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.

Experiment Study on Cyclic Behavior of Concrete Filled Steel Tube (CFST) Column-Reinforced Concrete (RC) Beam Connections

2009 ◽  
Vol 417-418 ◽  
pp. 833-836 ◽  
Author(s):  
Qing Xiang Wang ◽  
Shi Run Liu
Keyword(s):  
Reinforced Concrete ◽  
Tube Wall ◽  
Plastic Hinge ◽  
Steel Tube ◽  
Reinforced Concrete Beams ◽  
Cyclic Behavior ◽  
Concrete Core ◽  
Concrete Filled Steel Tube ◽  
Steel Bars ◽  
Moment Resisting

The test results of six connections under cyclic loading are presented in the paper. Each test specimen was properly designed to model the interior joint of a moment resisting frame, and was identically comprised of three parts that including the circular concrete filled steel tube columns, the reinforced concrete beams, and the short fabricated connection stubs. Energy dissipation was designed to occur in the beams during a severe earthquake. Steel bars which were embedded into concrete core and welded to the connection stubs, were used to transfer the force distributed by the reinforcing bars of concrete beam to the concrete core. The results indicated that the embedded steel bars were very efficient in eliminating the stress concentration on the tube wall and there was no visible deformation occurred on the tube wall until the collapse of the specimen. Furthermore, the connection of each specimen had enough capacity and thus the plastic hinge appeared in the beams. As results, the ductility of this new type structure directly depended on the RC beams.

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.

Axial impact behaviors of stub concrete-filled square steel tubes

2019 ◽  
Vol 22 (11) ◽  
pp. 2490-2503 ◽  
Author(s):  
YT Zhang ◽  
B Shan ◽  
Y Xiao
Keyword(s):  
Finite Element ◽  
Failure Modes ◽  
Steel Tube ◽  
Experimental Results ◽  
Parameter Analysis ◽  
Steel Tubes ◽  
Simple Method ◽  
Concrete Filled Steel Tube ◽  
Drop Weight ◽  
The Impact

Existing research on the widely used concrete-filled steel tubes is mainly focused on static or cyclic loading, and the studies on effects of high strain rate are relatively rare. In this article, seven stub concrete-filled steel tubular columns with square section were tested under both static and impact loads, using a large-capacity drop-weight testing machine. The research parameters were variable height of the drop-weight and different load types. The experimental results show that the failure modes of the concrete-filled steel tube columns from the impact tests are similar with those under static load, characterized by the local buckling of the steel tube. The time history curves of impact force and steel strain were investigated. The results indicate that with increasing impact energy, the concrete-filled steel tube stub columns had a stronger impact-resistant behavior. The dynamic analysis software LS-DYNA was employed to simulate the impact behaviors of the concrete-filled steel tube specimens, and the finite element results were reasonable compared with the test results. The parameter analysis on the impact behavior of concrete-filled steel tube columns was performed using the finite element model as well. A simple method was proposed to calculate the impact strength of square concrete-filled steel tube columns and compared favorably with experimental results.

scholarly journals Experimental Studies on the Effect of Properties and Micro-Structure on the Creep of Concrete-Filled Steel Tubes

Materials ◽  
2019 ◽  
Vol 12 (7) ◽  
pp. 1046 ◽  
Author(s):  
Rongling Zhang ◽  
Lina Ma ◽  
Qicai Wang ◽  
Jia Li ◽  
Yu Wang ◽  
...  
Keyword(s):  
Pore Structure ◽  
Steel Tube ◽  
Creep Tests ◽  
Steel Tubes ◽  
Concrete Filled Steel Tube ◽  
Steel Ratio ◽  
Air Content ◽  
Lateral Restraint ◽  
Concrete Filled Steel Tubes ◽  
Core Concrete

To study different lateral restraints, different constituents of expansion agents, the influence of different steel ratios, and concrete creep properties, we carried out experiments with lateral restraint and without lateral restraint conditions separately on 12 specimens with the expansion agent content accounting for 4%, 8%, and 12% respectively. In addition, the creep tests were performed on specimens with different steel ratios of 0.0%, 3.8%, 6.6%, and 9.2%. The test results show that the lateral restraint improves the strength of the system (concrete-filled steel tubes) which resists further load after the concrete ultimate strength is surpassed and reduces the creep. The creep degree of the concrete-filled steel tube with lateral restraint is about 0.09–0.30 times smaller than that of the tube without lateral restraints. The creep degree of the concrete-filled steel tube increases as the steel ratio decreases. Creep tests with different amounts of expansion agent indicate that the creep degree of the concrete structure increases as expansion agent content decreases. To study the internal mechanism of the creep of concrete-filled steel tubes with different lateral restraints and different expansion agent concentrations, a microscopic pore structure test on the steel core concrete was conducted using the RapidAir457 pore structure instrument. Microscopic studies show that the air content and the length of the bubble chord of the laterally restrained core concrete are lower than those without lateral restraint core concrete. The amount of air content and the length of the bubble chord of core concrete specimens increase as the expansion agent content in the core concrete specimens decreases from 12% to 4%. Under the same external loading conditions, as steel ratio increases, the lateral restraint causes a further reduction of creep. The results of this study suggest that the creep of concrete can be reduced by selecting appropriate lateral restraint conditions and an optimal amount of expansion agent in the mix design of concrete for concrete-filled steel tubes.

Analysis on the Status of Concrete Filled Double Skin Steel Tubes Mechanical Properties

2014 ◽  
Vol 488-489 ◽  
pp. 374-376
Author(s):  
Bing Wang ◽  
Lu Ma ◽  
Xiao Liu
Keyword(s):  
Mechanical Properties ◽  
Research Work ◽  
Steel Tube ◽  
Steel Tubes ◽  
Concrete Filled Steel Tube ◽  
Research Results ◽  
Foreign Literature ◽  
The Status ◽  
Double Skin

Concrete filled double skin steel tubes which is developed on the basis of concrete filled steel tube, it is a new member. Combination of Chinese and foreign literature, this paper comprehensively discusses the research results about concrete filled double skin steel tubes member, then put forward the further research work, for concrete filled double skin steel tubes structure in deeply study to play a guiding role.

Study on Stress-Strain Relationship of FRP-Confined Concrete Filled Steel Tubes

2010 ◽  
Vol 163-167 ◽  
pp. 3826-3829
Author(s):  
Feng Yu ◽  
Ping Wu
Keyword(s):  
Main Parameter ◽  
Steel Tube ◽  
Confined Concrete ◽  
Stress Strain ◽  
Steel Tubes ◽  
Concrete Filled Steel Tube ◽  
Strain Relationship ◽  
Relationship Of ◽  
Concrete Filled Steel Tubes ◽  
Strain Model

FRP-confined concrete filled steel tube may fully use the character of FRP-confined concrete and concrete filled steel tube. Based on the analysis of existing experimental data, the formula of ultimate bearing capacity of FRP-confined concrete filled steel tube is proposed. The mechanical behavior of FRP-confined concrete filled steel tube is mainly related to the equivalent confinement effect coefficient before the rupture of FRP. Based on the static equilibrium condition, the equivalent conversion section is adopted; taking as main parameter, the simplified stress-strain model of FRP-confined concrete filled steel tube is established. The predictions of the model agree well with test data.

Improvement of Volume Stability in Core Concrete of Concrete-Filled Steel Tube

2011 ◽  
Vol 52-54 ◽  
pp. 1097-1106
Author(s):  
De Bin Yang ◽  
Shui Xing Zhou ◽  
Ming Chen ◽  
Wei Wang ◽  
Xiao Yi Zhang
Keyword(s):  
Tube Wall ◽  
Steel Tube ◽  
Concrete Filled Steel Tube ◽  
Volume Stability ◽  
Expansive Agent ◽  
Shrinkage Effect ◽  
Key Factor ◽  
Curing Condition ◽  
Water Saturated ◽  
Core Concrete

Due to the concrete self-shrinkage, frequent load application and temperature fluctuation, and so on，the gap formed between the inner tube wall and the core concrete surfaces would decrease the performance of concrete-filled steel tube (CFST). To prevent this cavity problem, various types of expansive agents and aggregates were used in this study to improve the volume stability of core concrete. Comparative experiments with mortars and concrete were carried out respectively under standard curing condition and under enclosed curing condition which simulated the environment in steel tube. The results could be summarized as follows: ● Two types of expansive agents, ZY type expansive agent mainly containing sulfates and aluminates and M type expansive agent mainly containing magnesium oxide, presented different expansive behaviors with curing ages in mortar and concrete. Two types of expansive agents combined with each other could produce complementary and superimposition effects to improve continuously the volume stability of mortar and concrete. ● Sufficient water supply is the key factor for the formation and maintenance of expansion. The volume change caused by the self-shrinkage effect of core concrete could not be effectively off-set with whether two types expansive agents or their compounds under enclosed environment in which water was scarce and could not be supplied from outside. ● When some water-saturated ceramsite were used to partially replace aggregates in core concrete,the volume expansion performance of core concrete improved dramatically with the water storage and supply effects of water-saturated ceramsite.

Structural Performance of High Strength Concrete Filled Steel Tube with the Width-to-Thickness Ratio

2013 ◽  
Vol 284-287 ◽  
pp. 1390-1395
Author(s):  
Geon Ho Hong ◽  
Won Ki Kim ◽  
In Rak Choi ◽  
Kyung Soo Chung
Keyword(s):  
High Strength Steel ◽  
Local Buckling ◽  
Tall Buildings ◽  
High Strength ◽  
Steel Tube ◽  
Thickness Ratio ◽  
Maximum Strength ◽  
Structural Performance ◽  
Deformation Capacity ◽  
Concrete Filled Steel Tube

Concrete filled steel tube has been consistently used in tall buildings as it represents excellent structural performance and economical efficiency compared with other structural systems. The use of high strength steel in concrete filled steel tube can reduce the column size and increase the effective space in the buildings. But, the limit of width-to-thickness ratio to prevent local buckling is an obstacle to applying the high strength steel as it considerably decrease following to the strength increase. This paper addresses the effect of steel plate slenderness limit on the compression behavior in 800 MPa Grade steel. Four short column specimens were tested under axial compression. Main test variables were width-to-thickness ratio and shape of section. Test results were analyzed in the viewpoint of local buckling strength, yield strength, maximum strength and plastic deformation capacity of specimens. The experimental results showed that all specimens exceeded the maximum strength of calculated value by design code and represented similar deformation capacity regardless of width-to-thickness ratio. So, the limit of width-to-thickness ratio in high strength steel could be amended less strict.

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