High-strength Concrete Short Columns Research Articles

Finite element modeling of square high-strength concrete short columns longitudinally reinforced with steel equal-angles under axial loading

Conventional steel bars in Reinforced Concrete (RC) square columns are utilized as longitudinal reinforcement and steel ties are utilized as transverse reinforcement for concrete confinement. The concrete confinement in RC columns with square section is less than that with circular section. Recently, Steel-Equal Angle (SEA) as longitudinal reinforcement has been investigated for square RC columns. The RC columns with SEA as longitudinal reinforcement exhibit higher strength and ductility than the RC columns with conventional steel bars as longitudinal reinforcement. However, experimental and computational investigations have been very limited on RC columns with SEA as longitudinal reinforcement. Existing studies investigated only the effects of lateral tie spacing on the performance of RC columns reinforced with SEA sections. However, the effects of the other important column parameters, such as the width and thickness of SEA sections, yield stress of SEA sections, and the concrete compressive strength, on the axial performance of RC columns reinforced with SEA sections have not been fully investigated yet. This study develops finite element (FE) models for quantifying the behavior of axially loaded square RC short concrete columns reinforced with SEA. The inelastic buckling of SEA cross-sections and the effects of concrete confinement are considered in the simulation. The accuracy of the FE analysis is verified using available test results. The influences of material and geometric properties on the compressive behavior of square RC short concrete columns incorporating SEA are studied. The results show that the model accurately estimates the behavior of square SEA reinforced concrete short columns. Moreover, the width of the SEA sections, the concrete compressive strength, and the lateral tie spacing have the most significant effects on the performance of SEA reinforced concrete columns subjected to axial loads.

Nonlinear inelastic analysis of eccentrically loaded square high-strength concrete short columns incorporating steel equal-angles

Steel-Equal Angle (SEA) has recently been utilized as longitudinal reinforcement in high-strength concrete columns to improve their strength and ductility. However, investigations have been very limited on the responses of eccentrically loaded SEA Reinforced Concrete (SEARC) columns. This paper presents the development of a computer simulation model based on fiber element discretization for determining the structural behavior of eccentrically loaded SEARC short columns. The inelastic buckling of SEA sections and the concrete confinement induced by SEA sections are explicitly taken into account. The modeling procedures are given for axial load moment-interaction curves and moment-curvature curves of SEARC columns. The accuracy of the developed fiber model is verified against the available test data. The performance of eccentrically loaded SEARC columns incorporating various design parameters is extensively investigated. It is shown that the developed computer simulation model captures well the experimentally measured responses of short SEARC columns and can be utilized in the analysis and design of such columns in practice. It has been found that the behavior of SERAC columns under eccentric loads is significantly influenced by the longitudinal steel ratio, the compressive strength of concrete, and the axial load level. The width of SEA sections and tie spacing considerably influence the ductility of the columns.

Numerical simulation of axially loaded square high-strength concrete short columns with steel equal-angles as longitudinal reinforcement

Steel Equal-Angle (SEA) can be used to replace the longitudinal reinforcement in concrete columns to improve their strength and ductility. However, as a novel concept of applying SEA as longitudinal reinforcement in concrete columns, experimental and numerical studies are very limited on the behavior of SEA Reinforced Concrete (SEARC) columns constructed with high-strength concrete. This paper presents a numerical simulation model based on the fiber-element method for computing the axial performance of square SEARC short columns loaded axially. The model accounts for the inelastic buckling of SEA sections and confinement effects provided by SEA to the confined concrete. Available test data is used to examine the accuracy of the numerical model. It is shown that there is a good agreement between numerical simulation and experimental data. The numerical model is employed to investigate the influences of important parameters on the responses of short SEARC columns subjected to axial compression. It is demonstrated that the strength and ductility of SEARC columns are significantly affected by the width of SEA sections, compressive strength of concrete, and the spacing of the lateral ties. Finally, the applicability of the design codes, including Eurocode 2, ACI 318–19, and AS 3600 for conventional reinforced concrete columns, to the design of SEARC columns is examined. The results show that the design formulae specified by AS 3600 can be used to calculate the ultimate strength of SEARC columns with reasonable accuracy.

Experimental Study of AFRP-Confined Square and Circular Concrete Columns Using Fiber Bragg Grating Sensors

An experimental investigation on square and circular high-strength concrete short columns confined with aramid fiber-reinforced polymer (AFRP) sheets was conducted in this study. Fiber Bragg grating sensors have been applied successfully in monitoring of the strains of the AFRP-confined square and circular concrete columns. The experimental results demonstrate that two types of axial force-strain curves were observed depending on the form of the column. Results show fiber Bragg grating sensors have good repeatability and the ultimate load of the circular concrete column is larger than that of the square concrete column. The interlaminar strains of AFRP and high-strength concrete have also been attained. It helps to analyze the constraint effect of the concrete column and compute the ultimate load of the square and circular concrete column.

Compressive Behavior of Circular Tubed Steel-Reinforced High-Strength Concrete Short Columns

AbstractIn this paper, a total of 12 circular tubed steel-reinforced concrete (CTSRC) short columns with high-strength concrete are constructed and tested under axial compressive load. The main var...

Experimental studies on axial load performance of high-strength concrete short columns

This paper presents the results of an experimental investigation into the axial load performance of steel-reinforced high-strength concrete short columns. The performance of a total of ten specimens is investigated, including the failure pattern, load–strain response, compressive strength and ductility. The parameters considered in this study are stirrup and structural steel arrangements. The definition of effective strength is developed to measure the compressive strength of columns due to the sudden drop of strength at peak. The ductility of columns is characterised by the ratio of after-peak and before-peak area under the curve of the axial load plotted against axial strain. Based on the experimental research, it is found that stirrups affect ductility and residual strength of columns, but not the peak strength. Structural steel influences the peak and residual strength and ductility of columns. Ductility of columns is approximately proportional to the effective confinement index if stirrups yield after peak. The effect of structural steel on ductility is more obvious when the effective confinement index is larger.

The Shear Capacity Calculation of Steel Reinforcement High-Strength Concrete Short Columns Restrained with FRP

This article aims to study the calculation for shear capacity of SRHC (Steel Reinforced High-Strength Concrete) members restrained with CFS (Carbon Fiber Sheet). Experimental study, theoretical analysis and calculation simulating are integrated in this article for the research of the shear failure characteristics and effect of various parameters on their behavior of SRHC members restrained with SFC on the basis of existed SRHC members tested results. The shear strength formula of steel reinforcement high-strength concrete short columns restrained with CFS is put forward, which based on the superposed strength method. This method on the basis of the load-deformation process of CFS is similar to hooping. The results indicate that the shear capacity of SRHC columns restrained with CFS is higher than SRHC columns. And, due to the axial compression ratio, shear span ratio and the amount of reinforcement influence the shear capacity of the FRP materials. So, these three kinds of factors are also the influencing factors of shear capacity of SRHC members restrained with CFS. The effect of the internal concrete restrained with CFS is good because of the function of CFS is equal to hooping and the strain of CFS is bigger than the strain of steel, so this simple calculation method is safe , which may be useful for further study and engineering design.

Experimental study on reinforced high-strength concrete short columns confined with AFRP sheets

This paper is aiming to study the performances of reinforced high-strength concrete (HSC) short columns confined with aramid fibre-reinforced polymer (AFRP) sheets. An experimental program, which involved 45 confined columns and nine unconfined columns, was carried out in this study. All the columns were circular in cross section and tested under axial compressive load. The considered parameters included the concrete strength, amount of AFRP layers, and ratio of hoop reinforcements. Based on the experimental results, a prediction model for the axial stress-strain curves of the confined columns was proposed. It was observed from the experiment that there was a great increment in the compressive strength of the columns when the amount of AFRP layers increases, similar as the ultimate strain. However, these increments were reduced as the concrete strength increasing. Comparisons with other existing prediction models present that the proposed model can provide more accurate predictions.

Experimental Investigation on Square High-Strength Concrete Short Columns Confined with AFRP Sheets

An experimental investigation on square high-strength concrete short columns confined with aramid fiber-reinforced polymer (AFRP) sheets is carried out in this study. Nine plain concrete specimens and 54 wrapped concrete specimens were tested under monotonic axial compressive loading. The specimens were grouped by three different grades of concrete strength. In each grade, some specimens were partially wrapped and others were fully wrapped, and the amount of wrapping AFRP sheets was varied also. Based on the experimental results, the regression formulas for strength and strain are obtained. The experimental results demonstrate that two types of axial stress-strain curves were observed depending on the form of AFRP wrapping, and the strength and ductility of the columns were increased when fully wrapped AFRP sheets, while only the strength was increased when partially wrapped AFRP sheets.

Tie-confined fibre-reinforced high-strength concrete short columns

An experimental study was carried out to investigate the behaviour of steel fibre-reinforced high-strength concrete (HSC) short columns confined by square ties under monotonically increasing concentric compression. A total of 72 confined and 24 unconfined specimens were tested in this test programme. The test variables included aspect ratio and volume fraction of crimped steel fibres, volumetric ratio, yield strength and configuration of transverse tie reinforcement and concrete strength. The effects of these variables on the uniaxial behaviour of HSC short columns are presented and discussed. The results indicate that the addition of fibres to the HSC mix prevented the early spalling of the cover and increased the load-carrying capacity and ductility of the specimens over that of comparable non-fibre columns. The effect of mixed aspect ratio of fibres on the stress–strain behaviour of confined HSC was also studied by blending the short and long fibres. It is shown that a higher gain in column strength can be affected by the addition of shorter fibres, and longer fibres can provide better enhancements in the post-peak deformability.

Behavior of Confined High Strength Concrete Columns under Axial Compression

An experimental study was carried out to investigate the behavior of high strength concrete short columns confined by circular spirals and square ties under monotonically increasing concentric compression. The test variables included volumetric ratio, spacing and yield strength of transverse reinforcement, longitudinal reinforcement ratio, lateral steel configuration, shape of cross section and concrete compressive strength. The effects of these variables on the uniaxial behavior of high strength concrete columns are presented and discussed The results indicate that more confinement is required in columns of high strength concrete than in columns of low strength concrete to achieve the desired post-peak deformability. The behavior of high strength concrete columns is characterized by the sudden spalling of concrete cover, leading to a loss of axial capacity. A comparative study of existing confinement models of high strength concrete columns was also conducted to assess their capabilities of predicting the actual test behavior. To this end, the stress-strain curves of the specimens tested in the present study were compared with the ones predicted by the various models. It is shown that Legeron & Paultre (2003) model estimates the actual experimental curves more closely as compared to the other models employed in the study.

Flexural-Shear Behavior of High-Strength Concrete Short 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.