Concrete-filled Square Research Articles

Experimental Behavior of Concrete-Filled Square Steel Tube of Mid and Long Columns Subjected to Eccentric Compression

This paper presents an experimental investigation of the mechanic behavior of 9 concrete-filled square steel tube columns (CFSST) subjected to eccentric loading. The primary parameters of the specimens are eccentricity ratios, slenderness ratios and concrete strength. The results showed that the eccentricity ratios and slenderness ratios are the primary factors to influence the load-bearing capacity of CFSST columns, with the increase of eccentricity ratios and slenderness ratios, the limit load-bearing capacity reduced gradually. The influence of concrete strength to load-bearing capacity decreased gradually with the increase of eccentricity ratios and slenderness ratios.

Research on Seismic Behavior of Concrete Filled Square Tubular Joints with Reduced Beam Section under Cyclic Loading

The 3D nonlinear FEM models of concrete-filled square tubular column with internal diaphragms and steel beams with reduced beam section bolt-weld joints, involving geometric, materials and contact nonlinear were founded. The results of FEM are agreed to that of tests, so we can conclude that FEM in this paper is correct. Then the bearing capacity behavior of joints under cyclic loading are analyzed, including P-Δskeleton curves, P-Δ hysteretic curves, the dissipating energy ability and destruction form. The analysis results show that the plastic hinge in the joint with reduced beam section is removed to the reduced beam region. The joints that studied in this paper present excellent ductility and dissipating energy ability, therefore, all of them have a good seismic behavior.

Responses of Concrete-Filled Cold-Formed Square Hollow and Double-C Steel Stub Columns under Cyclic and Repeated Loadings

This paper presents an experimental study on the response of 18 concrete-filled cold-formed square hollow and double-C steel stub columns under cyclic and repeated loading. The test parameters were (1) infilled materials, i.e. No fill, concrete infilled and mortar infilled columns (2) cross sectional shape and dimension. The effect of lips in double-c section as inside stiffeners is presented. The cyclic tested results indicate the infilled columns possess higher bearing capacity, especially infilled materials with higher strength and non-compact section columns. However, there is no different in ultimate tensile. Moreover, the infilled columns showed larger area under post-yield hysteretic loops leading to better seismic performance. Failure of columns was modified in which the failure mode was shifted from the in-outward local buckling into the outward manner, consequently resulted to higher bearing capacity.

Capacities of Concrete-filled Steel Beams of Unequal Double Spans by Testing and Code

This paper presents an experimental investigation on flexural capacity of square hollow section (SHS) steel and concrete-filled square hollow section (SHS) steel tube. Beams with unequal double spans and subjected to point loads at the middle of each span were tested. Comparison was made on the flexural capacity and ductility of bare SHS steel and concrete-filled SHS steel tubes. The moment capacities obtained by the design method in code of practice for structural uses of steel 2005 – CoPHK were compared with experimental results reported in this paper.

Seismic Performance of Concrete-Filled Square Tubular Column and Reduced Steel Beam Joints

According to anti-seismic design principle of strong column and weak beam, and of strong joint and weak member, reduced beam section (RSB) is often used to shift away plastic hinge from end of beam to the weaken region of the beam. The non-linear finite element models are established for concrete-filled steel square tubular column and reduced steel beam with holes in flange or in flange and web, considering geometric large deformation and material nonlinear. Comparison is made on load-displacement curves, the stress distribution of reduced beams, the ultimate load-carrying capacity, the ductility, and the energy-dissipating ability between analysis results of different RBS joints and experimental results. It shows that the stiffness and ultimate load-carrying capacity of new RBS joints are close to traditional RBS joint, the plastic hinge in the new joints with reduced beam section can be moved to the reduced region, and the new joints display good ductility, energy-dissipating ability and seismic behavior.

Parametric Analysis on Seismic Behavior of Connections to Concrete-Filled Square Steel Tubular Columns with Three Edges Welded Interior Diaphragm

In order to further understand the seismic behavior of connections to concrete-filled square steel tubular columns with three edges welded interior diaphragm, basic sample and corresponding finite element models are constructed and analyzed according to criterion; furthermore influences on seismic behavior of such connections from many factors such as axial load ratio, height of steel beam, strength of steel beam and interior diaphragm and so on are studied. Results show that the base sample has excellent seismic behavior; such factors as axial load ratio, height of steel beam, strength of steel beam and interior diaphragm have great influence on seismic behavior. Therefore, the feasibility of such connections at edge columns and corner columns is further validated.

Study on Mechanical Behavior of Concrete-Filled Square Tubular Column and Bolt-Weld Steel Beam Joints with Reduced Beam Section

The nonlinear FEM models of concrete-filled square tubular column with internal diaphragms and steel beams with reduced beam section bolt-weld joints, involving geometric, materials and contact nonlinear, were established. The 3D models of beam-to-column joints with internal diaphragms by 3D solid elements are founded. The bearing capacity behavior of joints under the monotonic loading are analyzed, including P-Δ curves, the stresses distribution of beam, the dissipating energy ability and destruction form. The analysis results show that the initial stiffness of joint with reduced beam section is close to that of non-reduced beam section joint. The bearing capacities of joints with reduced beam section are lower a little than that of non-reduced beam section joint. The plastic hinge in the joint with reduced beam section is removed to the reduced beam region.

Research on Hysteretic Behavior of the Concrete Filled Square CFRP-Steel Tubular (S-CFRP-CFST) Beam-Columns (I): Experimental Study

Overall 12 specimens were experimentally investigated in this paper to study the hysteretic behaviors of the concrete-filled square CFRP-steel tubular (S-CFRP-CFST) beam-columns. The test results indicated that CFRP can provide transverse confinement effect and longitudinal strengthening effect for the concrete filled square steel tubular (S-CFST) beam-columns effectively and the local buckling of the steel tube is deferred. The hysteretic load-deflection curves and the hysteretic moment-curvature curves at the mid-span of all the specimens are generally plump, and it shows these specimens have good hysteretic performance. In the later loading period, the load bearing capacity drops.

Experimental Research on the Confinement Effect for the Composite Concrete-Filled Square Steel Tubular Short Columns

Through the axial compression tests of two ordinary concrete-filled square steel tubular(CFSST) short columns and six composite CFSST short columns, the influence laws of section types, confinement coefficient, steel ratio and concrete strength on the mechanical behavior of the CFSST short columns were studied. The results show that in CFSST columns, the change of steel tube’s section form can improve effectively the cooperative work ability between the steel tube and core concrete, enhance the restraint effect of the steel tube on the core concrete, delay or inhibit the development of inclined cracks in the core concrete, increase the ductility and improve significantly the ultimate bearing capacity when the steel ratio or confinement coefficient is close to each other. With the increment of the confinement coefficient and steel ratio, the bearing capacity and ductility improve.

Shape Optimization and Seismic Design of Concrete-Filled Square Tubular Column and Reduced Beam Section with Cut Web

According to anti-seismic design principle of strong column and weak beam, and of strong joint and weak member, reduced beam section(RBS) is often used to shift away plastic hinge from end of beam to weaken region of the beam. Reduced beam section with cut web are analyzed by non-linear finite element method(FEM) in this paper. Two kinds of effective suggested joints of reduced beam section(circled hole and long-circled hole) are put forward by comparing the results of mechanical behavior of reduced beam section with which of traditional RBS, including of ultimate load-carrying capacity, Von-mises stress distribution and the place of largest stress of beam end of the beam-column joints. A proposed seismic design method is put forward according to related chinese codes.

Axial Strength of Concrete-Filled Square Steel Tubular Columns Reinforced by Inner Circular Steel Tube

This paper presents the theoretical and experimental results of concrete-filled steel tube columns subjected to axially compression. A total of 6 specimens with outer square sections reinforced by inner cicular steel tube were constructed for experimental investigation. The ultimate strengths of the columns from tests were obtained. The theoretical strengths of the columns were also investigated based on unified strength theory, and compared with the test results. Good agreement can be observed from the comparison.

Experimental Study on SNCF of Welded CHS-CFSHS T-Joints under Axial Loading

The initiation position can be predicted by studying on strain concentration factors (SNCF) and SNCF distributions. This paper concerns an experimental investigation of SNCF of welded T-joints composed of circular hollow section (CHS) braces and concrete-filled square hollow section (CFSHS) chords under axial loading on the braces with two load cases of tension and compression. Static experiments were performed on eight test specimens designed for considering different non-dimensional geometric parameters and C50 grade concrete. Compared with joints made of CHS-SHS, the experimental results indicate that the CHS-CFSHS T-joints have lower strain concentration factors which may increase fatigue strength. The position of the maximum SNCF is usually located at 00 or 900 of the intersection line between a CHS brace and a CFSHS chord.

Response of Foam- and Concrete-Filled Square Steel Tubes under Low-Velocity Impact Loading

This paper presents the results of experimental and numerical studies of the comparative behavior of square hollow section (SHS) tubes filled with rigid polyurethane foam (RPF) and concrete undergoing transverse impact loading. A series of instrumented drop hammer tests were performed on mild steel and stainless steel SHSs for both filled and unfilled constructions. The concrete-filled tubes had the highest impact resistance and energy absorption capacity, followed by the steel tubes filled with RPF, and then the hollow tubes. The results also show that RPFs can be used as an effective infill material in structural steel hollow columns when expedient enhancement of the energy absorption capacity is required, e.g., to increase blast and impact resistance of hollow structural elements. Nonlinear dynamic finite-element analyses were carried out to simulate drop hammer test conditions. The predicted impact forces, deformation histories, and failure modes were found to be in good agreement with the experimenta...

Cumulative limit axial load for concrete-filled square steel tube columns under combined cyclic lateral and constant axial load

This paper presents and discusses the results of parametric analyses on the relationship between the axial force and the deformation capacity of concrete-filled square steel tube (square CFT) columns using the developed nonlinear fiber element method. The accuracy of the computational technique is verified by comparing the results from this technique with experimental results carried out by Matsuiet al., 1998. The developed computational technique is used to investigate the cumulative limit axial load for square CFT column by parametric studies and compare with the limit axial load developed by Matsuiet al., 1998 on the basis of experimental data. Formula suitable for the calculation of the cumulative limit axial load of square CFT columns is presented.

Axial compression stability of a crisscross section column composed of concrete-filled square steel tubes

A crisscross section column composed of concrete-filled square steel tubes was tested in axial loading up to failure. The column was analyzed by the finite element method and the ultimate load as well as the failure mode were in agreement with the experimental findings. An analytical method was also proposed which when applied to the tested column gave an estimate of the ultimate load about 4% different from the experimental. The analytical method also predicted the mode of failure correctly.

A study on the seismic performance of concrete-filled square steel tube column-to-beam connections reinforced with asymmetric lower diaphragms

This paper studies the development of the through-type concrete-filled square steel tube column-to-beam connection, reinforced with an asymmetric lower diaphragm. This type of connection can be used in weak-earthquake regions such as Korea. A simple tension test was performed on the suggested lower diaphragms and the combined cross diaphragm in order to confirm their tensile behavior. Subsequently, four types of concrete-filled square steel tube column-to-beam connection (with combined cross diaphragm, nothing, horizontal T-bar and vertical plate as lower diaphragm) were fabricated in actual size and tested according to the ANSI/AISC SSPEC 2002 cyclic loading program. The horizontal T-bar and stud bolts in the vertical plates were designed to transmit the tensile stress from the bottom flange of the beam to the filled concrete. All the test specimens satisfied the 0.01 radian inelastic rotation capacity requirements for the composite ordinary moment frame (C-OMF) of the AISC seismic provisions. It was concluded that the suggested simplified lower diaphragms have sufficient strength, stiffness and plastic deformation capacity to be used in the field.

Analysis and design of concrete-filled stiffened thin-walled steel tubular columns under axial compression

Longitudinal stiffeners are effective in improving the overall performance of concrete-filled square or rectangular thin-walled steel tubular columns. This paper is concerned with the nonlinear analysis and design of stiffened square stub columns under axial compression. The nonlinear analysis is performed using ABAQUS, a commercially available finite element (FE) program. Close agreement is shown between the test and predicted results in terms of the load-deformation curves and ultimate strength. The column behaviour is investigated and discussed using this modelling. The limit of width-to-thickness ratio for the sub-panels and the rigidity requirement for the stiffeners is discussed. The feasibility using existing design codes to predict the load-carrying capacities of the stiffened composite columns is also dealt with in this paper.

Seismic behavior of composite connections — flexural capacity analysis

Based on the experimental results of connections composed of concrete-filled square steel tubular columns and steel–concrete composite beams with interior diaphragms or anchored studs, the flexural capacity of connections is studied theoretically in the present paper. Analytical models are proposed, with consideration of the effects of axial load, concrete slab, middle interior diaphragm, beam and column width condition, and punching shear failure mode. Formulae in different conditions are established based on these models. The predictions and the test results are compared and they are in good agreement.

Analytical behavior of frames with steel beams to concrete-filled steel tubular column

This paper reports the mechanism of composite frames with steel beams connected to concrete-filled square hollow section (SHS) columns. Detailed analysis was carried out on longitudinal stress in steel beams, axial stress distribution in concrete, and concrete stress along the column height and at the connection panel. Parametric studies were conducted to investigate the influence of axial load level, beam-to-column linear stiffness ratio on the structural behavior of composite frames. Simplified hysteretic lateral load ( P ) versus lateral displacement ( Δ ) models are proposed for such composite frames.

Concrete-Filled Square and Rectangular FRP Tubes under Axial Compression

This paper presents results of an experimental study on the behavior of square and rectangular concrete-filled fiber reinforced polymer (FRP) tubes (CFFTs) under concentric compression. FRP tubes were designed as column confinement reinforcement and were manufactured using unidirectional carbon fiber sheets with fibers oriented in the hoop direction. The effects of the thickness and corner radius of the tube, sectional aspect ratio, and concrete strength on the axial behavior of CFFTs were investigated experimentally. Test results indicate that FRP confinement leads to substantial improvement in the ductility of both square and rectangular columns. Confinement provided by the FRP tube may also improve the axial load-carrying capacity of the square and rectangular columns if the confinement effectiveness of the FRP tube is sufficiently high. The results also indicate that the confinement effectiveness of FRP tubes is higher in square columns than in rectangular columns, and in both sections the effectiveness of confinement increases with the corner radius. Furthermore, for a given confinement level, improvement observed on the axial behavior of concrete due to confinement decreases with increasing concrete strength.