Axial Compressive Behavior Research Articles

Axial compressive behavior of fire‐damaged RC column strengthened with ECC‐CFRP grid

AbstractTo study the axial compressive performance of fire‐damaged reinforced concrete (RC) columns strengthened by engineered cementitious composites (ECC) combined with carbon fiber reinforced polymer (CFRP) grids, eight RC columns were designed and fabricated to analyze the effects of fire exposure time, thickness of the strengthening layer, incorporation of the CFRP grid, and subjecting the strengthening layer to direct compression on the axial compressive performance of the strengthened columns by conducting fire and compressive tests. It was found that the ECC‐CFRP grid strengthening significantly increased the axial compressive load and axial deformation of the columns; the bearing capacity of the strengthened column subjected to fire for a longer period of time was lower under the same strengthening condition; when the thickness of the strengthening layer was increased, the load‐carrying capacity and axial deformation of the column were enhanced; the addition of CFRP grids could further improve the mechanical properties of the repaired column; when the strengthening layer was directly compressed, the axial deformation was significantly reduced, although the bearing capacity would be further increased. An analytical model of the strengthened column was established using the ABAQUS software, and a formula for calculating the bearing capacity of the strengthened column was derived.

Axial partial compressive behavior of round-ended concrete-filled steel tubular columns

The paper conducted 19 partially and 5 fully loaded tests on round-ended concrete-filled steel tubular (CFST) columns. These tests revealed that the ultimate strengths of round-ended CFST columns under partial load declined as the cross-sectional aspect ratio or partial compression area ratio increased. However, the use of a top plate effectively enhanced their ultimate strengths. In addition, a finite element model (FEM) was utilized to generate 487 large-size models to explore the confinement effect, stress distribution, and parametric effects. Since there are no specific design standards available for round-ended CFST columns, the paper has evaluated the applicability of design methods provided in Eurocode 4, AISC 360–16, and Chinese code GB50396 which are intended for circular, square, or elliptical CFST columns for round-ended CFST columns under partial load. However, these existing design techniques showed inaccurate and dispersed resistance predictions for round-ended CFST columns. Therefore, an effective simplified method for forecasting the resistance predictions of round-ended CFST columns under the partial load has been proposed based on the testing results and FEM analysis.

Axial Compressive Behaviours of Coal Gangue Concrete-Filled Circular Steel Tubular Stub Columns after Chloride Salt Corrosion.

The axial compressive behaviours of coal gangue concrete-filled steel tube (GCFST) columns after chloride salt corrosion were investigated numerically. Numerical modelling was conducted through the static analysis method by finite element (FE) analysis. The failure mechanism, residual strength, and axial load-displacement curves were validated against tests of the coal gangue aggregate concrete-filled steel tube (GCFST) columns at room and natural aggregate concrete-filled steel tube (NCFST) columns after salt corrosion circumstance. According to the analysis on the stress distribution of the steel tube, the stress value of the steel tube decreased as the corrosion rate increased at the same characteristic point. A parametric analysis was carried out to determine the effect of crucial variation on residual strength. It indicated that material strength, the steel ratio, and the corrosion rate made a profound impact on the residual strength from the FE. The residual strength of the columns exposed to chloride salt was in negative correlation with the corrosion rate. The impact on the residual strength of the column was little, obvious by the replacement rate of the coal gangue. A simplified design formula for predicting the ultimate strength of GCFST columns after chloride salt corrosion exposure was proposed.

Axial compression behavior of carbon fiber reinforced polymer confined partially encased recycled concrete columns.

Partially encased concrete (PEC) has better mechanical properties as a structure where steel and concrete work together. Due to the increasing amount of construction waste, recycled aggregate concrete (RAC) is being considered by more people. However, although RAC has more points, the performance is inferior to natural aggregate concrete (NAC). To narrow or address this gap, lightweight, high-strength and corrosion-resistant CFRP can be used, also protecting the steel flange of the PEC structure. Therefore, carbon fiber reinforced polymer (CFRP) confined partially encased recycled coarse aggregate concrete columns were studied in this paper. With respect to different slenderness ratios, recycled coarse aggregate(RCA) replacement ratios, and number of CFRP layers, the performance of the proposed CFRP restrained columns are reported. The RCA replacement ratio is analyzed to be limited negative impact on the bearing capacity, generally within 6%. As for the slenderness ratio, the bearing capacity increased with it. However, wrapping CFRP significantly increased the bearing capacity. Considering the arch factor, a simple formula for calculating the ultimate strength of CFRP-confined partially encased RAC columns is developed based on EC4 and GB50017-2017. By comparison with the experimental values, the error is within 10%.

Axial Compressive Behavior of FRP-Confined Compression-Cast Recycled Aggregate Concrete

Axial Compressive Behavior of FRP-Confined Compression-Cast Recycled Aggregate Concrete

Prediction of Axial Compression Behavior of Confined Concrete Columns Considering the Effect of Cryogenic Temperatures

Prediction of Axial Compression Behavior of Confined Concrete Columns Considering the Effect of Cryogenic Temperatures

Axial compressive behavior of bamboo sheet twining tube-confined concrete columns with an inner original bamboo tube

The bamboo is widely distributed around the world and the product process is developed well, the biomass bamboo fiber composite is potential to providing strong confinement for concrete, therefore in this paper, bamboo sheet twining tube-confined concrete columns with an inner original bamboo tube (BSTCB) is proposed. This column is a new structure that consists of an external bamboo fiber composite tube and an internal original bamboo tube filled with concrete between the outer and inner tubes. A total of 18 specimens were tested in axial compression. The effects of BCT thickness and original bamboo tube diameter on the mechanical properties of the specimens were analyzed. The experimental results suggested that BCT has a strong lateral confinement ability. The strength and deformability of concrete increased significantly when BCT thickness increased. When the number of BCT layers was in the range of 6–18 layers, the increase in peak stress ranged from 7.7 % to 12.8 % and the increase in ultimate strain ranged from 6.4 % to 24.0 %. The increase in the diameter of the original bamboo tubes had a positive effect to the deformation capacity, while limited effect on the concrete compressive strength. Within the change in diameter from 90 mm to 110 mm, the reduction in concrete strength is within 6.0 %, and the change in ultimate strain ranges from 8.5 % to 14.1 %. Finally, the peak stress and strain of the concrete were evaluated using the existing FRP-confined concrete model, and the full stress-strain curve of the concrete was obtained.

Experimental study and theoretical prediction of axial compression behavior in PMC-reinforced CFST columns with void defects

Polymer-modified concrete (PMC) is a promising seismic reinforcement material to improve the ultimate load carrying capacity and ductility of structures. This study investigates the reinforcing effects of PMC on voided concrete-filled steel tube (CFST) columns through axial compression tests on 21 specimens. A meticulous analysis, incorporating void arch height, steel tube thickness, and PMC reinforcement, elucidates failure modes, load-deformation behavior, and strain characteristics. The experimental results demonstrate that PMC reinforcements significantly enhance the structural behavior and load-bearing capacity, improve ductility, and prevent material detachment from excellent bonding and collaborative working properties. A novel calculation model for ultimate load capacity and lateral pressure coefficient of voided CFST columns is developed and validated. Results reveal a distinct improvement in specimen performance post PMC reinforcement, with load-displacement curves resembling intact specimens, mitigating the impact of void defects. Furthermore, PMC-reinforced specimens exhibit effective recovery of load-bearing capacity and ductility, offering a cost-effective alternative to steel tube thickening. Changes in strain and Poisson's ratio curves underscore PMC's ability to restore biaxial compression stress, enhancing stability. Prediction models, rooted in the Double Shear Unified Strength Theory, accurately anticipate ultimate bearing capacity and lateral pressure coefficient, bolstering practical engineering design and repair endeavors. In summation, this study provides comprehensive insights into PMC-reinforced voided CFST columns, facilitating informed structural enhancements and repairs.

Experimental and Numerical Simulation of Reinforced Concrete-Filled Square GFRP Tubular Columns under Axial Compression.

To investigate the axial compressive behavior of reinforced concrete-filled square glass-fiber-reinforced polymer(GFRP) tubular (RCFSGT) columns, 17 specimens were designed with variations in GFRP tube wall thickness, spiral reinforcement yield strength, and spiral reinforcement ratio. A detailed model was developed using the finite element software ABAQUS, enabling in-depth mechanistic analysis and expanded parameter studies. The results indicate that the failure types of the specimens are all manifested as GFRP square tube cracking, and the core concrete is subjected to crushing or shear failure. The inclusion of a reinforcement cage can significantly enhance the load-bearing capacity and ductility of the specimen. Furthermore, as the yield strength and reinforcement ratio of the spiral reinforcement increase, so does the load-bearing capacity of the specimen. The finite element simulation results align well with the experimental findings. As the wall thickness of the GFRP square tube increases from 2 mm to 6 mm, the load-bearing capacity improves by approximately 19.69%. With the yield strength of the spiral reinforcement rising from 200 MPa to 400 MPa, the specimen's load-bearing capacity shows an increase of approximately 7.55%. However, as its yield strength continues to increase, there is minimal change in the load-bearing capacity. When the stirrup ratio of spiral reinforcement rises from 0.33% to 2.26%, the specimen's load-bearing capacity experiences an increase of approximately 56.90%.

Experimental study on axial compressive behavior of concrete-filled corrugated steel tubular columns

Concrete-filled corrugated steel tubular (CFCST) column is a novel type of steel-concrete composite column, comprising four corrugated steel plates, four square-section steel bars at the corners, and infilled concrete. The transversely placed corrugated steel plates can effectively prevent their premature local buckling, release the axial load, and provide lateral confinement effects on the infilled concrete. This paper investigated the axial compressive behavior of CFCST columns through experimental, numerical, and theoretical approaches. Experiments were conducted on 20 specimens, focusing on their axial load-resistant behavior. The specimens demonstrated excellent axial bearing capacity, ductility, and residual bearing capacity. Besides, the mechanical behavior of corrugated steel plates throughout the loading process was analyzed through the development of the horizontal and vertical strains. Furthermore, a finite element (FE) model was developed to simulate the axial compressive behavior of CFCST columns, which was validated against the experimental data. The FE model was used to analyze the compressive behavior of each part in CFCST columns, revealing that the infilled concrete and steel bars primarily bear the axial load, while the corrugated steel plates mainly provide lateral supports to the infilled concrete. Finally, a simplified method for calculating the critical width of corrugated steel plates and a formula for the axial bearing capacity of CFCST columns were proposed. It was indicated that the limiting width-to-thickness ratio of the corrugated steel plates was larger than that of the steel elements in conventional CFST columns. These formulas were demonstrated to be accurate enough and suitable for the engineering designs.

Numerical modeling of RC column reinforced by new strategy using fiberglass tape and cloth

This paper presents the results of finite element analysis (FE) to study the axial compression behavior of reinforced concrete columns wrapped with tapes and fiberglass cloths according to different techniques using ABAQUS software. In the beginning, columns are modeled as 3D solid elements with a concrete damage plasticity model (CDPM), as the columns in this study are considered to be low compressive strength reinforced concrete and the rebar as 3D mesh elements. And once assembled, the specimen is wrapped with tape and cloth in the form of three-dimensional shell elements. Then, in order to analyze the behavior of the ultimate loads, the deformation of the confinement material, and the distribution of deformations in the concrete, the controlled displacement method used to apply the uniaxial compression loads to the specimen. Finally, a new mixed confinement model between partial confinement and complete has been proposed using a database of the results of a numerical simulation for confined concrete by fiberglass tapes and cloths. And it was found that the confinement strategy proposed in this study is very effective for the behavior of the reinforced concrete column, as the stress decreases significantly with the expansion and widening of the confinement stiffness of concrete in the plastic phase which improves the axial stress resistance.

Compressive behaviour and design of tapered lightweight concrete-filled double-skin stiffened steel tubular short columns with large hollow ratio

Tapered concrete-filled double-skin steel tubular (CFDST) members, due to their high strength-to-weight ratio and inherent spatial advantages, hold significant prospect in marine structures, such as ocean platforms and wind turbine tower. As the height and span of the column continue to increase, its weight and local buckling problems begin to emerge and become the main concerns of engineering design. To address this issue, lightweight concrete instead of normal concrete and tapered steel tubes with longitudinal stiffeners are adopted. As a result, a novel composite member, called tapered lightweight concrete-filled double-skin stiffened steel tubular short columns with large hollow ratio (LHRTL-CFDSST), is developed by the authors. In order to gain a more comprehensive understanding of the axial compression behavior of LHRTL-CFDSST members and provide an axial strength model, this study conducted axial compression tests on ten LHRTL-CFDSST short columns, investigating key parameters such as hollow ratio, longitudinal stiffeners and diameter-to-thickness ratio. The results indicated that both larger hollow ratio sections and diameter-to-thickness ratios tend to reduce the axial compressive strength and the ductility of such members, while the effect of the longitudinal stiffeners are opposite. Based on the test results, finite element (FE) model was developed and validated, and was then to conduct the mechanical analysis of the studied members, followed by a parametric study. Finally, a novel method for predicting the axial compressive strength of LHRTL-CFDSST short columns, applicable across a wide range of parameters, was proposed.

Research on the Axial Compressive Behavior of Concrete-Filled Steel Tubular Column Reinforced with Annular Stiffener

Research on the Axial Compressive Behavior of Concrete-Filled Steel Tubular Column Reinforced with Annular Stiffener

Axial compressive behavior of T-shaped welded multi-partition composite members

T-shaped welded multi-partition composite members, which are made of several rectangular concrete-filled steel tubes, are proposed to speed up the fabrication procedure. Seven half-scale T-shaped specimens were tested by considering the section height-to-width ratio and slenderness ratio. In the test, a slight torsion angle was measured when the instability failure along the asymmetric axis occurred, indicating the specimens had good torsion resistance. When the relative slenderness ratio of the specimen was larger than 0.44, the specimens failed due to the instability along the asymmetric axis. Parametric numerical analysis is conducted by considering the slenderness ratio, cross-section dimension, steel ratio, and material strength. The results show that the strength of concrete negatively impacts the ductility of the specimens, leading to a decrease of 43%, while the strength of the material positively influences the stability of the specimens. The formulas from different traditional codes are verified by the parametric numerical analysis results, indicating most codes can conservatively predict the sectional bearing capacity, but overestimate the stability coefficient of the specimens by neglecting the reduction effect of the excessive height-to-depth ratio. Recommendations are provided for calculating the stability coefficient under axial compression applicable to T-shaped welded multi-partition composite members.

Axial compressive behavior of corroded H-shaped steel columns

The unpredictability of corrosion in steel structures, especially in H-section columns, is a topic that has received limited research attention. Using Monte Carlo simulation (MCS) and finite element analysis (FEA), this study investigates the effect of random pitting corrosion on H-section steel columns' ultimate bearing capacity under axial compression. In this study, MCS was employed to address the random distribution of pitting corrosion. The reliability of MCS and FEA was validated through existing literature on compression tests of H-shaped steel columns. To comprehensively assess the detrimental effects of pitting corrosion, a total of 3650 models of H-shaped columns, each exhibiting different pitting corrosion characteristics, were subjected to analysis. These models incorporated three corrosion parameters (volume loss rate, size, and depth) and two geometric parameters (slenderness and section size). A nonlinear buckling analysis was carried out to investigate the ultimate bearing capacity of the columns. The findings indicate that a volume loss rate of 20% can cause a decrease in the column's ultimate bearing capacity by approximately 50%. Furthermore, the study reveals that at equal volume loss rates, corrosion depth and slenderness significantly influence the reduction factor, while corrosion size and section size exert a minimal impact. As a result, this paper introduces a probabilistic assessment method for estimating the reduction factor in ultimate bearing capacity for H-section steel columns. Notably, with every 10% increase in the volume loss rate, the mean reduction factor in the ultimate bearing capacity decreases by approximately 0.12.

Cross-sectional shape effect of stay-in-place formwork column on axial compressive behaviour

Experimental and numerical studies on the behavior of composite columns with prefabricated self-compacting mortar (SCM) stay-in-place (SIP) formwork and post-cast normal-strength core concrete were presented.The axial compression of twenty-eight reinforcement concrete (RC) composite columns having square or circular cross-section shapes, with formwork thicknesses of 10 mm or 15 mm, and confined with one or two layers of Carbon Fibre Reinforced Polymer (CFRP (, were tested. A finite element (FE) model was generated to simulate the stress–strain relationship, and failure mode of the column using ABAQUS software. The results show that square cross-section-shaped columns exhibited lower axial load and displacement capacities than their counterparts of equivalent circular cross-section-shaped columns. This behavior maintained consistent regardless of the use of the SCM-SIP formworks or the wrapping with CFRP fabrics. Among the various confinement systems compared in this study, the efficiency of the CFRP was the greatest. Good bonding with no peeling failure was observed between SCM-SIP formwork and core concrete, indicating the good integrity of the composite columns. Consistency between the FE model and experimental results was observed for both cross-section shapes, indicating the precise and plausible characteristics of the model to sensibly estimate the stress-strain behaviors.

Axial compression behavior of square steel tubes after artificial high-temperature cooling

This study focused on the impact of fires on steel-framed buildings and particularly emphasized the residual axial compression capacity of square steel tubes after fire suppression. To simulate fire conditions and observe the failure modes, high-temperature cooling experiments were conducted, residual axial compression capacity, and strain responses of the square steel tubes. The results demonstrated that the temperature and cooling methods significantly affected the residual strength. Below 700 °C, the residual axial compression capacity of the specimens cooled by water gradually decreased with the increasing temperatures, with a slight recovery at 900 °C. Conversely, as the temperature increased, the residual axial compression capacities of the specimens cooled with foam decreased. A simplified formula for calculating the residual axial compressive capacity of Q235 square steel tubes was proposed, and a finite-element model was established. This study utilizes simulation and parameter analysis to offer a framework for assessing the remaining axial compression capacity of Q235 square steel tubes after fire, providing valuable insights for their utilization in structural engineering and fire safety. This study aims to contribute to the reduction of economic losses and resource wastage caused by fires.

Experimental study on the axial compression behavior of circular steel tube short columns under coastal environmental corrosion

This study adopts experimental, numerical, and algorithmic methods to investigate the compressive behavior and failure mode of corroded circular steel tube short columns. The study establishes an equivalent relationship between electrochemical accelerated corrosion and natural coastal corrosion environments. The effects of current intensity, sodium chloride concentration, and energizing time on corrosion equivalent duration and mechanical properties of specimens are analyzed. The results demonstrate that the ultimate bearing capacity and energy absorption capacity of the specimens are significantly reduced with increasing current intensity and energized time. However, the NaCl concentration has minimal effect on the mechanical properties of the specimens. After natural corrosion in a coastal area with medium salinity for 19.2 years, the ultimate bearing capacity, ductility, initial stiffness, and energy absorption capacity of circular steel tube short columns decreased by 49.5 %, 63.1 %, 48.9 %, and 85.6 %, respectively. A novel corrosion pit generation algorithm is suggested to accurately simulate the distribution of corrosion pits and determine the ultimate bearing capacity of circular steel tube short columns. This algorithm demonstrates improved accuracy and stability compared to traditional simplified methods. Subsequently, a corrosion pit random generation model is developed using this method, and the accuracy of the finite element model is validated against experimental results. Furthermore, the impact of the diameter thickness ratio on the ultimate bearing capacity of corrosion specimens is thoroughly analyzed.

Axial compressive and cyclic lateral behavior of a structural masonry prism constructed from crushed COVID‐19 face masks concrete bricks

AbstractDiscarded medical face masks endanger the environment worldwide. In this study, experiments were conducted to investigate the effect of a shredded face mask (SFM) at 0% (control mix), 0.5%, 1.0%, and 2.0% by volume of concrete in the form of pieces that were 1 cm wide and 2 cm long on the properties of fresh and hardened concrete. After performing experimental testing on the materials, finite element masonry prisms with dimensions of 400 × 200 × 560 mm3 were modeled on the ANSYS platform. Four prisms with different fabric contents were numerically examined to study the compressive behavior, and 12 prisms with three different mortar joints were analyzed under an incremental horizontal load in the presence of four vertical displacements of 0.5, 1.0, 3.0, and 4.5 mm. The results revealed that increasing the SFM content in concrete led to a decrease in fresh and hardened concrete properties, including density, slump, split‐tensile strength, and compressive strength, by 9.5%, 20%, 24%, and 34%, respectively, compared with the control concrete at 0.5%. Moreover, the addition of 0.5% SFMs to the prism bricks reduced the maximum compressive load, deflection, and strain energy by 24%, 10%, and 39%, respectively. Altering the mortar type and vertical load affected the lateral cyclic behavior of the prisms. Compared with the M3 prism subjected to the same axial displacement, the M2 prism had 21.36%, 11%, 27.2%, and 10.48% higher lateral peak load, lateral peak displacement, equivalent stress, and strain energy, respectively. Furthermore, the lateral stiffness of the prism increases as the axial pressure increases. The lateral peak load of the M3 prism measured at 1.0, 3.0, and 4.5 mm axial displacement was raised by 60%, 142%, and 182%, respectively, as compared with the same prism at 0.5 mm axial displacement. The outcome provides a feasible concept for reusing masks in concrete construction with controllable strength deterioration on the masonry prism at 0.5% recycled SFM, resulting in attractive responses of these composites at the nonstructural scale

Axial compression behavior of concrete-filled prefabricated aligned steel fiber UHPC tubes

This study presents an innovative composite column system featuring exceptional ductility and versatility, suitable for replacing traditional concrete columns or UHPC composite columns. The composite column, comprised of concrete-filled aligned steel fiber ultra-high performance concrete (UHPC) tubes (ASFUTs), offers superior mechanical properties. Apart from its function as a formwork, the ASFUT provides exceptional rigidity and lateral confinement capabilities, enabling it to withstand substantial axial forces directly. Initially, steel fibers were aligned using an electromagnetic field. Computed Tomography (CT) imaging elucidated an average inclination angle of 16.36° between the fibers and the circumference of ASFUT sections. Compared to conventional UHPC, aligned steel fiber UHPC demonstrates an average 9.1 % increase in compressive strength and an average 129.67 % increase in maximum equivalent tensile. This enhancement can be attributed to the improved fiber bridging effect resulting from the orientation of fibers. Then, the mechanical properties of the concrete-filled ASFUT columns were evaluated by axial compression testing of eight specimens with different fiber contents, shapes, and orientations. The findings indicate that the ASFUTs outperform conventional concrete-filled UHPC tubes, exhibiting notable enhancements across various performance metrics. Specifically, at a fiber volume fraction of 1 %, the concrete-filled ASFUT exhibits a compressive strength, elastic modulus, ductility, and energy dissipation capacity that are 1.12 times, 1.03 times, 1.25 times, and 1.54 times respectively, in comparison to conventional concrete-filled UHPC tubes. Finally, an advanced predictive model for estimating the axial bearing capacity of ASFUT concrete columns was proposed, offering valuable insights for structural design optimization and widespread implementation.