Benchmarking of a Plasticity Material Model for Numerical Simulation of Concrete Filled Steel Tubes

Author(s):  
Robert Kroyer ◽  
Andreas Taras

<p>The popularity of composite sections increased notably in recent years due to the possibility to combine materials with individual mechanical properties beneficial for structural applications. Focusing on concrete- filled steel tubes, such members exhibit primarily an increased ultimate strength as well as a higher ductility in comparison to similar members with a homogeneous cross section made from either steel or concrete. Research issues on the structural behavior of such composite members include the interaction of the materials as well as the mechanical behavior and stochastic characteristics of the individual materials. As the materials are subjected typically to a multiaxial stress state, modelling of the material behavior is still a challenging issue in those applications. In particular for concrete, different material models were proposed in previous research for simulation of the actual behavior. This paper reports on characteristics of the structural behavior of concrete-filled steel tubes as well as on a plasticity material model for numerical simulations of this behavior. Some common approaches in application of this material model are collected and discussed, followed by an exemplary numerical application on concrete-filled steel tube specimens for the purpose of benchmarking.</p>

2020 ◽  
pp. 93-98
Author(s):  
Viktar V. Tur ◽  
Radoslaw Duda ◽  
Dina Khmaruk ◽  
Viktar Basav

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.


2015 ◽  
Vol 2015 ◽  
pp. 1-14 ◽  
Author(s):  
Yijie Huang ◽  
Yuedong Sun ◽  
Huangsheng Sun ◽  
Qing Wang

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.


Materials ◽  
2019 ◽  
Vol 12 (7) ◽  
pp. 1046 ◽  
Author(s):  
Rongling Zhang ◽  
Lina Ma ◽  
Qicai Wang ◽  
Jia Li ◽  
Yu Wang ◽  
...  

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.


2011 ◽  
Vol 121-126 ◽  
pp. 3025-3029
Author(s):  
Hui Li ◽  
Jun Deng ◽  
Jun Hong Lin

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%.


2010 ◽  
Vol 163-167 ◽  
pp. 3826-3829
Author(s):  
Feng Yu ◽  
Ping Wu

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.


2016 ◽  
Vol 2016 ◽  
pp. 1-10 ◽  
Author(s):  
Wenjing Wang ◽  
Zhenyun Tang ◽  
Zhenbao Li ◽  
Hua Ma

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.


2014 ◽  
Vol 1065-1069 ◽  
pp. 1323-1326
Author(s):  
Yi Jie Huang ◽  
Huang Sheng Sun

A review on the properties of recycled aggregate concrete filled steel tubes (RACSFT) was presented, followed by the short overview on the related researches. The uniaxial mechanical behavior, flexural performance, creep performance as well as eccentric loaded behavior of RACSFT specimens were discussed. It was found that the differences between the element made of recycled aggregate concrete (RAC) and that of natural aggregate concrete (NAC) could not be ignored. The performance of the RACFST is inferior to that of natural concrete filled steel tube (CFST). But, the RACSFT can be applied into structural elements safely. Based on the test results, it was also concluded that the RACSFT is an effective method to improve the application of RAC.


Buildings ◽  
2021 ◽  
Vol 11 (9) ◽  
pp. 397
Author(s):  
Khanh Ba Le ◽  
Vui Van Cao

This study numerically explored the torsional behavior of circular concrete-filled steel tubes (CFST) under pure torsion. Numerical models of CFSTs were developed in ABAQUS. The models were validated by comparing with the experimental results available in the literature; then, these models were used for parametric study. Based on the obtained results, the mechanism of torsional moment transferring from steel plates to CFST was presented. The results obtained from the parametric study indicated that the compressive strength of concrete marginally improved the torsional moment capacity of the CFST while concrete prevented buckling and helped the steel tubes to work more effectively. The steel strength significantly affected the torsional moment capacity of the CFST. When the yield strength of steel increased from 235 to 420 MPa, the yield torsional moment of the CFST increased by approximately 50%. The yield torsional moment capacity of the steel tube had the strongest correlation with the yield moment of the CFST, followed by the ratio of diameter to thickness of the steel tube while the parameters related to the compressive strength of concrete exhibited a poor correlation with the yield torsional moment.


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