Numerical analysis of concentrically loaded hexagonal concrete-filled steel tubular short columns incorporating concrete confinement

2021 ◽  
pp. 136943322110297
Author(s):  
Mizan Ahmed ◽  
Qing Quan Liang
Keyword(s):  
Computational Modeling ◽  
Constitutive Relations ◽  
Concrete Strength ◽  
Steel Tube ◽  
Design Equation ◽  
Design Standards ◽  
Short Columns ◽  
Concrete Confinement ◽  
Current Design ◽  
Cfst Columns

Hexagonal concrete-filled steel tubular (HCFST) columns have been used to carry large loads in tall composite buildings. Their behavior and strength are different from those of circular and square concrete-filled steel tubular (CFST) columns due to the confinement effect. This article describes a computational modeling method of nonlinear fiber analysis recognizing the concrete confinement for the response simulation of HCFST short columns subjected to axial compression. New constitutive relations of confinement for quantifying the confining stresses on the concrete confined by the hexagonal steel tube and the residual concrete strength are developed by means of analyzing existing test data. The computational modeling program written is verified by existing experimental data and then employed to ascertain the behavior of HCFST columns with important parameters. The current design standards for CFST circular columns are used to determine the strengths of HCFST columns to evaluate their applicability to the design of HCFST columns. Proposed is a new simple design equation for computing the axial capacities of HCFST columns. The computational model and the design equation proposed are shown to be accurate, and effective simulation and design tools for HCSFT stub columns that are loaded concentrically in comparisons with the current design codes.

scholarly journals Study on the Mechanical Properties of BFRP Tube Confined Concrete Short Columns under Axial Compression

2020 ◽  
Author(s):  
Xindong Ding ◽  
Shuqing Wang ◽  
Yu Liu ◽  
Zepeng Zheng
Keyword(s):  
Axial Compression ◽  
Brittle Failure ◽  
Failure Modes ◽  
Concrete Strength ◽  
Steel Tube ◽  
Confined Concrete ◽  
Test Results ◽  
Compression Tests ◽  
Short Columns ◽  
Square Steel Tube

Axial compression tests were carried out on 6 square steel tube confined concrete short columns and 6 BFRP square pipe confined concrete axial compression tests. The concrete strength grades were C30, C40, and C50. The test results show that the failure modes of steel pipe and BFRP pipe are obviously different, and the BFRP pipe undergoes brittle failure. Compared with the short columns of concrete confined by BFRP pipes, the ultimate bearing capacity of axial compression is increased by -76.46%, -76.01%, and -73.06%, and the ultimate displacements are -79.20%, -80.78%, -71.71%.

scholarly journals Fire-Resistance of Eccentrically Loaded Rectangular Concrete-Filled Steel Tubular Slender Columns Incorporating Interaction of Local and Global Buckling

2019 ◽  
Vol 19 (08) ◽  
pp. 1950085 ◽  
Author(s):  
Ghanim Mohammed Kamil ◽  
Qing Quan Liang ◽  
Muhammad N. S. Hadi
Keyword(s):  
Mathematical Model ◽  
Fire Resistance ◽  
Concrete Strength ◽  
Steel Tube ◽  
Material Behavior ◽  
Geometric Imperfection ◽  
Solution Algorithms ◽  
Global Buckling ◽  
Cfst Columns ◽  
Slender Columns

A mathematical model using the fiber approach is presented in this paper for quantifying the strength and fire-resistance of eccentrically loaded slender concrete-filled steel tubular (CFST) columns with rectangular sections incorporating the interaction of local and global buckling. The model utilizes the thermal simulator to ascertain the temperature distribution in cross-sections, and the nonlinear global buckling analysis to predict the interaction responses of local and global buckling of loaded CFST slender columns to fire effects. The initial geometric imperfection, air gap between the concrete and steel tube, tensile concrete strength, deformations caused by preloads, and temperature-dependent material behavior are included in the formulation. The computational theory, modeling procedure and numerical solution algorithms are described. The computational model is verified by existing experimental and numerical results. The structural responses and fire-resistance of CFST columns of rectangular sections exposed to fire are investigated. The mathematical model proposed is demonstrated to be an efficient computer simulator for the fire-performance of slender CFST columns loaded eccentrically.

scholarly journals Experimental analysis of bolts employed as shear connectors in circular concrete-filled tube columns

2019 ◽  
Vol 12 (2) ◽  
pp. 337-370 ◽  
Author(s):  
E. M. XAVIER ◽  
J. G. R. NETO ◽  
A. M. C. SARMANHO ◽  
L. ROQUETE ◽  
L. G. C. De PAULA
Keyword(s):  
Theoretical Analysis ◽  
Experimental Analysis ◽  
Load Capacity ◽  
Concrete Strength ◽  
Steel Tube ◽  
Experimental Results ◽  
Shear Connectors ◽  
Concrete Confinement ◽  
Push Out ◽  
Theoretical Results

Abstract This paper presents experimental and theoretical analysis of bolts employed as shear connectors in circular concrete-filled steel tube columns (CFTs). The theoretical results, obtained from ABNT NBR 16239:2013 formulations, were compared with the experimental results. A series of push-out tests were carried out, where the diameter and length of the bolts, the number of connectors and the concrete strength were varied. From the experimental results, it was observed that the equations from ABNT NBR 16239:2013 are conservative. Therefore, it is proposed an adjustment to the formulations in order to consider the concrete confinement. It was also verified that increments in the diameter and the length of the bolt increase the load capacity of the connector. However, the variation of the quantity of bolts and the concrete strength did not interfere in the load capacity.

Analysis on Bearing Capacity of Solid Multibarrel Tube-Confined Concrete Short Columns (CHS Inner and SHS Outer) under Axial Compressive Load

2011 ◽  
Vol 255-260 ◽  
pp. 151-156 ◽  
Author(s):  
Zhao Qiang Zhang ◽  
Yong Yao
Keyword(s):  
Ultimate Load ◽  
Concrete Strength ◽  
Compressive Load ◽  
Steel Tube ◽  
Confined Concrete ◽  
Unified Strength Theory ◽  
Short Columns ◽  
Circular Steel Tube ◽  
Reduction Coefficient ◽  
Square Steel Tube

By introducing the reduction coefficient of concrete strength and the equivalent restriction reduction coefficient,the non-uniform confinement force of square steel tube to its core concrete is turned to that of equivalent circular steel tube. Then the ultimate load calculation formula for the solid multibarrel tube-confined concrete short columns (CHS inner and SHS outer) is derived based on the Unified Strength Theory(UST),in which the double restriction effect and the decrease of longitudinal stress because of the hoop tensile tension are considered. The influence of intermediate principal stress on the ultimate load is studied and the failure mechanism is discussed. The applicability of the formulas is testified and the results show that the formulas have significance in exerting material potential.

scholarly journals Study on the Mechanical Properties of BFRP Tube Confined Concrete Short Columns under Axial Compression

2020 ◽  
Author(s):  
Xindong DING ◽  
Shuqing Wang ◽  
Yu Liu ◽  
Zepeng Zheng
Keyword(s):  
Axial Compression ◽  
Brittle Failure ◽  
Failure Modes ◽  
Concrete Strength ◽  
Steel Tube ◽  
Confined Concrete ◽  
Test Results ◽  
Compression Tests ◽  
Short Columns ◽  
Square Steel Tube

Axial compression tests were carried out on 6 square steel tube confined concrete short columns and 6 BFRP square pipe confined concrete axial compression tests. The concrete strength grades were C30, C40, and C50. The test results show that the failure modes of steel pipe and BFRP pipe are obviously different, and the BFRP pipe undergoes brittle failure. Compared with the short columns of concrete confined by BFRP pipes, the ultimate bearing capacity of axial compression is increased by -76.46%, -76.01%, and -73.06%, and the ultimate displacements are -79.20%, -80.78%, -71.71%.

scholarly journals Influence of steel tube thickness and concrete strength on the axial capacity of stub CFST columns

2018 ◽  
Author(s):  
Carmen Ibáñez Usach ◽  
David Hernández-Figueirido ◽  
Ana Piquer Vicent
Keyword(s):  
High Strength Concrete ◽  
Concrete Strength ◽  
High Strength ◽  
Steel Tube ◽  
Experimental Program ◽  
Ultimate Capacity ◽  
Strength Concrete ◽  
Axial Capacity ◽  
Thin Walled ◽  
Cfst Columns

In order to study the mechanical response of concrete-filled steel tubular (CFST) columns, several experimental and theoretical studies have been conducted in the last years. However, the influence of thin-walled steel tubes on the axial capacity of these composite columns is not completely stablished, especially when it is combined with high-strength concrete as infill. In this paper, the results of an experimental campaign on 9 concrete-filled steel tubular stub columns subjected to concentric load are presented. Different cross-section shapes are considered in this campaign, i.e. circular, square and rectangular. The influence of the steel tube wall thickness is analysed by including in the tests specimens with thin-walled tubes, whose behaviour needs to be studied in depth given the issues arising when working under compression. The experimental program is designed so the analysis of the results permits to drawn consistent conclusions. For each series, the steel tube thickness is the only geometric parameter modified in order to properly study its effect. Besides, two different concrete strengths were considered for the concrete infill, i.e. normal and high- strength concrete, to observe their effect on the ultimate capacity of the columns. During the tests, the specimens are subjected to axial load and the evolution of the axial displacement with the load is registered. The ultimate capacity of each specimen is obtained and an analysis of the steel tube thickness and concrete strength influence is accomplished. Finally, the study of the dependency of the failure mode on these parameters is carried out.

NUMERICAL EVALUATION OF CONCRETE FILLED STAINLESS STEEL TUBE FOR SHORT COLUMNS SUBJECTED TO AXIAL COMPRESSION LOAD

2018 ◽  
Vol 80 (2) ◽  
Author(s):  
Azrul Abd Mutalib ◽  
Mohamed Hamza Mussa ◽  
Khaleel Mohammad Khaleel Abusal
Keyword(s):  
Stainless Steel ◽  
Ultimate Strength ◽  
Ultimate Load ◽  
Load Capacity ◽  
Concrete Strength ◽  
Steel Tube ◽  
Stainless Steel Tube ◽  
Steel Tubes ◽  
Ultimate Load Capacity ◽  
Short Columns

Recently, the concrete filled stainless steel tubes (CFSST) columns are widely applied in modern construction due to its aesthetic appearance, high corrosion resistant and less construction cost. The current study aims to evaluate the behavior of CFSST column with square hollow section (SHS) numerically under axial compressive load by using ABAQUS software. A good consistency had achieved between the numerical and experimental test results in terms of load-displacement behaviour and ultimate strength with a maximum difference equal to 2%. Intensive parametric studies had been conducted to determine the effects of stainless steel tubes and concrete properties on the ultimate load capacity of CFSST column. The results proved that the stainless steel tube thickness (t) capable to increase the strength of column by143.59% at t = 10 mm as compared with t = 2 mm, whereas a slight effect had observed for the variation of stainless steel proof stress ( ). On the other hand, the higher values of concrete strength (fc′) obviously reduced the lateral expansion of CFSST column at initial load and led to increase the ultimate load capacity by 34.18 % at fc′ = 80 MPa as compared with  fc′ = 30 MPa. Furthermore, the design strengths calculated according to the Eurocode 4 for concrete filled steel tube (CFST) column appeared a good agreement with the numerical results within an average difference value 2.49%, hence, it could consider as the most rational design method to determine the ultimate strength of CFSST column.

The Experimental Study on Concrete-Filled Thin-Walled Square Steel Tube Short Columns Fixed U-Shaped Steel Bars

2011 ◽  
Vol 94-96 ◽  
pp. 962-969
Author(s):  
Hai Chao Wang ◽  
Xi Quan Xu ◽  
Li Jun Zhou ◽  
Hong Ying Zhang ◽  
Feng Lian Yang
Keyword(s):  
Concrete Strength ◽  
Testing Machine ◽  
Steel Tube ◽  
Steel Plates ◽  
Compression Process ◽  
Buckling Mode ◽  
Short Column ◽  
Short Columns ◽  
Thin Walled ◽  
Square Steel Tube

Based on the compression characteristics of the concrete-filled thin-walled square steel tube short columns, the U-shaped tie bars are designed in this paper. The U-shaped tie bars and steel pipe walls are connected with each other in T-shape in order to enhance the local stability of the walls under pressure. According to the concrete strength C30/C35/C40 and the thickness of the steel plates 1.25mm/1.75mm/2.5mm,42 short-column specimens are made, and the size of all specimens is 200mm×200mm×690mm.The bearing capacity test is done by the 500-ton electro-hydraulic serve testing machine. The strain of U-shaped tie bar and thin-walled steel are tested, and then the whole curve of compression process is obtained. The results show that the U-shaped tie bar has a very good role in bonding, and has good effects on improving buckling mode and the ductility of the components significantly. Concrete-filled thin-walled square steel tube short column fixed U-shaped tie bar has advantages on stronger post- deformability and more applicable to configuration compared with existing research achievements, and can provide a reference for engineering design.

Research on Behavior of Rectangular CFST Stub Columns with Binding Bars under Axial Compression

2013 ◽  
Vol 351-352 ◽  
pp. 790-797
Author(s):  
Hong Liang Liu ◽  
Jian Cai
Keyword(s):  
Poisson Ratio ◽  
Local Buckling ◽  
Steel Tube ◽  
Constitutive Relationship ◽  
Fe Model ◽  
Longitudinal Stress ◽  
Concrete Confinement ◽  
Central Regions ◽  
Cfst Columns ◽  
Core Concrete

The constitutive model of core concrete was proposed, which was suitable for finite element (FE) analysis of rectangular concrete-filled steel tubular (CFST) columns with binding bars. Based on the ABAQUS FE platform, the USDFLD subroutine was compiled, which could consider the changing of Poisson ratio of many materials in loading process. A FE model was developed and used to simulate the rectangular CFST columns with binding bars. The mechanical behavior were analyzed for stress versus strain relationship curves, confined effect among steel tube, core concrete and binding bars, longitudinal stress distributions of core concrete. The results show that the FE results simulated by using constitutive relationship of core concrete of this paper are in good agreement with test results. The local buckling of steel tube is delayed which can make the yield of steel tube occur before ultimate strength of specimens, the concrete confinement of the corner regions and central regions is improved, the longitudinal stress of concrete is increased and the capacity and ductility of specimens are improved, by setting binding bars and decreasing the binding bars spacing.

scholarly journals Axial Cyclic Testing of Concrete-Filled Steel Tube Columns in Diagrid Structures

2019 ◽  
Vol 2019 ◽  
pp. 1-14 ◽  
Author(s):  
Qingxuan Shi ◽  
Wenzhe Cai ◽  
Bin Wang
Keyword(s):  
Energy Dissipation ◽  
Failure Modes ◽  
Concrete Strength ◽  
Steel Tube ◽  
Concrete Filled Steel Tube ◽  
Compression Direction ◽  
Axial Cyclic Loading ◽  
Energy Dissipation Capacity ◽  
Cfst Columns ◽  
Diagrid Structure

Inclined concrete-filled steel tube (CFST) columns in a diagrid structure system can efficiently carry large vertical loads and horizontal forces. This paper presents an experimental study of the stress characteristics of engineered inclined CFST columns under axial cyclic loading. Ten specimens were tested, including two hollow steel tube (HST) columns and eight CFST columns, and the influences of loading scheme, aspect ratio, concrete strength, and steel ratio were examined. The seismic behaviours were investigated, including mechanical behaviour, failure modes and hysteretic curves, and ductility, and the interaction between the steel tube and concrete was examined as well. Better ductility and energy dissipation capacity are achieved in the tension direction, whereas higher bearing capacity and stiffness are achieved in the compression direction. Compared with hollow steel tube columns, the supporting effect of concrete on the steel tube for CFST columns in tension and the restraining effect of the steel tube on concrete for CFST columns in compression ensure higher capacity, deformability, and energy dissipation capacity.

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