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.

Theoretical Study on Axial Capacity of CFRP Reinforced Self-Stressing Concrete Filled Steel Tubes

2011 ◽  
Vol 121-126 ◽  
pp. 3025-3029
Author(s):  
Hui Li ◽  
Jun Deng ◽  
Jun Hong Lin
Keyword(s):  
Theoretical Study ◽  
Steel Tube ◽  
Limit States ◽  
Steel Tubes ◽  
Concrete Core ◽  
Cfrp Sheets ◽  
Axial Capacity ◽  
Ultimate Equilibrium ◽  
Concrete Filled Steel Tubes ◽  
Cfrp Wrapping

Since the expansion of the cement during curing was constraint by the steel tube, the concrete core in the self-stressing concrete-filled steel tubes (SSCFST) is under tri-axially compression before applying load, which increases the axial capacity of the SSCFST. In addition, Carbon fiber reinforced polymer (CFRP) wrapping can avoid bucking of the steel tube, increase the axial capacity and improve the durability of SSCFST. This study presents a theoretical study on axial capacity of the SSCFST wrapped with CFRP sheets. Several basic assumptions are proposed. The ultimate equilibrium method was employed to analyze the axial capacity, of which two limit states, including steel tube bucking and CFRP sheets rupturing were considered. The analytical results from an example show that the initial self-stress improves axial capacity of the SSCFST by about 30% and the CFRP reinforcement improves axial capacity by about 15%.

scholarly journals Assessment of the early-age strains and stresses in 2D restrained self-stressed members

2020 ◽  
Vol 19 (4) ◽  
pp. 085-094
Author(s):  
Viktar V. Tur ◽  
Volha H. Sannikava
Keyword(s):  
Analytical Approach ◽  
Experimental Results ◽  
Development Model ◽  
Early Age ◽  
Steel Tubes ◽  
Mesh Reinforcement ◽  
Centre Of Gravity ◽  
Expansive Concrete ◽  
Iterative Procedures ◽  
Concrete Filled Steel Tubes

The paper presents the implementation of the modified strains development model (MSDM) for the two-way restrained self-stressed members such as expansive concrete-filled steel tubes and expansive concrete plane elements with arbitrary orthogonal reinforcement. The analytical approach allows defining the restrained strains and stresses in any 2D restraint conditions by following the iterative procedures and accounting for the elastic-plastic behaviour of expansive concrete at an early age. The consistency of the proposed method was confirmed by assessing the experimental results of the two series of the expansive concrete-filled steel tubes and three series of the expansive concrete plane members with mesh reinforcement in the centre of gravity.

Experimental Behaviour of Concrete Filled Steel Tubes (CFST) with Initial Concrete Imperfection Subjected to Eccentric Compression

2012 ◽  
Vol 174-177 ◽  
pp. 35-38
Author(s):  
Fei Yu Liao ◽  
Yong Jin Li
Keyword(s):  
Ultimate Strength ◽  
Steel Tube ◽  
Steel Tubes ◽  
Concrete Core ◽  
Spherical Cap ◽  
Eccentric Compression ◽  
Gap Ratio ◽  
Cfst Columns ◽  
Concrete Filled Steel Tubes ◽  
Experimental Behaviour

Gap between steel tube and concrete core could be recognized as a type of initial concrete imperfection in concrete-filled steel tubular (CFST) members. This paper is an attempt to study the effect of gap on the behaviour of concrete-filled steel tubular (CFST) columns subjected to eccentric compression. A total 14 specimens were tested and the main parameters were the gap type (circumferential gap and spherical-cap) and gap ratio. The influence of gap on the failure mode and ultimate strength of CFST columns were experimentally examined.

scholarly journals Theoretical Analysis on Mechanical Behavior of Axially Loaded Recycled Aggregate Concrete Filled Steel Tubes

2015 ◽  
Vol 2015 ◽  
pp. 1-14 ◽  
Author(s):  
Yijie Huang ◽  
Yuedong Sun ◽  
Huangsheng Sun ◽  
Qing Wang
Keyword(s):  
Mechanical Behaviour ◽  
Mechanical Model ◽  
Confining Pressure ◽  
Steel Tube ◽  
Recycled Aggregate Concrete ◽  
Recycled Aggregate ◽  
Steel Tubes ◽  
Concrete Filled Steel Tubes ◽  
Numerical Program ◽  
Core Concrete

A new mechanical model for analysing the behaviour of axially loaded recycled aggregate concrete filled steel tubes (RACFSTs) stub columns is presented in this study. The model is derived from the typical elastoplasticity, the nonlinear elastic mechanics, and the properties of materials. Based on the mechanical model, a novel numerical program is developed. The mechanical model and the numerical program are adopted to study the effect of recycled coarse aggregate (RCA) replacement percentage on RACFST mechanical behaviour. The complete load-deformation relationship of specimens, the steel tube axial and circumferential stresses, and the performance of the confined core concrete and the variation of interaction are also investigated. The analytical results indicate that this model is able to capture the mechanical behaviour of RACFST. It is also found that the axial and circumferential stresses of steel tube change nonlinearly during the loading stages. It is concluded that the behaviour of the confined core concrete is significantly influenced by the confining pressure. The steel tube confinement could improve the mechanical behaviour of RAC effectively and the RCA replacement percentage slightly changes the response of core concrete. Finally, the relations between confined core concrete and confining pressure are analysed.

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.

BEHAVIOR OF EXPANSIVE CONCRETE-FILLED STEEL TUBULAR COLUMNS UNDER AXIAL LOADINGS

2017 ◽  
Vol 4 (1) ◽  
Author(s):  
Aman Mwafy ◽  
Ame El-Dieb ◽  
Abdulaziz Lazkani
Keyword(s):  
Load Capacity ◽  
Steel Tube ◽  
Experimental Program ◽  
Outer Diameter ◽  
Test Results ◽  
Limited Information ◽  
Tubular Columns ◽  
Expansive Concrete ◽  
Axial Load Capacity ◽  
Concrete Filled Steel Tubes

Concrete-filled steel tubes (CFSTs) have been introduced to expedite construction and increase the confinement of concrete by the steel tube. While changing the confinement level through the use of expansive additives (EAs) will have an impact on the performance of CFSTs, limited information is available on the behavior of expansive concrete-filled steel tubular (ECFST) columns. The objective of this study is thus twofold: (i) to experimentally assess the behavior of axially loaded ECFSTs, and (ii) to investigate the correlation between the test results and those obtained from prediction approaches. The experimental program of this study consists of testing four 1500 mm CFST/ECFST columns with 153.6 mm outer diameter and 3 mm thickness. The ECFST specimens are divided into two subgroups with 0% and 12% EA dosage and two concrete mixtures, 16 and 37 MPa. The results indicate that the latter is the most promising mixture since it results in a significant enhancement of 64% in the axial load capacity of ECFST columns compare with CFSTs. The study also recommends employing specific confined concrete models with the existing code prediction approaches to arrive at the best correlation with test results.

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.

Uniaxial Stress-Strain Model for Concrete Confined by Rectangular Steel Tubes

2010 ◽  
Vol 163-167 ◽  
pp. 1005-1011
Author(s):  
Yue Ling Long ◽  
Jian Cai
Keyword(s):  
Triaxial Compression ◽  
Uniaxial Stress ◽  
Failure Criteria ◽  
Steel Tube ◽  
Test Results ◽  
Stress Strain ◽  
Steel Tubes ◽  
Concrete Core ◽  
Strain Behavior ◽  
The Difference

This paper presents a new model for uniaxial stress-strain relationship of concrete confined by rectangular steel tubes. The difference between concrete confinement effect provided by broad faces and that provided by narrow faces of steel tube is considered in the proposed model. The failure criteria for concrete subjected to triaxial compression is applied to estimate the ultimate strength of concrete core. The parameters of the model are determined based on the test results and the calculation of complete load-stress relationship curves is conducted for axially loaded rectangular CFT specimens using the model proposed in the paper. The concrete core strength and stress-strain behavior of rectangular CFT columns is found to exhibit good agreement with test results.

scholarly journals Bearing Capacities of Different-Diameter Concrete-Filled Steel Tubes under Axial Compression

2016 ◽  
Vol 2016 ◽  
pp. 1-10 ◽  
Author(s):  
Wenjing Wang ◽  
Zhenyun Tang ◽  
Zhenbao Li ◽  
Hua Ma
Keyword(s):  
Bearing Capacity ◽  
Axial Compression ◽  
Peak Load ◽  
Steel Tube ◽  
Specimen Size ◽  
Small Scale ◽  
Strengthening Effect ◽  
Steel Tubes ◽  
Specimen Diameter ◽  
Concrete Filled Steel Tubes

The bearing capacities of concrete-filled steel tubes are normally derived through experiments with small-scale specimens, but it is uncertain whether such derivations are appropriate for the much larger components used in practical engineering. This study therefore investigates the effect of different diameters (219, 426, 630, and 820 mm) on the axial compression of short concrete columns in steel (Q235) tubes. It is found that the peak nominal stress decreases with increasing specimen size and that the axial bearing capacity is determined by three separate components: the cylinder compressive strength of the concrete, the improvement in strength due to the confining effect of the steel tube, and the longitudinal strength of the steel tube. At peak load, increases in the specimen diameter reduce the hoop stresses in the steel tube, thereby reducing the strengthening effect of confinement. Vertical stress in the steel tube is increased with diameter; therefore, the axial bearing capacity of the steel tube is directly related to the specimen size. Size effect coefficients for these three aspects of bearing capacity are defined and used to develop a size-dependent model for predicting the axial bearing capacity of large, concrete-filled steel tubes. The model is then validated against experimental data.

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