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.

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.

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.

Definition of rheological characteristics of self-compacting concretes in Russian and foreign regulatory documents

2019 ◽  
pp. 39-45
Keyword(s):  
Water Content ◽  
The Self ◽  
National Standard ◽  
Rheological Characteristics ◽  
Use Of Self ◽  
Self Compacting Concrete ◽  
Regulatory Documents ◽  
Regulatory Frameworks ◽  
Concrete Mix ◽  
Definition Of

The article is devoted to the comparison of acting domestic and foreign regulatory frameworks for assessing properties of the self-compacting concrete. Advantages of the self-compacting concrete mix such as improved flowability and high density at low water content due to what this material has been widely used abroad are presented. In addition, the main rheological characteristics of self-compacting concretes concerning the mobility of the mix, viscosity and segregation, as well as methods for their evaluation with the use of a cone flow diameter, V-shaped funnel, L-shaped box, blocking J-ring are considered. Visual indexes of stability and possibilities of their use are shown. It is noted that when producing concretes it is necessary to provide for possible shrinkage by compensating it due to the use of self-stressing concretes, self-stressing cements and expanding additives, especially when using self-compacting concretes, which exclude forced compaction (vibration). The article reveals the need to develop the national standard and its harmonization with foreign analogs and modification of the Sets of rules existing in Russia.

scholarly journals Influence of Red Mud Proportion on Circular Concrete-Filled Steel Tubular Short Columns

2020 ◽  
Vol 2020 ◽  
pp. 1-11
Author(s):  
Wu Bin ◽  
Tan Zhuoying ◽  
Li Fan ◽  
Wang Sun
Keyword(s):  
Red Mud ◽  
Longitudinal Strain ◽  
Ultimate Load ◽  
Steel Tube ◽  
Steel Tubes ◽  
Concrete Filled Steel Tube ◽  
Short Columns ◽  
Calculation Results ◽  
Concrete Filled Steel Tubes ◽  
Stub Columns

Tests on twelve circular concrete-filled steel tube stub columns with mixed red mud and three circular concrete-filled steel tube stub columns to investigate the influence of the mixed proportion of red mud on the mechanical behavior of axial compressive circular concrete-filled steel tube stub columns are reported. It is found that with the increase of red mud content, the ultimate load increases first and then decreases; on the contrary, the ultimate displacement decreases first and then increases; the specimen stress reaches the proportion limitation as the steel tube longitudinal strain is around 160 με and reaches the yield limitation as the steel tubes’ longitudinal strain is around 4400∼5000 με. The axial compressive bearing capacity empirical formulation of concrete-filled steel tubes stub columns mixed with red mud is proposed. The theoretical calculation results agree well with those experimental data.

The Seismic Behavior of Strengthened Joints between Concrete-Filled Steel Tubes and Beams Based on the Numerical Simulation Technology

2010 ◽  
Vol 150-151 ◽  
pp. 571-575
Author(s):  
Yun Peng Chu ◽  
Yong Yao ◽  
Shu Lian Xiao ◽  
Yue Chen
Keyword(s):  
Energy Dissipation ◽  
Bearing Capacity ◽  
Double Layer ◽  
Seismic Behavior ◽  
Steel Tube ◽  
Ultimate Bearing Capacity ◽  
Steel Tubes ◽  
Concrete Filled Steel Tube ◽  
Energy Dissipation Capacity ◽  
Concrete Filled Steel Tubes

As a key part in concrete-filled steel tubular frames, the seismic behavior of joints between concrete-filled steel tubes and beams needs more research because of the complexity of stress under the reciprocating load. the behavior of 9 strengthened joints connecting concrete-filled steel tube with H-shaped steel beam have been analyzed under reversed cyclic loading condition by using finite element analysis software ANSYS, and the result show that: (1) The ultimate bearing capacity, energy dissipation capacity and ductility of strengthened joint are obvious better than that of ordinary welded joint; (2) Compared to concrete-filled steel tube the ultimate bearing capacity, energy dissipation capacity and ductility of double-layer concrete-filled steel tubes are better; (3) For the joints connecting double-layer concrete-filled steel tubes with beams, the shape of inner tube have certain effect on the ultimate bearing capacity but little on the energy dissipation capacity and ductility. (4) The shape of stiffened plate has significant influence on the ultimate bearing capacity, energy dissipation capacity and ductility of nodes.

Experimental behaviour of concrete-filled steel tubes under cyclic axial compression

2019 ◽  
Vol 23 (1) ◽  
pp. 74-88 ◽  
Author(s):  
Vui Van Cao ◽  
Quoc Dinh Le ◽  
Phuoc Trong Nguyen
Keyword(s):  
Axial Compression ◽  
Maximum Stress ◽  
Axial Loading ◽  
Peak Stress ◽  
Steel Tube ◽  
Monotonic Loading ◽  
Steel Tubes ◽  
Concrete Filled Steel Tube ◽  
Loading And Unloading ◽  
Concrete Filled Steel Tubes

This study experimentally investigated the behaviour of concrete-filled steel tubes under cyclic axial compression. A total of 42 concrete-filled steel tube specimens of two groups were tested to failure. In each group, 18 specimens were subjected to three cyclic axial loading histories while three specimens were subjected to monotonic loading for comparison. The results indicated that concrete-filled steel tube specimens under cyclic axial compression failed in the form of buckling and still kept their form which was similar to the failure of specimens under monotonic loading. Effect of cyclic axial loading slightly reduced (approximately 2%–3%) the maximum stress but it increased 25% of the strain corresponding to the maximum stress. Loading and unloading moduli in post-peak stress phase were, respectively, about 70% and 85% higher than initial moduli because better interaction and confinement were resulted from the initial loading cycle. In addition, the absorbed energy exhibited a heavy dependence on strain and confinement while it was insignificantly affected by cyclic loading histories. Details and application of obtained experimental results are reported in this article.

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 Analytical Model for Restraint Strains and Self-stressed in Expansive Concrete Filled Steel Tubes (ECFST) estimation

2020 ◽  
pp. 93-98
Author(s):  
Viktar V. Tur ◽  
Radoslaw Duda ◽  
Dina Khmaruk ◽  
Viktar Basav
Keyword(s):  
Experimental Data ◽  
Experimental Studies ◽  
Steel Tube ◽  
Development Model ◽  
Steel Tubes ◽  
Concrete Core ◽  
Expansive Concrete ◽  
Proposed Model ◽  
Comparison Results ◽  
Concrete Filled Steel Tubes

In this paper, a modified strains development model (MSDM) for expansive concrete-filled steel tube (ECFST) was formulated and verified on the experimental data, obtained from testing specimens on the expansion stage. The modified strain development model for restraint strains and self-stresses values estimation in concrete with high expansion energy capacity under any type of the symmetrical and unsymmetrical finite stiffness restraint conditions was proposed. Based on proposed MSDM a new model for expansive concrete-filled steel tubes is developed. The main difference between this model and other previously developed models consists in taking into account in the basic equations an induced force in restrain that is considered as an external load applied to the concrete core of the member. For verification of the proposed model-specific experimental studies were performed. As follows from comparison results restrained expansion strains values calculated following the proposed model shows good compliance with experimental data. The values predicted by the proposed MSDM for concrete-filled steel and obtained experimental data demonstrated good agreement that confirms the validity of the former.

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