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.

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.

Experiment Study on Interfacial Normal Bond Strength of Concrete Filled Steel Tube

2012 ◽  
Vol 594-597 ◽  
pp. 947-954 ◽  
Author(s):  
Zhen Yu Liu
Keyword(s):  
Bond Strength ◽  
Temperature Change ◽  
Concrete Strength ◽  
Steel Tube ◽  
Test Method ◽  
Bending Test ◽  
Concrete Filled Steel Tube ◽  
Normal Bond ◽  
Core Concrete ◽  
Test Result

To study the debonding of concrete filled steel tube (CFST), pulling and bending methods were used to test the normal bond strength. Based on the test result, debonding due to temperature change and shrinkage of core concrete in CFST was analyzed. The test and analysis result shows that the bending method is a better test method; the concrete strength has little influence on bond strength while the surface condition of steel has much influence on it. The bond strength of steel which is rust is greater than that of the steel with smooth surface. According to the analysis on the bending test result, the normal bond strength of 0.86MPa was got and the debonding of CFST arch was analyzed, the analysis result shows that debonding will easily happen under the action of temperature change and shrinkage of core concrete. The test methods and results can provide a reference for engineering applications.

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.

Combined Application of Three Nondestructive Testing Methods in Simulation Test of a Large Concrete-Filled Steel Tube

2013 ◽  
Vol 738 ◽  
pp. 121-127
Author(s):  
Ming Ru Zhou ◽  
Zhong Yu Guo ◽  
Qiong Fei Shen ◽  
Zheng Bo Li
Keyword(s):  
Nondestructive Testing ◽  
Strain Analysis ◽  
Steel Tube ◽  
Testing Methods ◽  
Simulation Test ◽  
Bonding Quality ◽  
Concrete Filled Steel Tube ◽  
Combined Application ◽  
Key Factor ◽  
Nondestructive Testing Methods

Bonding quality is the key factor that affects the safety of concrete-filled steel tube (CFST) structure, so it is a very important research that how to judge the bonding quality. This paper expounded the theory of three methods used in nondestructive testing of CFST, and introduced the combined application of the methods of artificial tapping, ultrasonic testing, and strain analysis in a large simulation test.

Effect of Expansive Agent on Concrete Filled Steel Tube

2018 ◽  
Vol 1145 ◽  
pp. 95-99
Author(s):  
Hua Li ◽  
Jia Ping Liu ◽  
Qian Tian ◽  
Fei Guo
Keyword(s):  
Temperature Rise ◽  
Autogenous Shrinkage ◽  
Steel Tube ◽  
Displacement Sensor ◽  
Scale Model ◽  
Concrete Filled Steel Tube ◽  
Cooling Stage ◽  
Expansive Agent ◽  
Initial Setting ◽  
Project Site

The shrinkage of concrete is one of the main causes of cavity in concrete filled steel tube (CFST). In this paper, the effect of a kind of lab-made expansive agent on the deformation of CFST is studied. The laser displacement sensor combined with the round straight steel tube mould was adopted to test the deformation of concrete from the initial setting to 1 day after pouring, and the mechanical micrometer method was used to test deformation after 1 day in the laboratory. The full-scale model test was carried out to monitor the effect of expansive agent in CFST at the project site. The results show that, the addition of expansive agent produced significant expansion in the first 3 days, with the expansion basically compensating the autogenous shrinkage of the concrete; influenced by thermal deformation, the constraint action of steel tube to the core concrete in temperature rise stage was far greater than that in cooling stage. Compared with expansion produced in temperature rise stage, it is more important to produce expansion in cooling stage to solve the cavity problem of CFST.

scholarly journals Axial Compression Performance and Ultrasonic Testing of Multicavity Concrete-Filled Steel Tube Shear Wall under Axial Load

2020 ◽  
Vol 2020 ◽  
pp. 1-19
Author(s):  
Hongbo Li ◽  
Pengfei Yan ◽  
Hao Sun ◽  
Jianguang Yin
Keyword(s):  
Finite Element ◽  
Axial Compression ◽  
Ultrasonic Testing ◽  
Axial Load ◽  
Limit Equilibrium ◽  
Concrete Strength ◽  
Shear Wall ◽  
Steel Tube ◽  
Concrete Filled Steel Tube ◽  
Core Concrete

In this study, the mechanical performance of multicavity concrete-filled steel tube (CFST) shear wall under axial compressive loading is investigated through experimental, numerical, and theoretical methodologies. Further, ultrasonic testing is used to assess the accumulated damage in the core concrete. Two specimens are designed for axial compression test to study the effect of concrete strength and steel ratio on the mechanical behavior of multicavity CFST shear wall. Furthermore, a three-dimensional (3D) finite element model is established for parametric studies to probe into compound effect between multicavity steel tube and core concrete. Based on finite element simulation and limit equilibrium theory, a practical formula is proposed for calculating the axial compressive bearing capacity of the multicavity CFST shear wall, and the corresponding calculation results are found to be in good agreement with the experimental results. This indicates that the proposed formula can serve as a useful reference for engineering applications. In addition, the ultrasonic testing results revealed that the damage process of core concrete under axial load can be divided into three stages: extension of initial cracks (elastic stage), compaction due to hooping effect (elastic-plastic stage), and overall failure of the concrete (failure stage).

Influence of Hoop Coefficient on Dynamic Response of Railway Bridge Protective Frame under Impact Load

2011 ◽  
Vol 291-294 ◽  
pp. 1321-1326
Author(s):  
Ao Tian Ju ◽  
Shu Ying Qu ◽  
Xing Min Hou ◽  
Jin Tian Wang
Keyword(s):  
Dynamic Response ◽  
Wall Thickness ◽  
Tube Wall ◽  
Impact Load ◽  
Steel Tube ◽  
Railway Bridge ◽  
Concrete Filled Steel Tube ◽  
Tube Wall Thickness ◽  
Average Impact ◽  
Tube Structure

The paper analyzes that hoop coefficients of the concrete-filled steel tube influence on dynamic response of the railway bridge height limit protective frame under impact load by using ANSYS/LS-DYNA. Change hoop coefficient of the concrete-filled steel tube structure by changing steel tube wall thickness. The result shows that with increase of steel tube wall thickness, the average impact force of protective frame will increase and the displacement and deformation will reduce, and protective frame can resist greater impact load. It will provide the reference for design of railway bridge height limit protective frame.

Influence of concrete mix proportions on axial performance of concrete-filled steel tubes made with self-compacting concrete

2019 ◽  
Vol 23 (5) ◽  
pp. 835-846 ◽  
Author(s):  
Y Ouyang ◽  
JJ Zeng ◽  
LG Li ◽  
AKH Kwan
Keyword(s):  
Steel Tube ◽  
The Self ◽  
Use Of Self ◽  
Self Compacting Concrete ◽  
Steel Tubes ◽  
Concrete Filled Steel Tube ◽  
Concrete Mix ◽  
Key Factor ◽  
Air Void ◽  
Concrete Filled Steel Tubes

Self-compacting concrete is quite commonly used in concrete-filled steel tube structures, but the compaction level of the self-compacting concrete, that is, the percentage of volume occupied by materials other than air void, within the steel tube is seldom investigated. The authors are of the view that the concrete mix proportions of the self-compacting concrete may have significant effects on the compaction level of the self-compacting concrete, which will be quantified by the ‘compaction index’ proposed in this study and thus the performance of the concrete-filled steel tube. Moreover, the mix proportions would also influence the performance of the concrete-filled steel tube by affecting the aggregate–aggregate and aggregate–paste interactions of the concrete, albeit this important issue is rarely addressed in previous studies either. Herein, a pilot study is conducted to investigate the influences of the self-compacting concrete mix proportions on the axial performance of concrete-filled steel tube. Four groups of concrete-filled steel tube specimens made with different self-compacting concrete were tested, and the investigated concrete mix parameters included the paste volume, fine to coarse aggregate ratio, and 9.5–19.0 mm aggregate ratio. It was found that the compaction index of the self-compacting concrete is a key factor enabling the successful use of self-compacting concrete in concrete-filled steel tube. Moreover, the paste volume and aggregate proportions of the concrete mix have certain effects on the post-peak behaviour and ductility of concrete-filled steel tube.

Push-Out Test on Bond Property of Micro-Expansive Concrete-Filled Steel Tube Columns

2010 ◽  
Vol 163-167 ◽  
pp. 610-614 ◽  
Author(s):  
Kai Cheng Xu ◽  
Meng Cheng Chen ◽  
Fang Yuan
Keyword(s):  
Bond Strength ◽  
Composite Structures ◽  
Steel Tube ◽  
Conventional Concrete ◽  
Concrete Filled Steel Tube ◽  
Expansive Agent ◽  
Expansive Concrete ◽  
Expansion Behavior ◽  
Bond Property ◽  
Cfst Columns

The shrinkage/expansion behavior and bond carrying capacities of 4 short, micro-expansive concrete-filled steel tube (MCFST) and 3 short, conventional concrete-filled steel tube (CFST) columns were experimentally investigated. The results indicate that pre-stress is produced in the core concrete under the confined by the steel tube. Both expansive agent and water cement ratio have important influence on expansive behaviors of MCFST. The current work also indicates that the MCFST columns have higher bond strength than conventional CFST columns and this recommends a new method to improve the bond strength of composite structures.

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