scholarly journals Research on Compression Behavior of Square Thin-Walled CFST Columns with Steel-Bar Stiffeners

2018 ◽  
Vol 8 (9) ◽  
pp. 1602 ◽  
Author(s):  
Zhao Yang ◽  
Chengxiang Xu
Keyword(s):  
Bearing Capacity ◽  
Local Buckling ◽  
Steel Tube ◽  
Steel Tubes ◽  
Compression Behavior ◽  
Steel Bar ◽  
Steel Bars ◽  
Thin Walled ◽  
Structural Measure ◽  
Cfst Columns

Local buckling in steel tubes was observed to be capable of reducing the ultimate loads of thin-walled concrete-filled steel-tube (CFST) columns under axial compression. To strengthen the steel tubes, steel bars were proposed in this paper to be used as stiffeners fixed onto the tubes. Static-loading tests were conducted to study the compression behavior of square thin-walled CFST columns with steel bar stiffeners placed inside or outside the tube. The effect and feasibility of steel bar stiffeners were studied through the analysis of failure mode, load–displacement relationship, ultimate load, ductility, and local buckling. Different setting methods of steel bars were compared as well. The results showed that steel-bar stiffeners proposed in this paper can be effective in delaying local buckling as well as increasing the bearing capacity of the columns, but will decrease the ductility of the columns. In order to obtain a higher bearing capacity of columns, steel bars with low stiffness should be placed inside and steel bars with high stiffness should be placed outside of the steel tubes. The study is helpful in providing reference to the popularization and application of this new structural measure to avoid or delay the local buckling of thin-walled CFST columns.

scholarly journals Buckling Analysis and Section Optimum for Square Thin-Wall CFST Columns Sealed by Self-Tapping Screws

2019 ◽  
Vol 2019 ◽  
pp. 1-14
Author(s):  
He Zhang ◽  
Kai Wu ◽  
Chao Xu ◽  
Lijian Ren ◽  
Feng Chen
Keyword(s):  
Bearing Capacity ◽  
Failure Modes ◽  
Steel Plate ◽  
Local Buckling ◽  
Steel Tube ◽  
Thin Wall ◽  
Type Section ◽  
Plate Buckling ◽  
Thin Walled ◽  
Cfst Columns

Two columns of thin-walled concrete-filled steel tubes (CFSTs), in which tube seams are connected by self-tapping screws, are axial compression tested and FEM simulated; the influence of local buckling on the column compression bearing capacity is discussed. Failure modes of square thin-wall CFST columns are, first, steel tube plate buckling and then the collapse of steel and concrete in some corner edge areas. Interaction between concrete and steel makes the column continue to withstand higher forces after buckling appears. A large deflection analysis for tube elastic buckling reflects that equivalent uniform stress of the steel plate in the buckling area can reach yield stress and that steel can supply enough designing stress. Aiming at failure modes of square thin-walled CFST columns, a B-type section is proposed as an improvement scheme. Comparing the analysis results, the B-type section can address both the problems of corner collapse and steel plate buckling. This new type section can better make full use of the stress of the concrete material and the steel material; this type section can also increase the compression bearing capacity of the column.

scholarly journals Axial Loading Behaviour of Self-Compacting Concrete-Filled Thin-Walled Steel Tubular Stub Columns

2021 ◽  
Vol 2021 ◽  
pp. 1-7
Author(s):  
Yunyang Wang ◽  
Lei Xiao ◽  
Chu Jiang ◽  
Yandong Jia ◽  
Guang Yang ◽  
...  
Keyword(s):  
Failure Modes ◽  
Ultimate Load ◽  
Local Buckling ◽  
Axial Loading ◽  
Steel Tube ◽  
Self Compacting Concrete ◽  
Steel Tubes ◽  
Thin Walled ◽  
Stub Columns ◽  
Versus Strain

This paper presents an experimental investigation on the mechanical behaviour of self-compacting concrete-filled thin-walled steel tubular (SCCFTST) stub columns loaded in axial compression to failure. Four specimens were tested to study the effect of diameter to wall thickness (D/t) ratios on the ultimate load, failure modes, and ductility of the columns. Confinement of the steel tube to concrete was also addressed. The failure modes, load versus displacement curves, and load versus strain curves were examined in detail. The experimental results showed that the ultimate state is reached when severe local buckling and rupture occurred on the steel tubes, and the concrete near the rupture has been crushed. The columns with larger D/t ratios appeared more local buckling, and its location is more close to the end of the columns. The SCCFTST stub columns with smaller D/t ratios show higher ultimate load and better ductility, and the steel tubes can exert higher confinement to the concrete.

scholarly journals Degradation of Axial Ultimate Load-Bearing Capacity of Circular Thin-Walled Concrete-Filled Steel Tubular Stub Columns after Corrosion

Materials ◽  
2020 ◽  
Vol 13 (3) ◽  
pp. 795 ◽  
Author(s):  
Fengjie Zhang ◽  
Junwu Xia ◽  
Guo Li ◽  
Zhen Guo ◽  
Hongfei Chang ◽  
...  
Keyword(s):  
Bearing Capacity ◽  
Ultimate Load ◽  
Steel Tube ◽  
Parameter Analysis ◽  
Loading Test ◽  
Steel Tubes ◽  
Load Bearing Capacity ◽  
Load Bearing ◽  
Thin Walled ◽  
Stub Columns

This work aimed to investigate the effects of steel tube corrosion on the axial ultimate load-bearing capacity (AULC) of circular thin-walled concrete-filled steel tubular (CFST) members. Circular thin-walled CFST stub column specimens were made of steel tubes with various wall-thicknesses. These CFST column specimens were subjected to an accelerated corrosion test, where the steel tubes were corroded to different degrees of corrosion. Then, these CFST specimens with corroded steel tubes experienced an axial static loading test. Results show that the failure patterns of circular thin-walled CFST stub columns with corroded steel tubes are different from those of the counterpart CFST columns with ordinary wall-thickness steel tubes, which is a typical failure mode of shear bulging with slight local outward buckling. The ultimate strength and plastic deformation capacity of the CFST specimens decreased with the increasing degree of steel corrosion. The failure modes of the specimens still belonged to ductile failure because of the confinement of outer steel tube. The degree of steel tube corrosion, diameter-to-thickness ratio, and confinement coefficient had substantial influences on the AULC and the ultimate compressive strength of circular thin-walled CFST stub columns. A simple AULC prediction model for corroded circular thin-walled CFST stub columns was presented through the regression of the experimental data and parameter analysis.

The Experimental Study on Concrete-Filled Thin-Walled Square Steel Box Short Columns Fixed with Composite Steel Bar

2011 ◽  
Vol 94-96 ◽  
pp. 1590-1595
Author(s):  
Hai Chao Wang ◽  
Xi Quan Xu ◽  
Li Jun Zhou
Keyword(s):  
Bearing Capacity ◽  
Concrete Strength ◽  
Testing Machine ◽  
Short Columns ◽  
Steel Bar ◽  
Bonding Effect ◽  
Steel Bars ◽  
Thin Walled ◽  
Transverse Steel ◽  
Composite Steel

The method of construction about the concrete-filled thin-walled square steel box short columns is studied in this paper. Composite steel is designed inside of the concrete-filled thin-walled square steel box short columns. The use of the transverse steel bars’ constraining effect on the concrete and bonding effect on the walls enhances the local stability and bearing capacity of the wall. According to the concrete strength C30/C35/C40 and the thickness of the steel 1.25mm/1.75mm/2.5mm,42 short column specimens are made and the size of all specimens is 200mm×200mm×690mm.The static bearing capacity test is done by the 500-ton electro-hydraulic serve testing machine. The whole curve is made .The composite steel and the thin-walled steel’s strain is tested. The results show that this method of construction has a certain effect on constrainting concrete and bonding effect on the walls, significantly improving their mechanical properties, increasing the carrying capacity and ductility, and it is easy to be accomplished.

Behavior of CFRP-confined reactive powder concrete-filled steel tubes under axial compression

2020 ◽  
pp. 136943322097478
Author(s):  
Song Li ◽  
Chu-Jie Jiao
Keyword(s):  
Bearing Capacity ◽  
Axial Compression ◽  
Local Buckling ◽  
Steel Tube ◽  
Experimental Results ◽  
Reactive Powder Concrete ◽  
Test Results ◽  
Steel Tubes ◽  
Reactive Powder ◽  
Concrete Filled Steel Tubes

Reactive powder concrete-filled steel tubes (RPCFSTs) have become an important research target in recent years. In engineering applications, RPCFSTs can provide superior vertical components for high-rise and tower buildings, thereby enabling developers to provide more floor space. However, this type of composite structure is prone to inelastic outward local buckling. The use of carbon fiber reinforced polymer (CFRP) wrapping to suppress such local buckling has shown great potential in limited test results. This paper presents experimental results concerning the axial compression of CFRP-confined reactive powder concrete-filled circular steel tubes (CF-RPCFSTs). We included 18 specimens in our experimental investigation, varying the number of CFRP layers, steel tube thickness, and RPC strength. According to our test results, CF-RPCFSTs exhibit compression shear failure and drum-shaped failure. The CFRP wrap can effectively enhance bearing capacity and postpone local buckling of the steel tube. In addition, three-layer CFRP-confined RPC-filled thin-wall steel tubes are suitable for engineering. We also propose a model to calculate the bearing capacity of CF-RPCFSTs. Compared to the existing model of CFRP-confined concrete-filled steel tubes, the results obtained using the proposed model are in good agreement with our experimental results.

scholarly journals Derivation of the unified equation of axial compression of CFST columns

2020 ◽  
Vol 143 ◽  
pp. 01004
Author(s):  
Ruoyang Zhou ◽  
Xiaoxiong Zha
Keyword(s):  
Bearing Capacity ◽  
Axial Compression ◽  
Limit Equilibrium ◽  
Concrete Columns ◽  
Steel Tube ◽  
Steel Reinforcement ◽  
Steel Plates ◽  
Steel Tubes ◽  
High Rise ◽  
Cfst Columns

The steel tube concrete columns with steel reinforcement cages, steel plates and steel tubes has been used in super high-rise buildings, which are called concrete-filled steel tubular (CFST) columns with internal stiffeners. Based on the theory of limit equilibrium, the unified equation for the axial bearing capacity of the CFST columns with internal stiffeners is obtained. The derived equation in this study can provide reference for the future engineering applications.

scholarly journals Experimental Study on Axial Compressive Behavior of Gangue Aggregate Concrete Filled FRP and Thin-Walled Steel Double Tubular Columns

Coatings ◽  
2021 ◽  
Vol 11 (11) ◽  
pp. 1404
Author(s):  
Jian Wang ◽  
Junwu Xia ◽  
Hongfei Chang ◽  
Youmin Han ◽  
Linli Yu ◽  
...  
Keyword(s):  
Stress State ◽  
Bearing Capacity ◽  
Axial Stress ◽  
Local Buckling ◽  
Steel Tube ◽  
Outer Diameter ◽  
Aggregate Concrete ◽  
Tubular Columns ◽  
Inner Diameter ◽  
Thin Walled

In the present paper, the monotonic axial compression test of gangue aggregate concrete filled Fiber reinforced polymer (FRP) and thin-walled steel double tubular columns (DTCC) was carried out, and the gangue aggregate concrete filled FRP tubular columns (CFFT) were designed as a comparison. The main experimental factors were the confinement level of the FRP jacket, the relative diameter ratio (the ratio of the outer diameter of the steel tube to the inner diameter of the FRP jacket), and the different strengths of gangue aggregate concrete. The test results show that the bearing capacity and ductility of gangue aggregate concrete in CFFT were significantly improved. As the local buckling of thin-walled steel tube was effectively inhibited, the load bearing capacity of DTCC was further improved compared with CFFT, but the change of dilation behavior and ductility was insignificant. By analyzing the bi-directional stress state of the steel tube, the confinement level of the external FRP jacket was the most sensitive factor affecting the hoop stress of the steel tube, and the axial stress was obviously weakened under the bi-directional stress state. In addition, with the increase of steel tube diameter, the confinement effect of steel tube in DTCC became more obvious.

ELASTIC BUCKLING OF THIN-WALLED CIRCULAR TUBES CONTAINING AN ELASTIC INFILL

2006 ◽  
Vol 06 (04) ◽  
pp. 457-474 ◽  
Author(s):  
M. A. BRADFORD ◽  
A. ROUFEGARINEJAD ◽  
Z. VRCELJ
Keyword(s):  
Axial Compression ◽  
A Priori ◽  
Local Buckling ◽  
Steel Tube ◽  
Transcendental Equation ◽  
Buckling Mode ◽  
Buckling Stress ◽  
Elastic Tubes ◽  
Thin Walled ◽  
Energy Formulation

Circular thin-walled elastic tubes under concentric axial loading usually fail by shell buckling, and in practical design procedures the buckling load can be determined by modifying the local buckling stress to account empirically for the imperfection sensitive response that is typical in Donnell shell theory. While the local buckling stress of a hollow thin-walled tube under concentric axial compression has a solution in closed form, that of a thin-walled circular tube with an elastic infill, which restrains the local buckling mode, has received far less attention. This paper addresses the local buckling of a tubular member subjected to axial compression, and formulates an energy-based technique for determining the local buckling stress as a function of the stiffness of the elastic infill by recourse to a transcendental equation. This simple energy formulation, with one degree of buckling freedom, shows that the elastic local buckling stress increases from 1 to [Formula: see text] times that of a hollow tube as the stiffness of the elastic infill increases from zero to infinity; the latter case being typical of that of a concrete-filled steel tube. The energy formulation is then recast into a multi-degree of freedom matrix stiffness format, in which the function for the buckling mode is a Fourier representation satisfying, a priori, the necessary kinematic condition that the buckling deformation vanishes at the point where it enters the elastic medium. The solution is shown to converge rapidly, and demonstrates that the simple transcendental formulation provides a sufficiently accurate representation of the buckling problem.

The Study on Static Force Behavior of Concrete Filled Steel Tube Lattice Wind Generator Tower Joints

2013 ◽  
Vol 671-674 ◽  
pp. 833-837
Author(s):  
Yang Wen ◽  
Fei Zhou
Keyword(s):  
Tube Wall ◽  
Local Buckling ◽  
Steel Tube ◽  
Wall Region ◽  
Steel Tubes ◽  
Concrete Filled Steel Tube ◽  
Wind Generator ◽  
Nonlinear Static ◽  
Angle Steel ◽  
Section Form

In order to discuss the failure mechanism of concrete filled steel tube lattice wind generator tower joints. Based on the parameters of web member section form, and using nonlinear static numerical simulation, this dissertation research on the stressed complex joints. The results of the study show that the abdominal rod for circular steel tubes joint (JD1) is instability failure which is led to the local buckling of compressive bar; the abdominal rod for single angle steel (JD2) or double angle steel (JD3) joint is instability failure because of the local buckling of the joint board. Under the web members and joint boards all fitting their own capacity requirements, JD1 is very easy to make draw bar broken on both sides of the pillar tube wall region, JD2 and JD3 are apt to damage on the weak positions of joint board ends and pillar tube wall joint. In the three forms of web member joints, the best ultimate bearing capacity is JD1 , JD3 is the second and JD2 is minimum.

scholarly journals Axial Behaviour of Slender RC Circular Columns Strengthened with Circular CFST Jackets

2018 ◽  
Vol 2018 ◽  
pp. 1-11 ◽  
Author(s):  
Yiyan Lu ◽  
Tao Zhu ◽  
Shan Li ◽  
Weijie Li ◽  
Na Li
Keyword(s):  
Bearing Capacity ◽  
Ductile Failure ◽  
Steel Tube ◽  
Experimental Results ◽  
Strengthening Effect ◽  
Load Bearing Capacity ◽  
Rc Columns ◽  
Load Bearing ◽  
Cfst Columns ◽  
Material Utilization

This paper investigates the axial behavior of slender reinforced concrete (RC) columns strengthened with concrete filled steel tube (CFST) jacketing technique. It is realized by pouring self-compacting concrete (SCC) into the gap between inner original slender RC columns and outer steel tubes. Nine specimens were prepared and tested to failure under axial compression: a control specimen without strengthening and eight specimens with heights ranging between 1240 and 2140 mm strengthened with CFST jacketing. Experimental variables included four different length-to-diameter (L/D) ratios, three different diameter-to-thickness (D/t) ratios, and three different SCC strengths. The experimental results showed that the outer steel tube provided confinement to the SCC and original slender RC columns and thus effectively improved the behavior of slender RC columns. The failure mode of slender RC columns was changed from brittle failure (concrete peel-off) into ductile failure (global bending) after strengthening. And, the load-bearing capacity, material utilization, and ductility of slender RC columns were significantly enhanced. The strengthening effect of CFST jacketing decreased with the increase of L/D ratio and D/t ratio but showed little variation with higher SCC strength. An existing expression of load-bearing capacity for traditional CFST columns was extended to propose a formula for the load-bearing capacity of CFST jacketed columns, and the predictions showed good agreement with the experimental results.

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