Axial behaviour of slender concrete-filled steel tube square columns strengthened with square concrete-filled steel tube jackets

2019 ◽  
Vol 23 (6) ◽  
pp. 1074-1086 ◽  
Author(s):  
Tao Zhu ◽  
Hongjun Liang ◽  
Yiyan Lu ◽  
Weijie Li ◽  
Hong Zhang

This article investigates the behaviour of slender concrete-filled steel tube square columns strengthened by concrete-filled steel tube jacketing. The columns were realised by placing a square outer steel tube around the original slender concrete-filled steel tube column and pouring strengthening concrete into the gap between the inner and outer steel tubes. Three concrete-filled steel tube square columns and seven retrofitted columns ranging from 1200 to 2000 mm were tested to failure under axial compression. The experimental parameters included three length-to-width ( L/ B1) ratios, three width-to-thickness ( B1/ t1) ratios and three strengths of concrete jacket (C50-grade, C60-grade and C70-grade). Experimentally, the retrofitted columns failed in a similar manner to traditional slender concrete-filled steel tube columns. After strengthening, the retrofitted columns benefitted greatly from the component materials, with their load-bearing capacity and ductility notably enhanced. These enhancements were mainly brought about by sectional enlargement and good confinement of concrete. A finite element model was developed using ABAQUS to better understand the axial behaviour of the retrofitted specimens. A parametric study was conducted, with parameters including the length of the column, thickness of the outer steel tube, strength of the concrete jacket, yield strength of the outer steel tube, thickness of the inner steel tube and strength of the inner concrete. Furthermore, the finite element model was adopted to study the behaviour of rust-damaged and post-fire slender concrete-filled steel tube square columns strengthened by square concrete-filled steel tube jacketing. A modified formula was proposed to predict the load-bearing capacity of retrofitted specimens, and the numerical results agreed well with the experiments and the finite element results of undamaged, rust-damaged and post-fire specimens. It could be used as a reference for practical application.

Author(s):  
MD Waquar Alam

Large displacements during excavation are regularly observed in Squeezing ground condition and Rock-burst condition with high overburden. The expected displacement has to be estimated prior to excavation to provide enough allowance for the displacements. The support system need to be well-suited through the estimated imposed strains. As the estimated displacements and thus the strains in the support depend upon the load-bearing capacity of support. The ratio of uniaxial compressive strength of rock mass to maximal insitu stress determines tunnel integrity in the weak region.This ratio estimates the requirements of initial lining to control strain to a stipulated level. The elasto-plastic theory may deliver definitive forecasts providing the strength limitations of rock masses are identified accurately. With the help of empirical analysis, the development of displacements for diverse advance rates and supports can be concluded. As a consequence, a quantitative finite element model based on an advanced built-in model is designed to analyse the load-bearing efficiency of initial lining although taking into consideration the time-dependent and non-linear material behaviour of initial lining. The time-dependent excavation mechanism of the drill-and-blast approach for tunnels guided by full face excavation is considered in the finite element model. The material parameters for the initial lining were computed based on case studies- (A Chibro-Khodri Hydropower Tunnel).


2020 ◽  
Vol 1 (1) ◽  
pp. 59-78
Author(s):  
Aleksandr Cherniaev ◽  
Svetlana Pavlova ◽  
Aleksandr Pavlov ◽  
Valeriy Komarov

Assessments of residual load-carrying capacity are often conducted for composite structural components that have received impact damage. The availability of a verified simulation methodology can provide significant cost savings when such assessments are required. To support the development of a reliable and accurate simulation methodology, this study investigated the predictive capabilities of a stacked solid-shell finite element model of a cylindrical composite component with a damage mechanics-based description of the intra-ply material response and a cohesive contact model used for simulation of the inter-ply behavior. Identification of material properties for the model was conducted through mechanical characterization. Special attention was paid to understanding the influence of non-physical parameters of the intra- and inter-ply material models on predicting compressive failure load of damaged composite cylinders. Calibration of the model conducted using the response surface methodology allowed for identifying rational values of the non-physical parameters. The results of simulations with the identified and calibrated finite element model showed reasonable correlation with experimental data in terms of the predicted failure loads and post-impact and post-failure damage modes. The investigated modeling technique can be recommended for evaluating the residual load-bearing capacity of flat and curved composite parts with impact damage working under the action of compressive loads.


2011 ◽  
Vol 311-313 ◽  
pp. 1884-1888
Author(s):  
Hong Yu Lin

Based on the total strain crack constitutive model and the available testing data, finite element model on three trusses were established by the finite element procedure MIDAS/FEA and the analysis were executed in order to verify the validity of constitutive model and study the static performance of combined truss. The results show that the finite element model based on total strain crack constitutive can reflect the static performance of combined truss and can carry the affective parameters analysis, which can offer theory evidence for engineering application of combined truss. The failure of three trusses were due to joint failure, however the failure modes were different and changed by the concrete filled in chord. The bearing capacity of three trusses was controlled by the jionts and the strength and stiffness of jionts were increased by the concrete filled in the chord, therefore the bearing capacity of trusses was increased while the deformation was decreased. In combined truss with steel tube and concrete filled steel tube, the concrete-filled steel tube joints can improve the bearing capacity and the steel tube joint can satisfy the requirements of plastic deformation, which have obvious advantages in the engineering application.


2014 ◽  
Vol 665 ◽  
pp. 196-202
Author(s):  
Yi Qing Guo ◽  
Ping Zhou Cao

In order to study the performance of lightweight energy-saving composite floor, the finite element models of composite floor were established, which was based on the composite floor specimens test research. The finite element models were verified rationally and correctly in the paper, through compared with the composite floor test results. The finite element model can be used to analyze the load-bearing capacity of composite floor. Various influencing factors of composite floor with simply supported end were analyzed, such as the span of self-tapping screw, the diameter of self-tapping screw, the strength of thin panel and the elastic modulus of thin panel, etc. The results show that the load-bearing capacity of composite floor increases with the increase of the number of self-tapping screw, the diameter of self-tapping screw, the strength of thin panel and the elastic modulus of thin panel, etc. The load-bearing capacity calculate formula of composite floor was proposed.


2012 ◽  
Vol 446-449 ◽  
pp. 688-694 ◽  
Author(s):  
Qi Shi Zhou ◽  
Yin Xu ◽  
Zhi Wu Yu

Nonlinear finite element model is established for the square interior constrained concrete filled steel tube column based on the research of the element type and material constitutive relation with finite element software ANSYS to find out the influence of the thickness of the steel tube, location of studs and geometry of the stirrups on the compression capacity of the short column, The results show that the compression capacity of the short column has something to do with the thickness of the steel tube and the studs, but the stirrups can eventually enhance a lot for the compression capacity as the validity is confirmed for the coherence of the results stepped from the finite element model and in test.


2013 ◽  
Vol 405-408 ◽  
pp. 1041-1045 ◽  
Author(s):  
Lian Qiong Zheng ◽  
Shu Li Guo ◽  
Ji Zhong Zhou

A simplified method using an equivalent slenderness ratio was suggested to calculate load-bearing capacity of concrete-filled steel tubular laced column in this paper. The significant differences between compressive and tensile strengths of concrete-filled steel tube were considered. The comparisons between the predicted Nuc and the tested Nue showed that the predicted method gives generally good predictions of the test results.


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