Steel Tubular Short Columns Research Articles

Compressive behavior of elliptical concrete-filled steel tubular short columns using numerical investigation and machine learning techniques

This paper presents a non-linear finite element model (FEM) to predict the load-carrying capacity of three different configurations of elliptical concrete-filled steel tubular (CFST) short columns: double steel tubes with sandwich concrete (CFDST), double steel tubes with sandwich concrete and concrete inside the inner steel tube, and a single outer steel tube with sandwich concrete. Then, a parametric and analytical study was performed to explore the influence of geometric and material parameters on the load-carrying capacity of elliptical CFST short columns. Furthermore, the current study investigates the effectiveness of machine learning (ML) techniques in predicting the load-carrying capacity of elliptical CFST short columns. These techniques include Support Vector Regressor (SVR), Random Forest Regressor (RFR), Gradient Boosting Regressor (GBR), XGBoost Regressor (XGBR), MLP Regressor (MLPR), K-nearest Neighbours Regressor (KNNR), and Naive Bayes Regressor (NBR). ML models accuracy is assessed by comparing their predictions with FE results. Among the models, GBR and XGBR exhibited outstanding results with high test R2 scores of 0.9888 and 0.9885, respectively. The study provided insights into the contributions of individual features to predictions using the SHapley Additive exPlanations (SHAP) approach. The results from SHAP indicate that the eccentric loading ratio (e/2a) has the most significant effect on the load-carrying capacity of elliptical CFST short columns, followed by the yield strength of the outer steel tube (\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\:{f}_{yo}$$\\end{document}) and the inner width of the inner steel tube (\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\:2{a}_{ii}$$\\end{document}). Additionally, a user interface platform has been developed to streamline the practical application of the proposed ML.

Compressive behavior of manufactured sand recycled coarse aggregate concrete-filled steel tubular short columns

To study the mechanical properties of manufactured sand recycled aggregate concrete-filled steel tubular (RACFST) columns, a total of 81 square short RACFST column specimens with different types of manufactured sand and natural sand were created and subjected to axial compression tests. The variables included sand type, core concrete strength, slenderness ratio, and steel tube thickness. The failure mode, axial load-displacement curve, axial compressive capacity, and deformation capacity of the specimens were analyzed in detail. The results indicate that the failure mode of the specimen is generally waist drum-type failure and shear-type failure, and both of them are local buckling. The load-displacement curve of the manufactured sand specimen is similar to that of the natural sand specimen, but the steel tube of the manufactured sand specimen yields later than that of the natural sand specimen. Generally, the limestone manufactured sand specimen has the highest axial compressive capacity and the best ductility ratio, while the pebble manufactured sand specimen has an axial compressive capacity similar to the natural sand specimen but a lower ductility ratio. The effects of concrete compressive strength, slenderness ratio, and steel tube thickness on specimens with manufactured sand are similar to those with natural sand. Based on the results of this experimental study, a formula for calculating the axial compressive capacity of square RACFST columns is provided.

A unified confinement-based direct design approach for novel double-skin composite columns

Concrete-filled stiffened steel tubular short columns, with cold-formed stiffened steel tubes for the outer section, have been widely used in Asia in large commercial facilities and warehouses. This paper focuses on the response of concrete-filled double-skin stiffened steel tubular (CFDSST) short columns and concrete-filled dual stiffened steel tubular (CFDST) short columns, with either square or circular inner tubes. A detailed database of existing information is assembled and presented, as well as a thorough analysis of existing design expressions. Additional examination of the concrete confinement has been undertaken which highlight the differences in behaviour between CFDSST and CFDST cross-sections. The major aim in this work is to provide a unified design approach, which accounts for concrete confinement and accounts for the material and geometric properties of the section, and offers improved accuracy over the existing approaches given in the European, American, British and Chinese design codes. The newly proposed unified confinement-based direct design approach for axially-loaded CFDSST and CFDST short columns is discussed, including the consideration given to the lateral confining pressure provided by the steel tubes. This method is shown to provide more accurate depictions of the load resistances of CFDSST and CFDST short columns relative to the international specifications, with lower scatter and greater range of applicability. It has also been shown that the CFDSST sections with a stiffened outer steel tube provides greater confinement and additional strength compared with equivalent unstiffened circular tubes of high relative tube slenderness. Given the easier fabrication and installation of beam-to-square column joints compared with circular columns, this is likely to extend their range of application in the future.

Circular concrete-filled double-skin steel tubular short columns under axial compression: An improved theoretical model and design

Existing theoretical analysis methods for concrete-filled double-skin steel tubular (CFDST) short columns generally ignore the reduction of concrete strength due to brittleness. As a result, these methods cannot accurately capture full range behavior for CFDST columns containing high-strength concrete. By focusing on the reduction effect of concrete strength in CFDST columns due to concrete brittleness, this paper proposes a reduction factor for use in design, for the first time. Based on this reduction factor, a theoretical model for axially compressed circular CFDST short columns considering non-uniform confinement effect of the sandwiched concrete is established. A substantial experimental database of 168 CFDST columns with carbon circular steel tubes is then compiled. By comparing with this database, the proposed theoretical model is shown to achieve greater accuracy than existing approaches. Utilizing this model, the influence of column parameters on the performance of the studied CFDST members are investigated and the results are discussed. It is shown that concrete strength, hollow ratio, yield strength of the outer tube, and the diameter-to-thickness ratio of the outer and inner tubes are influential to the ultimate strength and ductility of CFDST columns. However, the yield strength of the inner tube only affects the ultimate strength of CFDST columns but has a negligible influence on the ductility. Finally, utilizing the experimental and theoretical data presented, the accuracy of existing design codes for concrete-filled steel tubes for the design of CFDST members with or without considering the reduction effect of concrete strength is assessed. The results indicate that Eurocode 4 provides a more reasonable prediction result.

3D numerical study of axial compression behavior of concrete-filled steel tubular columns from mesoscopic perspective

This study investigates the axial compression behavior of Concrete-Filled Steel Tubular (CFST) short columns from a mesoscopic perspective. Concrete is regarded as a three-phase composite material consisting of aggregates, mortar, and interfacial transition zones (ITZs). The Concrete Damaged Plasticity (CDP) model was employed to simulate the nonlinear mechanical response and fracture characteristics of concrete. Verified against experimental results, the numerical model excels in realistically simulating the uniaxial compression behavior of CFST short columns. Subsequently, factors influencing the macroscopic behavior of CFST short columns were investigated. Results indicate that the random aggregate model adopted for concrete enables a more realistic prediction of the behavior of CFST short columns. Additionally, circular section steel tubes demonstrate a stronger confinement effect compared to square ones. With increasing lateral confinement, the properties of CFST short columns, such as bearing capacity and ductility, are significantly enhanced.

An analytical model for axially compressed circular concrete-filled steel tubular (CFST) short columns with varied confinement factors

Accurate evaluation of the load-strain behavior of axially compressed concrete-filled steel tube (CFST) short columns is pivotal for engineering structures, and depends on precise prediction of the hoop-axial strain response. This study introduces a two-stage hoop-axial strain relationship that incorporates the initial Poisson's ratio and elastic limit to account for the initial linearity of concrete, and a reduction coefficient to take into account the effect of concrete strength on lateral deformation properties, based on a widely used hoop-axial equation. Experimental validation across a definite concrete strength range of 28 MPa to 125.3 MPa reveals improved predictions for the dilation rate of CFST columns subjected to axial compression, particularly for those columns fabricated with high-strength concrete (> 100 MPa). Subsequently, an analytical model consisting of the proposed two-stage strain relationship, a confined concrete model with inflection-point strain and residual strength, and the biaxial stress-strain relationship of steel tube is then established to estimate the compressive behavior of circular CFST short columns. Experimental verification over a range of confinements (confinement factor from 0.289 to 2.138) demonstrates the ability of the proposed analytical model to accurately capture the load-strain curves of circular CFST short columns, especially the post-peak behavior of those with confinement factors less than 1. The performance of the established analytical model in assessing the axial load-carrying capacity of circular CFST stub columns is investigated using a database assembled from available studies.

Axial compressive behavior of reinforced hollow circular high strength concrete filled steel tubular short columns

This study aims to investigate the mechanical behavior of reinforced hollow circular high-strength concrete-filled steel tubular (RHCFST) short columns under axial compression. The axial compression test of 6 RHCFST short columns was carried out, and the bearing capacity, ductility and failure modes of the columns were analyzed. The results revealed that the failure modes of RHCFST short columns primarily included mixed failure, shear failure, and crushing failure. Comparatively, the failure modes of specimens with ordinary reinforcement exhibited a shift towards mixed failure, significant improvement in ductility, and a decrease in the increase trend of ultimate bearing capacity with the growth of steel tube thickness. Based on the test results, finite element models were developed using ABAQUS software for parameter analysis. The results demonstrated a positive correlation between the short column’s bearing capacity and parameters such as steel strength, sandwich concrete strength, steel tube thickness, and ordinary reinforcement diameter. Additionally, the initial stiffness of the short column increased with the increase of steel tube thickness. Considering the mechanical properties and engineering applicability of the member, the recommended design of steel tube yield strength, sandwich concrete strength, steel tube thickness and ordinary reinforcement diameter were given. Furthermore, the axial bearing capacity calculation formulae for RHCFST short columns were proposed. The calculated values were found to closely match both experimental and simulated values, with errors falling within 10 %. Consequently, the formulae can offer a reliable prediction of the member’s axial bearing capacity.

Numerical simulation of axially loaded circular concrete-filled steel tubular short columns with localized corrosion

Concrete-filled steel tubular (CFST) columns are widely utilized in structures owing to their cost-effectiveness, high strength, ductility, and proven fire resistance. Despite these advantages, concerns persist regarding the performance of CFST columns with locally corroded steel tubes, impeding their widespread adoption in offshore structures. This research employs three-dimensional finite element (FE) simulations for circular CFST stub columns subjected to axial compression, validated against experimental data. Verification includes full load-displacement histories, ultimate axial strengths, and failure modes. The validated FE models are then employed to assess and compare the structural behavior of CFST columns with various shapes of localized corrosion, analyzing overall load-deformation curves, interaction stress-deformation responses, and composite actions. To acquire critical data for understanding stub column behavior, 81 specimens underwent non-linear finite element analysis, with local corrosion represented by artificial notches in steel tubes. Test parameters, such as notch orientations, lengths, depths, widths, and concrete compressive strength, are varied. Results elucidate the impacts of these parameters on different aspects of stub column responses with corroded steel tubes. Furthermore, the accuracy of existing design models in predicting the ultimate axial strengths of CFST columns with corroded steel tubes is assessed. Finally, through parametric analysis of test results, a practical model is proposed and verified for computing the peak resistance of a CFST stub column with a locally corroded steel tube.

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.

Numerical analysis of circular steel–reinforced concrete-filled steel tubular stub columns

This paper presents a computational model for determining the axial responses of short circular steel–reinforced concrete-filled steel tubular (SRCFST) columns. A novel confinement model is formulated for the concrete core, which is effectively confined by the external circular steel tube and the embedded steel section. The modelling scheme of the confinement is programmed using a mathematical model that utilises fibre-element discretisation of column cross-sections. The numerical predictions are verified by experimental measurements and results obtained from finite-element analysis, demonstrating the accuracy of the modelling technology. In addition, existing concrete confinement models for concrete in circular concrete-filled steel tubular columns are assessed. The new confinement model is shown to be superior in replicating the responses of SRCFST columns. The influences of the design parameters on the column's performance are numerically investigated and ranked in order of importance through a sensitivity analysis. In this study, not only is the validity of current design standards in determining the axial load capacity of SRCFST columns examined but a new design formula is also proposed. The proposed confinement model can be employed in numerical procedures for the inelastic simulation of SRCFST columns; the design formula is suitable for use in practical design.

Mechanical behavior and design applicability of ultra-high-performance concrete-filled circular steel tubular short columns under axial compression

This paper presents the results of axial compression tests conducted on 12 short columns made of ultra-high-performance concrete-filled steel tubes (UHPCFST) with different diameter-to-thickness (D/t) ratios and steel fiber contents. The study aimed to investigate the interaction between infilled concrete and steel tubes as well as the confinement effect on the compressive behavior of UHPCFST short columns. Two types of load–displacement curves were observed in the test, which were related to the D/t ratio of the steel tube. Besides, the results showed that columns with smaller D/t ratios exhibited higher strength enhancement and better post-yield performance due to increased concrete confinement. Furthermore, the presence of steel fibers improved the post-yield ductility of the columns but did not significantly contribute to the strength enhancement. Owing to the longer elastic branch and less lateral dilation of UHPC compared to normal-strength concrete (NSC), the establishment of confining effect to UHPC core is relatively later than the yielding of steel tube, leading to a redistribution between axial stress and hoop stress. The test results were compared with current design codes, including Eurocode 4, Chinese code GB 50936, and American code AISC 360. The results showed that Eurocode 4 and GB 50936 overestimated the axial load-bearing capacity when considering the confinement effect of the steel tube, while the calculations by Eurocode 4 without considering the confinement effect and AISC 360 were closer to the test results. Therefore, the consideration of the confinement effect in design is not recommended and a reduction factor of UHPC is suggested to obtain a reliable prediction of the axial load-bearing capacity of UHPCFST short columns as safe as that of the CFST short columns infilled with NSC.

Inelastic analysis of octagonal concrete‐filled steel tubular short columns under eccentric loading

AbstractOctagonal concrete‐filled steel tubular (OCFST) columns combine the benefits of circular and square concrete‐filled steel tubular (CFST) columns so that they not only possess higher strength and ductility but also provide the ease of connection to composite beams. However, research studies have been very limited on the performance analysis of OCFST short beam‐columns subjected to eccentric loading. In this study, a fiber‐based numerical model is developed for the performance simulation of high‐strength OCFST short beam‐columns under eccentric loading. The simulation model takes into account material nonlinearities and concrete confinement induced by the octagonal steel tube. Computational methods are given that predict the axial load–moment interaction curves and moment–curvature responses of OCFST beam‐columns. The developed fiber model is verified against available test data with good accuracy. The influences of important parameters on the responses of high‐strength OCFST short beam‐columns are studied by means of utilizing the computational model. It is found that the behavior of OCFST beam‐columns is significantly influenced by the diameter‐to‐thickness ratio of the cross‐section, concrete strength, steel yield stress, and axial load ratio. Interaction equations are proposed for expressing the axial load–moment strength envelopes of the cross‐sections of OCFST beam‐columns and validated against numerical results.

Performance of round-ended recycled aggregate CFST stub columns after fire exposure

The post-fire performance of round-ended recycled aggregate concrete-filled steel tubular (RE-RACFST) short columns has been investigated experimentally and numerically. The test parameters included cross-section aspect ratios, recycled aggregate replacements and steel ratios. Twelve short columns were first heated for 90 min following ISO 834 standard fire, followed by natural cooling. Subsequently, axial compressive tests were performed to obtain the damage mode, load versus axial deformation, and strain development of the columns. The test results revealed that a higher level of recycled aggregate content resulted in decreased bearing capacity and elastic stiffness of RE-RACFSTs, and an earlier onset of the confining effect. Furthermore, finite element (FE) models were established and benchmarked against the experimental results. Parametric investigations were then conducted to study the effects of key factors on the residual load-carrying capacity. Finally, according to the experimental and FE results, a simplified formula was proposed to estimate the post-fire residual capacity of RE-RACFST stub columns.

Nonlinear analysis of square steel‐reinforced concrete‐filled steel tubular short columns considering local buckling

AbstractThis paper presents a fiber element analysis model that simulates the structural responses of square steel‐reinforced concrete‐filled steel tubular (SRCFST) short columns under concentric compression including local buckling effects. The method of effective widths is utilized to model the gradual postlocal buckling of the steel tube walls of a SRCFST column loaded axially to failure. A new confinement model is developed for the concrete based on test results, considering the confinement induced by the embedded steel section. This confinement model is incorporated into the fiber model, and its accuracy is verified by experimental results. The accuracy of various confinement models proposed for concrete‐filled steel tubular (CFST) square columns in predicting the performance of SRCFST columns is evaluated. A parametric study is performed to investigate the performance of SRCFST columns with various parameters. The applicability of the design formulas specified in current standards for CFST columns to the design of SRCFST columns is examined. A formula is proposed to predict the strength of SRCFST short columns. The developed inelastic simulation model, confinement model, and design formula are found to yield performance predictions of SRCFST columns with good accuracy.

Confinement-based direct design method for fibre reinforced polymer confined CFST short columns

The paper presents a detailed analysis of the behaviour of circular and square concrete filled steel tube (CFST) short columns strengthened externally with carbon or glass fibre reinforced polymer sheets (CFRP or GFRP, respectively). A thorough review of existing test information is presented and discussed, and the most salient parameters in terms of the overall strength are identified. There are a large number of influential and inter-related parameters which affect the load-carrying capacity, including the geometry, cross-sectional shape, type of steel, concrete strength, boundary and loading conditions, and type of FRP. It is shown that existing design approaches do not reliably predict the strength for the full range of possible parameters. Therefore, this paper proposes a new design model to calculate the axial compressive strength of FRP-confined concrete filled steel tubular (CFST) short columns with either a circular or square cross-section. The method accounts for the various complexities which affect the behaviour, yet presents a user-friendly, performance-based design expression. It is based on an evaluation of the lateral confining pressure provided by the both the FRP and the steel tube to the concrete core. This is employed in the confinement-based direct resistance calculations. The paper validates the approach by comparing its capacity predictions with a large database of experimental results and alternative design models available in the literature. The results show that the proposed model provides much accurate strength predictions with greater reliability for the full range of parameters examined, than existing methods.

Test and design of rectangular steel-reinforced concrete-filled stainless steel tubular short columns

In this study, the compressive behaviour of rectangular steel-reinforced concrete-filled stainless steel tubular (SRCFSST) short columns was investigated. Compressive tests on 10 rectangular SRCFSST stub columns and 2 rectangular concrete-filled stainless steel tubular (CFSST) counterparts were performed to study the effect of steel ratios and steel sectional shape on the compressive performance of SRCFSST short columns. Compression test results showed that the rectangular SRCFSST column has higher carrying capacity, deformability, and ductility than the rectangular CFSST column. A refined finite element (FE) model of the rectangular SRCFSST stub column was created. According to the FE study, adding carbon profiled steel to rectangular CFSST significantly improved confinement of concrete. Thus, ductility and bearing capacity of the composite column were greatly improved. The carrying capacity, peak strain, and compressive stiffness of the rectangular SRCFSST short column were evaluated using FE parametric analysis. Finally, design methods of the carrying capacity, peak strain, and compressive stiffness of the SRCFSST short column were recommended or refined.

Behavior of embedded steel profile ultra-high performance concrete-filled stainless steel tubular short columns under axial compression

This study investigated the behavior of ultra-high performance concrete-filled stainless steel tubular columns with embedded steel profiles (ESUHPCFSST) under axial compression. Six short columns were designed with the parameters of diameter-to-thickness ratio and embedded steel profile ratio. Axial compression tests were conducted to investigate the failure modes, failure mechanisms, and the impact of relevant parameters on the mechanical properties of the specimens. A finite element model was developed and validated against the experimental results to enable a more comprehensive parameter analysis. The results indicate that the failure of the specimens always initiates from the steel profile flange and gradually extends to the external stainless steel tube. The initial stiffness, ultimate bearing capacity, and ductility of the specimens increase with decreasing diameter-to-thickness ratio and increasing embedded steel profile ratio. The strength of the embedded steel profile positively correlates with ultimate bearing capacity and ductility. Higher concrete strength improves ultimate bearing capacity but reduces ductility. Finally, a bearing capacity prediction model for ESUHPCFSST columns is proposed based on the experimental and finite element results, which guides the engineering application of such structures.

A unified design equation for square and rectangular concrete-filled steel tubular short columns

This paper develops a new unified design equation to estimate the axial compressive strength of square and rectangular concrete-filled steel tubular (CFST) short columns. The following four steps are involved: (i) compiling an experimental database consisting of 348 square and 113 rectangular CFST short columns, (ii) conducting 245 parametric analyses using benchmarked finite element (FE) models to address the gaps in the database, (iii) evaluating existing design equations and identifying their insufficiencies, and (iv) proposing and validating the new design equation. As compared with the existing design equations, the proposed design equation has the following advantages: (i) allowing a fast and convenient estimation of the axial compressive strength of square and rectangular CFST short columns, (ii) getting rid of the calculation of the section slenderness, and (iii) extending the codified material strength limits of the concrete infill and steel tube, i.e., it is suitable to square and rectangular CFST short columns with the compressive strength of the concrete infill up to 150 MPa and yield stress of steel tube up to 1000 MPa.

Artificial neural network model for strength predictions of CFST columns strengthened with CFRP

This paper presents an optimised Artificial Neural Network (ANN) model for predicting the ultimate axial strengths of concentrically loaded Concrete-Filled Steel Tubular (CFST) short and slender columns strengthened with Carbon Fibre-Reinforced Polymer (CFRP). Since experimental data on CFRP strengthened CFST columns is limited, an accurate Finite Element (FE) model is developed and used to provide additional numerical data. A multi-layered feed-forward back-propagation network is proposed, optimised, and trained using the results of 76 experimental tests and 450 generated FE models. The accuracy of the ANN model is assessed through comparing its computed results with experimental data. A reliability analysis is performed using Monte Carlo Simulation (MCS) to evaluate the safety of the solutions computed by the ANN model. ANN-based equations and Graphical User Interface (GUI) are developed based on the trained ANN model for the determination of the ultimate axial strengths of CFST columns. The results show that the developed ANN model is capable of accurately predicting the ultimate axial strengths of CFRP strengthened CFST columns with a high degree of accuracy.

Axial compressive performance of ultra-high strength concrete-filled dual steel tubular short columns with outer stiffened tubes and inner circular tubes

Previous literature shows that studies of ultra-high strength concrete-filled dual steel tubular (UHS-CFDST) short columns under concentric compression are rare, and there is no relevant research on ultra-high strength concrete-filled dual stiffened steel tubular (UHS-CFDSST) short columns. In addition, existing design specifications do not include ultra-high strength concrete (UHSC). Therefore, the axial compressive response and resistance of UHS-CFDSST short columns are investigated herein. First, the behaviour of CFDSST columns with normal-strength concrete (NSC) was replicated by finite element (FE) modelling using ABAQUS software. Additionally, the experimental results of square and circular ultra-high strength concrete-filled steel tubular (UHS-CFST) short columns were collected from the available literature, and finite element (FE) modelling is performed accordingly. The results showed that the applied concrete constitutive model is suitable for UHSC and the modelling strategy for UHS-CFST columns and CFDSST columns with NSC is suitable for UHS-CFDSST short columns. Accordingly, parametric studies were carried out on UHS-CFDSST to investigate the effects of geometrical and material properties of different steel and concrete components on the performance of these columns. It was found that the strength of the sandwiched concrete has the greatest effect on the resistance of the columns compared to the other parameters considered. Finally, the axial resistance of the UHS-CFDSST short columns was compared to the resistances calculated by using the European, British and Chinese codes, and it was found that the Chinese code gives the best results.