to constant axial load and cyclically varying flexural loading was investigated experimentally. The effe...

Closure to “Experimental Behavior of High Strength Square Concrete-Filled Steel Tube Beam-Columns” by Amit H. Varma, James M. Ricles, Richard Sause, and Le-We Lu

Closure to “Experimental Behavior of High Strength Square Concrete-Filled Steel Tube Beam-Columns” by Amit H. Varma, James M. Ricles, Richard Sause, and Le-We Lu

Discussion of “Experimental Behavior of High Strength Square Concrete-Filled Steel Tube Beam-Columns” by Amit H. Varma, James M. Ricles, Richard Sause, and Le-Wu Lu

Discussion of “Experimental Behavior of High Strength Square Concrete-Filled Steel Tube Beam-Columns” by Amit H. Varma, James M. Ricles, Richard Sause, and Le-Wu Lu

Concrete-filled steel tube columns under earthquake loads

Concrete-filled steel tubes (CFTs) have been used throughout the world in structures of varying heights and structural configurations, both in non-seismic and in high seismic zones. This review summarizes the behavior of circular and rectangular concrete-filled steel tube beam-columns and braces, particularly focused on their behavior when subjected to cyclic seismic loading. It begins with a discussion of the monotonic behavior of CFTs subjected to axial, flexural, and torsional loading, and summarizes the effects on CFT behavior of creep, shrinkage, composite action and residual stresses. The synopsis of monotonic behavior provides a basis for the subsequent discussion of research on the cyclic behavior of CFTs. The article concludes with a summary of publications in which current CFT design provisions are outlined for several non-seismic and seismic specifications throughout the world.

超高強度コンクリート充填鋼管せん断曲げ柱の終局挙動に関する実験的研究

To investigate the ultimate behavior of high-strength concrete filled steel tube (CFT), dynamic loading test of CFT beam-columns has been carried out. The test results exhibit that the maximum strength of every specimen is larger enough than the ultimate strength predicted by the generalized superposed strength method but the ratio of them changes according to the relation between the strength of steel tube and filled concrete. It is also shown that there are two kinds of ultimate state which are the crack development in steel tube and the excessive accumulation of plastic axial deformation and special attention should be paid to the former ultimate state because it is brittle fracture in the case that CFT is filled with high-strength concrete and subjected to dynamic load.

A distributed plasticity model for concrete-filled steel tube beam-columns with interlayer slip

A fiber-based distributed plasticity finite element formulation is presented to perform three-dimensional monotonic analysis of square or rectangular concrete-filled steel tube (CFT) beam-columns. This stiffness-based beam-column element fomulation accounts comprehensively for all significant geometric nonlinearity exhibited by CFT beam-columns as part of composite frame structures, and the steel and concrete constitutive models account for the significant inelastic phenomena which are seen in CFT experiments. In addition, the finite element formulation accounts for slip between the steel and concrete components of the CFT by incorporation of a nonlinear slip interface. This formulation is able to capture behavior ranging from perfect bond to immediate slip. The calibration and verification of the slip formulation are presented, and the finite element model is verified against experiments of CFT beam-columns subjected to monotonic loading. Results from a preliminary study are presented on the effect of slip on CFT beam-column and composite frame behavior. A related paper extends this formulation to cyclic analysis of composite CFT frames, and provides details of the steel and concrete constitutive models.

A distributed plasticity model for cyclic analysis of concrete-filled steel tube beam-columns and composite frames

This paper presents the constitutive formulation and cyclic analysis capability of a three-dimensional fiber-based distributed plasticity finite element for square or rectangular concrete-filled steel tube (CFT) beam-columns. A related paper outlines the geometrically nonlinear formulation and the element's formulation for interlayer slip between the steel tube and concrete core. The present paper discusses the steel and concrete cyclic material models, which are each based on stress-space bounding-surface plasticity formulations. The paper details the calibration of these models to steel coupon tests and to experiments of short CFTs in flexure which yield moment-curvature-thrust results. Verification of the model is provided by comparing to several experiments of CFT beam-columns loaded monotonically and cyclically, proportionally and nonproportionally, and in single and reverse curvature. A final example presents a comparison of the analysis to the experimental results of a composite subassemblage consisting of three steel I-girders framing rigidly into a CFT beam-column, which is thus subjected to axial force plus cyclic biaxial bending.

A Cyclic Nonlinear Model for Concrete-Filled Tubes. I: Formulation

This paper presents a three-dimensional (3D) cyclic nonlinear finite-element model for concrete-filled steel tube (CFT) beam-columns and composite frame structures. This CFT beam finite element is incorporated into a matrix analysis program suitable for conducting monotonic static, cyclic static, or transient dynamic seismic analyses of complete composite unbraced frame structures composed of steel I-girders framing biaxially into CFT beam-columns. The material formulation consists of a concentrated plasticity bounding surface model in 3D stress-resultant (force) space. A polynomial expression developed in previous work to represent CFT cross-section strength is incorporated into this material model to represent the force-space yield surfaces. In addition, new formulations are present for isotropic and kinematic hardening of the loading and bounding surfaces to model strength degradation and stiffness deterioration of CFTs subjected to cyclic loading. Part II of this two-part paper presents the calibration and verification of the CFT element. This formulation is verified against a comprehensive set of experimental data and is accurate for a wide range of CFT cross-section sizes and material strengths.

Representation of Concrete-Filled Steel Tube Cross-Section Strength

This paper presents the development of a polynomial equation to represent the three-dimensional (3D) cross-section strength of square or rectangular concrete-filled steel tube (CFT) beam-columns. The equation provides an accurate representation of the cross-section strength of a CFT subjected to a combination of axial force, strong axis flexure, and weak axis flexure. This expression is verified against the results of a detailed fiber analysis formulation, and against experimental tests of short, square CFTs available in the literature. This CFT cross-section strength equation forms a compact expression of the failure surface of square or rectangular CFTs having a wide range of cross-section dimensions and material strengths. The cross-section strength surface also provides the basis for a bounding-surface concentrated plasticity model in 3D force space for CFT beam-columns, presented in related work by the writers. This beam-column model, in turn, is suitable for conducting monotonic static, cyclic static, or transient dynamic seismic analysis of complete composite unbraced frame structures composed of steel I-girders framing biaxially into CFT beam-columns.