Confined Concrete Columns Subjected to Axial Load, Cyclic Shear, and Cyclic Flexure—Part II: Experimental Program

2002 ◽  
Vol 99 (1) ◽  
Keyword(s):  
Axial Load ◽  
Concrete Columns ◽  
Confined Concrete ◽  
Experimental Program ◽  
Cyclic Shear

Compressive behavior of concrete-filled steel tubular columns with internal high-strength steel spiral confinement

2020 ◽  
pp. 136943322098165
Author(s):  
J.G. Teng ◽  
J.J. Wang ◽  
Guan Lin ◽  
J. Zhang ◽  
P. Feng
Keyword(s):  
Axial Compression ◽  
High Strength Steel ◽  
Axial Load ◽  
Axial Strain ◽  
High Strength ◽  
Concrete Columns ◽  
Steel Tube ◽  
Confined Concrete ◽  
Experimental Program ◽  
Cfst Columns

Concrete-filled steel tubular (CFST) columns have been extensively studied and widely used in practice. Existing research has shown that non-circular CFST columns is much less ductile than their circular counterparts, particularly when thin/high strength steel (HSS) tubes and high-strength concrete are used. To address this problem, a new form of CFST columns has recently been proposed by the first author. The new column consists of a steel tube filled with concrete that is confined with HSS spiral reinforcement typically with a yield stress exceeding 1000 MPa. These columns, referred to as confined concrete-filled steel tubular (CCFST) columns, also maintain the ease for connection to CFST or steel beams. This paper presents the results of a series of concentric axial compression tests on such columns of square cross-section to demonstrate their advantages. The experimental program included 13 CCFST columns, four CFST columns without internal spiral confinement, two hollow steel tube (HST) columns, and 11 circular HSS spiral-confined concrete columns. Three different compressive strengths and three HSS spiral pitches were examined in the experimental program. The CFST columns, HST columns, and HSS spiral-confined concrete columns were all tested under axial compression to gain a good understanding of the confinement mechanism in a CCFST column. The test results show that the new columns possess much greater ductility than those without internal spiral confinement, although the use of HSS spirals increases the steel volume by only a small percentage. It is also shown that the axial load-axial strain curve of a CCFST column can be conservatively predicted by summing the axial load-axial strain curves of the hollow steel tube without local buckling, the HSS spiral-confined concrete core, and the sandwiched concrete between the two.

scholarly journals Behavior of Square RC Short Columns with New Arrangement of Ties Subjected to Axial Load: Experimental and Numerical Studies

2022 ◽  
Author(s):  
Hazem Elbakry ◽  
Tarek Ebeido ◽  
El-Tony M. El-Tony ◽  
Momen Ali
Keyword(s):  
Reinforced Concrete ◽  
Axial Load ◽  
Concrete Columns ◽  
Experimental Program ◽  
Transverse Reinforcement ◽  
Reinforcing Bars ◽  
Rc Columns ◽  
Reinforced Concrete Columns ◽  
Short Columns ◽  
Numerical Studies

Reinforced concrete columns consume large quantities of ties, especially inner cross-ties in columns with large dimensions. In some cases, nesting of the pillars occurs as a result of the presence of cross-ties. The main objective of this paper is to develop new methods for transverse reinforcement in RC columns and investigate their effect on the behavior of the columns. The proposed V-ties as transverse reinforcement replacing the ordinary and cross-ties details are economically feasible. They facilitate shorter construction periods and decrease materials and labor costs. For this purpose, experimental and numerical studies are carried out. In the experimental program, nine reinforced concrete columns with identical concrete dimensions and longitudinal reinforcing bars were prepared and tested under concentric axial load with different tie configurations. The main parameters were the tie configurations and the length (lv) of V-tie legs. As part of the numerical study, the finite element model using the ABAQUS software program obtained good agreement with the experimental results of specimens. A numerical parametric study was carried out to study the influence of concrete compressive strength and longitudinal reinforcement ratio on the behavior of RC columns with the considered tie configurations. Based on the experimental and numerical results, it was found that using V-tie techniques instead of traditional ties could increase the axial load capacity of columns, restrain early local buckling of the longitudinal reinforcing bars and improve the concrete core confinement of reinforced concrete columns.

scholarly journals Experimental Behavior of Concrete Columns Confined by Transverse Reinforcement with Different Details

2020 ◽  
Vol 14 (1) ◽  
pp. 250-265 ◽  
Author(s):  
Mariateresa Guadagnuolo ◽  
Alfonso Donadio ◽  
Anna Tafuro ◽  
Giuseppe Faella
Keyword(s):  
Reinforced Concrete ◽  
Concrete Strength ◽  
Concrete Columns ◽  
Confined Concrete ◽  
Experimental Program ◽  
Transverse Reinforcement ◽  
Eurocode 8 ◽  
Strength Increase ◽  
Existing Buildings ◽  
Concrete Confinement

Introduction: Most of the existing reinforced concrete buildings often have columns with poor transverse reinforcement details. Models for computing the confined concrete strength were developed using experimental tests performed on specimens with transverse reinforcement typical of seismic design. The paper presents the results of an experimental program performed to investigate the effect of type, amount and pitch of transverse reinforcement on the behavior of confined concrete. Aim: The paper is also aimed at evaluating whether the current code models are suitable for estimating the confined strength of concrete in existing buildings. Methods: A total of 45 reinforced concrete columns with four volume ratios of transverse reinforcement were tested under axial loads. Type and pitch of transverse reinforcement typical of existing r/c buildings not designed according to seismic standards were considered. Therefore, columns reinforced by spiral and hoops with 135° or 90° hooks at the end are investigated for comparing their behavior. The confinement of spirals and hoops to core concrete is discussed as the amount of transverse and longitudinal reinforcement varies. Small increases in strength due to the concrete confinement were measured for hoop pitch of 150 mm (ranging between 2% and 7%), but also for hoops with 90° hook and pitch of 75 mm. Greater increments were obtained by spirals and hoops with 135° hook in the case of 75 mm pitch and when rhomboidal hoops or cross-ties were arranged in addition to the perimeter hoops. A comparison with some similar experimental results is also performed, achieving quite similar results. The mean experimental stress-strain curves are also analyzed. Results: The results show how the increase in concrete strength due to the confinement is more dependent on the transverse reinforcement pitch than the type and detail of transverse reinforcement or even less diameter of longitudinal bars. Finally, the experimental strength of confined concrete is then compared with the values provided by Eurocode 8 and the new Italian Building Code, showing that the higher the volumetric percentage of transverse reinforcement, the greater the overestimation of code models. Conclusion: An overestimation of codes up to 30% is assessed, systematically lower in the case of spirals, and higher in the case of hoops with 90° hooks at the end. The results highlight the need to develop specific equations to determine the strength increase due to the concrete confinement in the case of existing buildings with poor transverse reinforcement.

Flexural-Shear Behavior of High-Strength Concrete Short Columns

2001 ◽  
Vol 17 (4) ◽  
pp. 679-695 ◽  
Author(s):  
Armen Martirossyan ◽  
Yan Xiao
Keyword(s):  
High Strength Concrete ◽  
Axial Load ◽  
High Strength ◽  
Concrete Columns ◽  
Experimental Program ◽  
Stress Strain ◽  
Strength Concrete ◽  
Short Columns ◽  
Strain Relationship ◽  
High Strength Concrete Columns

This paper discusses the seismic performance of high-strength concrete columns. The research is a part of an ongoing comprehensive experimental program to investigate seismic design methods of high-strength concrete structures. The first stage of the program involved testing of fifteen high-strength concrete stub columns under concentric axial compression. The concrete compressive strength was about 69 MPa (10,000 psi). In addition, a large database including eighty-six similar tests conducted by other researchers was constructed, and stress-strain behavior of high-strength concrete was investigated. Based on the analysis, a stress-strain relationship for high-strength concrete columns was proposed. Secondly, six 1/3-1/2 scale high-strength concrete short columns were tested under combined axial load and cyclic shear, with double curvature condition. The primary experimental parameters included axial load ratio, longitudinal reinforcement ratio, and volumetric ratio of transverse reinforcement. The proposed stress-strain relationship was used in the analysis of the lateral force–displacement relationship for high-strength concrete columns. Moment-curvature analysis, based on proposed equivalent stress block approach, as well as plastic hinge mechanism, has been incorporated in this analytical tool. The analytical results agreed well with the primary load-deflection envelopes obtained from the tests.

Combined Bending and Axial Load in Prestressed Concrete Columns

PCI Journal ◽  
1966 ◽  
Vol 12 (3) ◽  
pp. 52-59 ◽  
Author(s):  
Paul Zia ◽  
E. C. Guillermo
Keyword(s):  
Prestressed Concrete ◽  
Axial Load ◽  
Concrete Columns
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