Effects of Sustained Pre-Load on Residual Strength and Stiffness of Concrete-Filled Steel Tube after Exposure to High Temperatures

2008 ◽  
Vol 400-402 ◽  
pp. 769-774
Author(s):  
Jing Si Huo ◽  
Guo Wang Huang ◽  
Yan Xiao
Keyword(s):  
High Temperatures ◽  
Residual Strength ◽  
Axial Load ◽  
Room Temperature ◽  
Steel Tube ◽  
Load Level ◽  
Stiffness Index ◽  
Test Results ◽  
Strength And Stiffness ◽  
Stub Columns

This paper experimentally investigated the effects of axial load level on the residual strength and stiffness of concrete-filled steel tubular (CFT) stub columns which were heated and cooled down to room temperature under sustained axial load. Eight stub columns were axially loaded and heated to specified high temperatures in a purpose-built electric furnace. After the specimens cooled down to room temperature while the axial load was kept constant, the stub columns were loaded to failure. The test results show that not only the axial load level and the high temperature exposure have significant effects on the residual strength and stiffness of stub column, but the residual strength index and stiffness index of the fire-damaged CFT stub columns with pre-load are remarkably different from those without pre-load. From the test results, it is recommended that the sustained axial load effects and the fire cooling phase should be taken into consideration in assessing the fire-damaged CFT columns.

scholarly journals Restoring Force Model of Concrete-Filled Square Steel Tubular Columns with Binding Bars

2016 ◽  
Vol 10 (1) ◽  
pp. 179-188 ◽  
Author(s):  
Su Linwang ◽  
Yingtao Wang ◽  
Jian Cai ◽  
Yueling Long
Keyword(s):  
Axial Load ◽  
Peak Load ◽  
Lateral Load ◽  
Steel Tube ◽  
Load Level ◽  
Force Model ◽  
Restoring Force ◽  
Restoring Force Model ◽  
Cyclic Lateral Load ◽  
Stub Columns

This paper presents a trilinear restoring force model based on the test results of two square concrete-filled steel tubular (CFT) stub columns without binding bars and eight square CFT stub columns with binding bars subjected to constant axial load and cyclic lateral load. The effects of binding bars and axial load level on the specimens are considered to determine the feature points of the skeleton curves. Calculation formulas for the characteristic parameters of the model, including the yield load, the peak load and the ultimate load, are given by analyzing the influence of the confinement factor of steel tube, the confinement coefficient of binding bars and the axial load level. Additionally, the hysteretic rule under cyclic lateral load is confirmed. The predicted hysteretic cures and skeleton curves based on the proposed model are in good agreement with the experimental results.

scholarly journals Experimental Study of H-Shaped Honeycombed Stub Columns with Rectangular Concrete-Filled Steel Tube Flanges Subjected to Axial Load

2021 ◽  
Vol 2021 ◽  
pp. 1-18
Author(s):  
Jing Ji ◽  
Maomao Yang ◽  
Zhichao Xu ◽  
Liangqin Jiang ◽  
Huayu Song
Keyword(s):  
Bearing Capacity ◽  
Axial Compression ◽  
Axial Load ◽  
Slenderness Ratio ◽  
Steel Tube ◽  
Design Guidelines ◽  
Correction Function ◽  
Concrete Filled Steel Tube ◽  
Load Displacement ◽  
Stub Columns

The behavior of H-shaped honeycombed stub columns with rectangular concrete-filled steel tube flanges (STHCCs) subjected to axial load was investigated experimentally. A total of 16 specimens were studied, and the main parameters varied in the tests included the confinement effect coefficient of the steel tube (ξ), the concrete cubic compressive strength (fcu), the steel web thickness (t2), and the slenderness ratio of specimens (λs). Failure modes, load-displacement curves, load-strain curves of the steel tube flanges and webs, and force mechanisms were obtained by means of axial compression tests. The parameter influences on the axial compression bearing capacity and ductility were then analyzed. The results showed that rudder slip diagonal lines occur on the steel tube outer surface and the concrete-filled steel tube flanges of all specimens exhibit shear failure. Specimen load-displacement curves can be broadly divided into elastic deformation, elastic-plastic deformation, and load descending and residual deformation stages. The specimen axial compression bearing capacity and ductility increase with increasing ξ, and the axial compression bearing capacity increases gradually with increasing fcu, whereas the ductility decreases. The ductility significantly improves with increasing t2, whereas the axial compression bearing capacity increases slightly. The axial compression bearing capacity decreases gradually with increasing λs, whereas the ductility increases. An analytical expression for the STHCC short column axial compression bearing capacity is established by introducing a correction function ( w ), which has good agreement with experimental results. Finally, several design guidelines are suggested, which can provide a foundation for the popularization and application of this kind of novel composite column in practical engineering projects.

Residual Strength of Concrete Filled RHS Stub Columns after Exposure to High Temperatures

2002 ◽  
Vol 5 (2) ◽  
pp. 123-134 ◽  
Author(s):  
Lin-Hai Han ◽  
Hua Yang ◽  
Shu-Liang Cheng
Keyword(s):  
High Temperatures ◽  
Residual Strength ◽  
Axial Strain ◽  
Steel Tube ◽  
Hollow Section ◽  
Tubular Columns ◽  
Mechanics Model ◽  
Influence Of Temperature On ◽  
Strain Relationship ◽  
Stub Column

Tests are reported on twenty-six concrete filled steel tube of rectangular section after being exposed to high temperatures, to investigate the influence of temperature on section capacity and load-deformation behavior. The main parameter varied is temperature, from 20°C to 900°C. A mechanics model is described in this paper for the behaviour of concrete-filled RHS (Rectangular Hollow Section) columns after exposed to high temperatures, and is a development of the analysis (Han et al, 2001a) used when only normal temperatures apply. The predicted load versus axial strain relationship is in good agreement with stub column test results. Simplified models are derived for the section capacities and the modulus of elasticity of the composite sections. It was found in general, that the higher the exposure temperature, the higher the loss of section capacities and elastic modulus which resulted. The tests have shown the importance of the influence of high temperatures on the performance of concrete filled steel tubes. The work in this paper provides a basis for further theoretical study on the residual strength of concrete filled steel tubular columns.

Finite Element Modelling of Concrete-Filled Steel Tube Reinforced Concrete Stub Columns under Axial Compression

2013 ◽  
Vol 351-352 ◽  
pp. 138-142
Author(s):  
Zhi Bin Wang ◽  
Li Ying Liu
Keyword(s):  
Finite Element ◽  
Reinforced Concrete ◽  
Steel Tube ◽  
Fe Model ◽  
Mechanism Analysis ◽  
Test Results ◽  
Seismic Behaviour ◽  
Steel Tubes ◽  
Concrete Filled Steel Tube ◽  
Stub Columns

Concrete-filled steel tube reinforced concrete (CFSTRC) columns are currently being studied as a popular method to improve the shear strength, the ductility and the seismic behaviour of reinforced concrete (RC) columns. Owing to the complexity of confinement provided by steel tubes and stirrups, the behaviour of CFSTRC column is difficult to be accurately simulated. Thus,so far there is not a finite element (FE) model for CFSTRC columns. For studying the performance of this composite column, a FE model was developed based on the existing test results and theories. The predicted results using this FE model agree with the test results, which means that this model can be applied to carry out the further mechanism analysis.

scholarly journals Cyclic performance of circular concrete-filled steel tubular members with initial gap between tube and concrete core

2019 ◽  
Vol 23 (1) ◽  
pp. 174-189
Author(s):  
Fei-Yu Liao ◽  
Wei-Jie Zhang ◽  
Hao Han
Keyword(s):  
Axial Load ◽  
Lateral Displacement ◽  
Compressive Loading ◽  
Steel Tube ◽  
Load Level ◽  
Dissipated Energy ◽  
Lateral Loads ◽  
Concrete Core ◽  
Cyclic Behaviour ◽  
Tubular Specimens

It is common that initial gaps exist between the steel tube and the core concrete in concrete-filled steel tubular structural members, which might affect the performance of the structure. This article aims to study the effects of the gaps on the cyclic behaviour of circular concrete-filled steel tubular members. A total of 24 concrete-filled steel tubular specimens were tested under constant axial load and cyclically lateral loads, where the main testing parameters included the types of gap, the gap ratio, the axial load level and the steel ratio. The failure mode, lateral load versus lateral displacement hysteretic curve and load versus displacement envelope curve of concrete-filled steel tubular specimens with pre-designed gaps were experimentally investigated and compared with those of the reference ones without any gap. The effects of gaps on the ultimate strength, ductility and dissipated energy of the concrete-filled steel tubular members were quantitatively evaluated according to the test results. The influence of gaps on circular concrete-filled steel tubes under different loading conditions, such as axial compressive loading, pure bending, eccentrically compressive loading and cyclic lateral loading, was also compared and discussed.

scholarly journals Prediction and Analysis of the Residual Capacity of Concrete-Filled Steel Tube Stub Columns under Axial Compression Subjected to Combined Freeze–Thaw Cycles and Acid Rain Corrosion

Materials ◽  
2019 ◽  
Vol 12 (19) ◽  
pp. 3070 ◽  
Author(s):  
Zhang ◽  
Lyu ◽  
Yu
Keyword(s):  
Acid Rain ◽  
Axial Compression ◽  
Residual Strength ◽  
Steel Tube ◽  
The Other ◽  
Material Strength ◽  
Freeze Thaw ◽  
Section Size ◽  
Residual Capacity ◽  
Stub Columns

This paper presents a theoretical investigation on the safety evaluation, stability evaluation, and service life prediction of concrete-filled steel tube (CFST) structures in a Northern China area with acid rain. The finite element software ABAQUS was used to establish a numerical model, which was used to simulate the axial compression behavior of CFST columns subjected to the combined actions of freeze–thaw cycles and acid rain corrosion. The model performance was validated using the experimental results of the evaluation of mechanical properties, including the failure mode and load–displacement curve. Then, the effects of the section size, material strength, steel ratio, and combined times on the residual capacity were studied. The results show that the section size has a smaller influence on the residual strength than the other parameters and can be neglected in the design procedure. However, the other parameters, including the material strength, steel ratio, and combined times have relatively large influences on the axial compressive performance of CFST stub columns subjected to a combination of freeze–thaw cycles and acid rain corrosion. Finally, design formulae for predicting the residual strength of CFST stub columns that are under axial compression and the combined effect of freeze–thaw cycles and acid rain corrosion are proposed, and their results agree well with the numerical results.

Elasto-Plastic Analysis of Concrete-Filled Circular Steel Tubular Stub Columns after Exposed to High Temperatures

2008 ◽  
Vol 400-402 ◽  
pp. 763-768 ◽  
Author(s):  
Fa Xing Ding ◽  
Zhi Wu Yu ◽  
Jin Ping Ou
Keyword(s):  
High Temperatures ◽  
Axial Strain ◽  
Steel Tube ◽  
Fortran Program ◽  
Stress Strain ◽  
Concrete Core ◽  
Concentric Cylinders ◽  
Circular Steel Tube ◽  
Plastic Analysis ◽  
Stub Columns

Based on the research achievements of the mechanical properties of concrete at uniaxial compression and steel at uniaxial tension after exposed to high temperatures, the axisymmetric- triaxial-compressive stress-strain relationships of concrete and multiaxial stress-strain relationships of steel after exposed to high temperatures was suggested. Based on continuum mechanics, the mechanical model of concentric cylinders of circular steel tube with concrete core of entire section loaded after exposed to high temperature was determined. By applying Elasto-Plastic Analysis Method, theoretical calculation formulas for composite elastic modulus and composite stress-strain relationships of concrete-filled circular steel tubular (CFST) stub columns were proposed and a FORTRAN program was developed and the load-axial strain relationships of CFST stub columns after exposed to high temperatures were analyzed. The analysis results were in reasonable agreement with the experiment ones from references.

Finite Element Modeling of Concrete-Filled Steel Tubular Column after Exposure to Fire

2008 ◽  
Vol 400-402 ◽  
pp. 775-781
Author(s):  
Jing Si Huo ◽  
Hui Qu
Keyword(s):  
High Temperatures ◽  
Equivalent Stress ◽  
Damage Model ◽  
Steel Tube ◽  
Fe Model ◽  
Test Results ◽  
Mechanical Behaviors ◽  
Concrete Core ◽  
Composite Action ◽  
Versus Strain

A computational model, in which the effects of high temperature on steel and concrete’s properties and the composite action and interfacial properties between steel tube and concrete core were considered, was developed using ABAQUS program. Based on a damage model of concrete at ambient condition and tested stress versus strain curves of fire-damaged concrete, a new damage model of concrete after exposure to high temperatures was developed to consider the influence of high temperatures on the damage of concrete. By introducing the damage model of fire-damaged concrete, the reasonable equivalent stress-strain relations of confined concrete and a modified steel tube-concrete interface model into the ABAQUS FE model, the mechanical behaviors of the fire-damaged CFT columns and connections were simulated precisely and verified by some relative test results.

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