scholarly journals Short columns composed of concrete-filled steel tubes in a fire situation – Numerical model and the “air-gap” effect

2022 ◽  
Vol 15 (3) ◽  
Author(s):  
Fábio Masini Rodrigues ◽  
Armando Lopes Moreno Júnior ◽  
Jorge Munaiar Neto
Keyword(s):  
Numerical Model ◽  
Steel Tube ◽  
Air Gap ◽  
Gap Effect ◽  
Joint Analysis ◽  
Steel Tubes ◽  
Short Columns ◽  
Study Results ◽  
In Fire ◽  
Concrete Filled Steel Tubes

Abstract The increase in temperature reduces the strength of steel and concrete, in such a way that it is essential to verify concrete-filled steel tube columns in fire situations. Numerical simulations, with lower costs than laboratory tests, have great importance in checking resistance and defining simplified methods for design practice. However, peculiarities of the thermal and mechanical behavior of heated confined concrete and the air-gap effect (a phenomenon inherent to concrete-filled steel columns) must still be better understood. Therefore, this study presents the development of a numerical model performed in the ABAQUS software (Dassault Systemes SIMULIA Corp., 2014) for the thermomechanical analysis of short columns composed of circular and square concrete-filled steel tubes considering the air-gap effect. The air-gap phenomenon is presented and analyzed according to possibilities of implementation to the numerical model and, finally, the proposed numerical model is validated with experimental results presented in the literature. According to the study results, the numerical model can be used to define and adjust simplified methods for verification of composite columns in fire situation. The importance of considering the air-gap effect in numerical modeling was confirmed, taking into account that disregarding its effect may result in overestimated responses of the steel tube resistance in fire situations. Moreover, it was suggested thermomechanical joint analysis and the use of the explicit solver as a strategy to minimize processing time.

scholarly journals Analytical Assessment on the Structural Behaviour of CFST and CFDST Short Columns using Ansys

2020 ◽  
Vol 9 (1) ◽  
pp. 2505-2510
Keyword(s):  
Plain Concrete ◽  
Steel Tube ◽  
Steel Plates ◽  
Bond Quality ◽  
Structural Behaviour ◽  
Steel Tubes ◽  
Dead Weight ◽  
Short Columns ◽  
Double Skin ◽  
In Fire

Composite sections are much of the time used in structures on account of the straightforwardness and speed of erection, and prevalent in fire situation. In concrete consumed chambers the unfilled space is either filled by plain concrete or fortified concrete. In order to decrease the dead weight of composite portions and to assemble the detainment and toughness of the Concrete In-Filled Double Skinned Steel Tubular (CFDST) fragments were grasped. Two reference models, for instance, Concrete Filled Steel Tube (CFST) and Concrete In-Filled Double Skin Steel Tubes (CFDST) were endorsed and were used as references for the parametric examination. The game plan of furrowed steel plates is to improve the bond quality between the strong and the steel tubes and to manufacture the store passing on cutoff of the fragment. The parameters considered in the examination consolidated the strong assessment, thickness of the steel plate and steel grade. The composite structure under scrutiny was impersonated with a tri dimensional numerical model using the ANSYS programming, which relies upon the Finite Element Method (FEM). Examination were done reliant on the center point compressive weight. Examination of the results provoked the assurance that changing a single parameter didn't assemble as far as possible considering the way that the failure was moved to other essential parts in the composite sectionThe decisive results got from the examination of composite portion are improvement or abatement breaking point of fragment that influences the nature of the area in view of changes in the material properties. Sort of composite fragment is included to consider for feasibly picked as building structure. Finally, the stack passing on cutoff of the wrinkled composite sections are higher than the sustained fragment

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.

Research of Post-Fire Mechanical Property of Steel Fiber Reinforced Ceramsite Concrete Filled Steel Tubes after Exposure to Fire

2013 ◽  
Vol 790 ◽  
pp. 181-184
Author(s):  
Hai Lun Tong ◽  
Tian Hong Wang ◽  
Jian Qi Lu ◽  
Xin Tang Wang
Keyword(s):  
Bearing Capacity ◽  
Steel Fiber ◽  
Fiber Reinforced ◽  
Fire Load ◽  
Furnace Temperature ◽  
Steel Tubes ◽  
Compression Performance ◽  
Short Columns ◽  
Maximum Value ◽  
Concrete Filled Steel Tubes

The post-fire axial compressive behavior of a set of steel fiber reinforced ceramsite concrete filled steel tubular short columns (noted as SFCC-SSC) was experimentally studied. Effect of the maximum value of fire response temperatures of the specimens and some parameters on the axial compression performance of the specimens was especially discussed. The results show that the surface of the steel tubes after fire presented dark red for 700°Cof furnace temperature and orange red for 900°C, and there was no obvious descending segment in post-fire load-displacement curves of the most specimens subjected to fire load. It was concluded that the axial bearing capacity of the specimens aftersuffering the furnace temperature of 900°C is much less than that of the specimens not subjected to fire load, and the volume of steel fiber of 0.5% of has the greatest effect on post-fire bearing capacity of specimens of SFCC-SSC.

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.

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.

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%.

Research on the Load Capacity of Separation Concrete-Filled Steel Tubes Subjected to Eccentric Compression on Separation Side

2010 ◽  
Vol 168-170 ◽  
pp. 632-636 ◽  
Author(s):  
Xia Ping Liu ◽  
Shu Tang ◽  
Chun Hui Tang ◽  
Zuo Yong Yang ◽  
Zuo Sun
Keyword(s):  
Ultimate Load ◽  
Load Capacity ◽  
Eccentricity Ratio ◽  
Steel Tubes ◽  
Ultimate Load Capacity ◽  
Short Columns ◽  
Separation Ratio ◽  
Eccentric Compression ◽  
Experimental Parameters ◽  
Concrete Filled Steel Tubes

This paper deals with the ultimate load capacity test on 14 short columns of separation concrete-filled steel tubes (CFST) which are subjected to the eccentric compression on separate side. The experimental parameters include the separation ratio and the eccentricity ratio. The result shows that the separation ratio and the eccentricity ratio will influence the load capacity of the components of the concrete-filled steel tubes which are subjected to the eccentric compression. The confinement of steel tubes to core concrete will be continuously weakened and the ultimate load capacity of the components will be decreased obviously with both the separation ratio and the eccentricity ratio increasing gradually.

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.

Experimental Study of Performance of Self-Stress Lightweight Aggregate Concrete Filled Steel Tubes after Exposure to Fire

2013 ◽  
Vol 790 ◽  
pp. 173-176
Author(s):  
Jin Can Xu ◽  
Peng Fei Ren ◽  
Hai Lun Tong ◽  
Xin Tang Wang
Keyword(s):  
Bearing Capacity ◽  
Fire Behavior ◽  
Lightweight Aggregate ◽  
Lightweight Aggregate Concrete ◽  
Fire Load ◽  
Steel Tubes ◽  
Aggregate Concrete ◽  
Expansive Agent ◽  
Short Columns ◽  
Concrete Filled Steel Tubes

The post-fire behavior of a set of self-stress lightweight aggregate concrete filled steel tubular short columns (noted as SSLC-SSC) after exposure to fire was experimentally studied. Effect of the maximum value of fire response temperatures of the tubes and their geometric parameters on the strength and the other mechanical property of the specimens were especially discussed. The experimental results show that the specimens of SSLC-SSC have higher post-fire bearing capacity and better plastic deformation, there was no obvious descent segment in post-fire load-displacement curves of the most specimens subjected to fire load. It was concluded that the maximum response temperature of specimens has great effect on the post-fire bearing capacity of self-stress concrete-filled steel tubes subjected to fire load, and the value of self-stress corresponding to 10% of dosage of expansive agent has the greatest effect on post-fire bearing capacity of specimens of SSLC-SSC.

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