Concrete-filled Steel Tubular Research Articles

Effects of Out-of-Plane Deformation of the Base Plate on the Structural Behavior of an Exposed Column Base

This study explores the behavior of exposed column bases in concrete-filled steel tubular (CFST) and steel structures, with a focus on cases where base plates yield due to out-of-plane deformation. Understanding these mechanisms is crucial for improving the design and safety of these structures. Experimental tests and numerical analyses were conducted on four specimens to investigate their lateral load versus drift angle behavior. The tests demonstrated that base plates exhibited sufficient deformation capacities and enhanced hysteresis characteristics. Finite element method (FEM) analysis successfully traced the load–deformation relationships observed in the tests, providing detailed insights into stress distribution on the base plates. Based on these analyses, a simplified calculation method was proposed to evaluate the horizontal strength of exposed column bases. The proposed method showed excellent agreement with the test results, highlighting its potential as a practical tool for structural design.

Numerical Modelling of the Punching Shear Response of Shearhead Connections between a CFT Column and a Flat Reinforced Concrete Slab

In this article, the punching shear response of shearhead connections between a Reinforced Concrete (RC) flat slab and interior Concrete-Filled steel Tubular (CFT) columns under static load is investigated by using a 3D nonlinear finite element modelling approach. The accuracy of the numerical model is verified against recent experimental results by comparing the results of the load–displacement relationship, failure models and cracking patterns. Based on validated numerical models, parametric investigations are conducted to examine the effects of slab thickness, concrete compressive strength, length of shearhead arm, size of shearhead cross section and flexural reinforcement ratio on the punching shear response of the connections. Then, some recommendations are given for the design of the effective parameters of shearhead connections, particularly focusing on the effective length and cross-section size of shearhear arms. Finally, a design equation considering the effect of the effective length of shearhead arms and flexural reinforcement ratio is proposed to predict the punching shear strength of shearhead connections. The comparison of punching shear strengths predicted by the proposed equation and some design codes shows that the proposed equation can predict the punching shear strength of shearhead connections more accurately than those from ACI 318-14 and Eurocode 2.

Test and Analysis for Shearing Behavior of Circular CFST Columns

Concrete-filled steel tubular (CFST) structures are well known to possess high strength and ductility. CFST members are used under complex stress states, such as beam–columns, piers, caissons, or other foundation components. Recommendations for the design and construction of concrete-filled steel tubular (CFST) structures were published in 1997 and revised in 2008 in Japan. In the recommendations, calculation methods for the axial strength and flexural strength of CFST columns were established on the basis of experimental results of more than 400 specimens; however, the test results of the columns that failed in shear referred to only 12 specimens in the recommendations. It is necessary to accumulate experimental data on the shear strengths and behaviors of CFST columns. Tests and analyses have been carried out on eight circular CFST column specimens with a shear span ratio of 0.75. The diameter-to-thickness ratio of the steel tube is approximately 34. The shearing capacities of the tests were underestimated by over 20% errors using the calculation method of the CFST Recommendations in Japan. The load versus deformation relations obtained by the tests were well traced by 3D-FEM analysis. The shearing capacities were estimated as an average of 12% errors using 3D-FEM analysis.

Residual axial bearing capacity of square high-strength concrete-filled steel tubular columns after transverse impact loading

In recent decades, the performance of concrete-filled steel tubular (CFST) members under impact loads has received much attention. Serving as the main load-bearing components in structures, CFST members, especially those using high-strength materials, are expected to maintain their capacities in supporting the superstructures during and after potential extreme events to avoid severe consequences. The post-impact residual axial bearing capacities of square high-strength concrete-filled steel tubular columns were therefore determined to be the focus of this study. Axial loading experiments were conducted on 12 square high-strength CFST specimens with impact-induced damage, and a finite element (FE) model was developed in which both the impact loading process and the post-impact axial loading process were involved. Based on the developed FE model, parametric studies were then carried out to evaluate the influence of the material properties, the cross-sectional characteristics, the initial axial load ratio and the impact energy conditions on the post-impact residual bearing capacities of high-strength CFST columns. A total of five hundred random CFST models were modelled and analysed to ascertain the mutual relationships among the impact energy, the maximum impact deformation (support rotation) and the post-impact residual bearing capacities quantitatively, which are anticipated to facilitate both the rapid performance assessment of the impacted damaged (deformed) square CFST columns after the occurrence of impact events and the performance-based impact-resistant design in advance against such accidents.

Numerical analysis and design of axially-loaded concrete-filled stainless-clad bimetallic steel tubular slender columns

Concrete-filled stainless-clad bimetallic steel tubular (CFBST) structures with stainless-clad bimetallic steel outer tubes combine the cost-effectiveness and high corrosion resistance of stainless-clad steel with the excellent load-bearing capacity inherent in traditional concrete-filled steel tubular (CFST) structures, making them well-suited for applications in demanding marine environments. This paper presents a comprehensive numerical study on CFBST slender columns with circular hollow section (CHS) outer tubes under axial compression. Finite element (FE) models were established and validated by comparing the load-axial displacement curves, ultimate loads, and failure modes obtained from the FE models with the existing experimental results. By employing the validated FE models, an extensive parametric analysis comprising 1120 models was undertaken to investigate the influence of length-diameter ratios, clad ratios and wall thicknesses of stainless-clad bimetallic steel outer tubes, as well as concrete strengths on the flexural buckling behavior of CFBST slender columns. The applicability of existing design codes for conventional CFST systems, including the European Standard EN 1994–1-1, Australian Standard AS/NZS 5100, American National Standard ANSI/AISC 360-22, as well as two Chinese Codes GB 50936-2014 and GB/T 51446-2021 was evaluated. It has been observed that the method outlined in EN 1994–1-1 is recognized for its accuracy in calculating flexural buckling resistance. However, it tends to yield overconservative predictions within the relative slenderness range of 0.2 to 0.35, where buckling effects are already considered. Consequently, a modification to EN 1994–1-1 has been proposed to adjust the limiting non-dimensional slenderness for CFBST slender columns to 0.35, thereby enhancing the accuracy and consistency in design capacity predictions.

Performance of concrete-filled steel tubular stub columns reinforced with annular stiffener under axial compression: Experiment, simulation and design

This paper presents a study focusing on the structural behavior of a newly developed concrete-filled steel tubular (CFST) stub column reinforced with annular stiffener under axial compression. The annular stiffener is fabricated by curved steel plate with the circumferential plate serving as the connecting interface. The compression test was carried out on the new composite column and CFST counterparts, and the experimental findings reveal that the columns demonstrate superior capacity, stiffness and ductility than CFST columns. A validated finite element (FE) model was developed to comprehensively analyze the mechanism of composite action between components. Besides, parametric analyses were conducted to explore the influence of different parameters on the axial behavior of the members. Then, a physical and mechanical model with consideration of stiffener-contributions is proposed to predict the axial strength of stub columns. The results demonstrate that the FE modeling developed simulates well the structural behavior of the composite columns. The parametric studies suggest that the utilization of high-strength and thick wall-thickness circumferential plate is inefficient and uneconomical. Furthermore, the comparison results show the proposed design model possesses high accuracy and is in good agreement with both experimental and numerical results.

In-plane stability behaviours of concrete-filled steel tubular catenary arches under different loading conditions

Concrete-filled steel tubular (CFST) catenary arches, renowned for their superior loading-bearing efficiency due to the alignment of the arch axis with the thrust line, have become the predominant choice for large-span arch bridges over the past decade. However, research on CFST catenary arches remains limited, with most studies focusing on the in-plane strength of circular and parabolic arches. And the existing design methods are tailored to a narrow range of loading conditions, which raises concerns about their applicability to CFST catenary arches. Therefore, this paper addresses this gap by designing and testing six CFST catenary arches under three different loading conditions (quarter-point concentrated load, mid-span concentrated load, and five-point concentrated loads). The failure modes, load-displacement curves, cross-sectional strain and stress development, and confinement effects were compared and analysed among the loading conditions. Additionally, the finite element (FE) models using beam elements were developed and verified against the test results to conduct a parametric analysis. The influence of arch axis coefficient, slenderness ratio, rise-to-span ratio, and steel ratio on the in-plane strength of the CFST catenary arches under seven different loading conditions was discussed. Finally, by accounting for the non-uniform distribution of internal forces along the arch rib, a lower-bound design formula for the in-plane strength of CFST catenary arches under various loading conditions was proposed, and comparisons with numerical results show that the proposed method can provide conservative predictions.

Experimental and analytical study on CFST column-steel beam joints with stiffening ring and stirrups under high axial compression ratio

Super high-rise structures frequently employ concrete-filled steel tubular (CFST) column-steel beam joints with stiffening ring because of its superior performance. This study examined the structural behavior of high axial compression ratio stiffening ring joints with stirrups in the column. Three 1/2-scaled joints with different stirrup arrangements and axial compression ratios were designed and tested. Apart from analyzing the hysteresis behavior, skeleton curve, stiffness degradation, energy dissipation, and steel strain of each specimen, an investigation was conducted into the failure mechanisms of the specimens under low cycle reciprocating load on the beam end. Furthermore, a three-dimensional nonlinear solid finite element (FE) model was developed for the joint. The results of the FE analysis and the experimental data agreed well regarding failure modes, hysteresis curves, and steel strain. Furthermore, the energy dissipation allocation mechanism of joints with various parameters was revealed. The results show that the seismic performance of the stiffening ring joint with stirrups was excellent, and stirrup confinement effectively improved the seismic performance of stiffening ring joints. Under a high axial compression ratio of 0.8, the joint with stirrup exhibited bending failure at the beam end, avoiding the phenomenon of column end bending failure in traditional specimens. In addition, the stiffening ring joint underwent a transition from beam energy dissipation to column energy dissipation when the beam-column flexural capacity ratio reached 1.39. The study's findings can serve as a guide for engineers using stirrups in square CFST column-steel beam joints with stiffening rings.

Compressive Behaviour of Circular High-Strength Self-Compacting Concrete-Filled Steel Tubular (CFST) Stub Columns Under Chloride Corrosion: Numerical Simulation

This paper investigates the strength and behaviour of high-strength self-compacting concrete-filled steel tubular (HSSC-CFST) stub columns under axial compression. HSSC-CFST columns are high-performance structural members with wide applications in engineering structures. Nevertheless, relevant studies have commonly focused on the mechanical performance of HSSC-CFST in indoor environments. A finite element (FE) model was developed to predict the axial load capacity of HSSC-CFST stub columns subjected to chloride corrosion. According to this, several crucial geometric and material parameters were designed to investigate the influences on strength, initial stiffness, and ductile performance. Moreover, the analysis on failure mechanisms was investigated by N-ε curves and stress development in the whole loading process. The impacts of key parameters on the reduction factor of axial load capacity were also identified. The numerical analysis results indicate that the axial strength of HSSC-CFST stub columns under chloride corrosion was significantly heightened by increasing the strength of core self-compacting concrete, while contrary results were found with the increase in the steel ratio and yield strength of the steel tube. Lastly, design recommendations for the axially loaded HSSC-CFST were presented by modifying the design codes in CECS104-99. The proposed model is shown to be able to estimate the axial load-bearing capacity of HSSC-CFST stub columns more accurately.

An Assessment of the Bearing Capacity of High-Strength-Concrete-Filled Steel Tubular Columns Through Finite Element Analysis

This work aimed to evaluate the accuracy of analytical models for predicting the behavior of concrete-filled steel tubular (CFST) columns via finite element analysis coupled with physical nonlinearity. The methodology involved an extensive review of experimental tests from the literature, numerical modeling of columns with different configurations, and a comparison of the results obtained with available experimental data. Several characteristics were evaluated, such as the load capacity, confinement factor, and relative slenderness. The numerical model agreed well with the experimental results, with a less than 10% relative error. The results indicated that analytical models of the Chinese (GB 50936) and European (EC4) codes overestimated some load capacity values (up to 14.9% and 8.7%, respectively). In comparison, the American (AISC 360) and Brazilian (NBR 8800) standards underestimated the ultimate loads (23.3% and 31.6%, respectively). An approach coefficient β is proposed, contributing to safer and more efficient design practices in structural engineering.

Experimental and Numerical Investigation on the Bearing Capacity of Axially Compressive Concrete-Filled Steel Tubular Columns with Local Corrosion

This study aims to examine the effects of local corrosion on the axial compression performance of concrete-filled steel tubular (CFST) members. Nineteen CFST short columns with local corrosion were designed and fabricated to undergo axial compression mechanical property tests, with the radial corrosion depth of the local corrosion area as the key test parameter. The failure mechanism and mechanical property change laws of CFST axial compression short columns with circumferential full corrosion at the ends and middle were studied. Combined with finite element modeling, the influence laws of the three-dimensional geometrical characteristics of the local corrosion zone, i.e., the axial length, the annular width and the radial depth, on the structural bearing performance were thoroughly explored and discussed. The results revealed that the main reason for the reduction in load-carrying capacity of circular CFST axial columns due to local corrosion is attributed to the reduction of the effective cross-sectional area of the steel tube in the corrosion area. When local corrosion occurs at different axial positions, the variation range of the bearing capacity of CFST columns is within 10%. Regarding the impact of the three dimensions of local corrosion on the axial load-carrying capacity of CFST, the radial corrosion depth was identified as the most influential factor, followed by the annular corrosion width, and finally by the axial corrosion length. When the axial corrosion length exceeds 20% of the specimen length, its further influence on the load-carrying capacity is considered limited. Finally, a practical calculation formula for the bearing capacity of locally corroded CFST columns is proposed. The predicted results of this formula fit well with the test results and can quickly estimate the remaining bearing capacity of the structure by measuring the geometric parameters of the local corrosion area, providing a reference for the assessment and maintenance of CFST structures.

Finite Element Modelling of Circular Concrete-Filled Steel Tubular Columns Under Quasi-Static Axial Compression Loading

This paper presents a modified finite element analysis (FEA) model for predicting the axial compression strength of large-diameter concrete-filled steel tubular (CFST) stub columns, addressing the gap in research that has often focused on smaller diameters. The size effect, which significantly impacts the structural performance of large-diameter CFST columns, is a key focus of this study. The goal is to validate the accuracy and reliability of the modified FEA model by comparing its predictions with experimental data from the literature, specifically examining ultimate axial load capacity, failure modes, and deformed shapes. In addition to validating the model, this study includes a comprehensive parametric analysis that explores how critical geometric parameters such as the diameter-to-thickness (D/t) ratio and length-to-diameter (L/D) ratio affect the axial compressive behavior of CFST stub columns. By systematically varying these parameters, the research provides valuable insights into the load-bearing capacity, deformation characteristics, and failure mechanisms of CFST columns. Furthermore, the material properties of the steel tube—particularly its yield strength—and the compressive strength of the concrete core are investigated to optimize the design and safety performance of these columns. The results indicate that the FEA model shows excellent agreement with experimental results, accurately predicting the axial load-strain response. It was observed that as the diameter of the steel tube increases, the peak stress, peak strain, strength index, and ductility index tend to decrease, underscoring the size effect. Conversely, an increase in the yield strength and thickness of the steel tube enhances the ultimate strength of the CFST columns. These findings demonstrate the reliability of the modified FEA model in predicting the behavior of large-diameter CFST columns, offering a useful tool for optimizing designs and improving safety margins in structural applications.

Influence of Compressive Strength and Steel-Tube Thickness on Axial Compression Performance of Ultra-High-Performance Concrete-Filled Stainless-Steel Tube Columns Containing Coarse Aggregates

With the increasing use of concrete-filled steel tubular (CFST) structures, exposed steel tubes are highly susceptible to corrosion, posing potential safety hazards. This study innovatively proposes the use of stainless-steel tubes instead of traditional carbon-steel ones and introduces coarse aggregates into ultra-high-performance concrete (UHPC), forming a coarse aggregate-incorporated ultra-high-performance concrete-filled stainless-steel tube (CA-UFSST). The inclusion of coarse aggregates not only compensates for the shortcomings of UHPC but also enhances the overall mechanical performance of the composite structure. Twenty sets of specimens were designed to analyze the influence of four parameters, including the coarse aggregate content, compressive strength, stainless-steel-tube thickness, and stainless-steel type on the axial compression performance of UHPC. The experimental results indicate that the failure mode of UHPC is related to the confinement ratio. As the confinement ratio increases, the failure mode transitions from shear failure to bulging failure. The addition of coarse aggregates enhances the stiffness of the specimens. Furthermore, this paper discusses the applicability of six current codes in predicting the bearing capacity of CA-UFSST and finds that the European code exhibits the best prediction performance. However, as the confinement ratio increases, the prediction accuracy becomes notably insufficient. Therefore, it is necessary to establish a more accurate calculation model for the axial compression bearing capacity.

Seismic performance on PSPC beam – Concrete encased CFST column frame with a built-in reduced beam section

The concrete-filled steel tubular (CFST) column is widely used to connect with a steel beam owing to the quick dry connection and acceptable seismic performance. Therefore, a partially steel-reinforced precast concrete (PSPC) beam with an embedded H-beam was developed to combine the merits of both the prefabrication in the precast concrete beam and the quick assembly in the steel beam. In this study, the developed beam was proposed to connect the concrete encased CFST column with a reduced beam section. A half-scaled frame substructure specimen with two floors and two bays was designed and tested under the cyclic loading to investigate the seismic performance. A series of seismic properties were analyzed, including the failure phenomena, hysteretic performance, stiffness degradation, and energy dissipation capacity. The dog-bone configuration was found to benefit the beam hinge failure mechanism and an acceptable deformation capacity (the ductility coefficient up to 2.77). The function of the H-beam contributed to stable energy absorption (the equivalent damping coefficient from 0.33 to 0.37). Finally, the proposed frame was compared with a reinforced concrete frame and a steel-reinforced concrete frame through numerical analysis. The partial steel-reinforced configuration had a positive influence on the bearing capacity, hysteretic performance, and safety storage. In addition, it could improve the cost-effectiveness with little decrease in the bearing capacity.

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.

Experimental study on infrared detection of debonding in concrete-filled steel tubular structure under acceleratory period of hydration heat action

Concrete-filled steel tubular (CFST) Structures often face challenges with debonding during construction, which can markedly compromise the structural integrity. The hydration of concrete can generate significant heat during construction, making the infrared thermography as a potential method for the defect detection. However, effects of concrete hydration behavior, debonding size, and environmental factors on the infrared thermal imaging of CFST debonding remains unclear. This study conducted experiments using four different hydration heating rates and three debonding sizes to simulate debonding detection using infrared imaging during the hydration phase of CFST. The feasibility of the simulation approach was validated through pair-to-pair comparison, and multiple linear regression analysis was employed to evaluate the impact of these factors. The findings highlight that absolute temperature difference has the most significant impact on detection effectiveness regardless of interaction effects. In regression models without interaction, heating rate demonstrated the least impact, Whereas the model considering the interaction showed that the interaction effect of heating rate and debonding size showed a secondary effect. Further examination indicated that interaction effects decrease as heating rate and debonding size decrease.

Axial compressive behaviour and design of concrete-filled wire arc additively manufactured steel tubes

The axial compressive behaviour of concrete-filled wire arc additively manufactured (WAAM) steel tubular columns is investigated experimentally in this paper. Firstly, the manufacture of a series of WAAM steel plates and tubes is described. The results of tensile testing performed on coupons cut from the WAAM plates, to obtain the mechanical properties of the printed material, are summarised. 3D laser scanning was employed to generate digital models and to capture the geometric features of the WAAM steel test specimens. Concrete was then cast into the WAAM steel tubes, creating a total of nine concrete-filled steel tubular (CFST) specimens of different diameters, thicknesses and lengths that were subjected to compressive loading. The axial compressive load-deformation responses and ultimate loads of the specimens were obtained and the influence of the as-built surface undulations of the WAAM sections was assessed. Comparisons of the test results against existing structural design provisions highlight the need to consider the influence of the weakening effect of the geometric undulations that are inherent to the WAAM process on the structural response of CFST sections, in order to achieve safe-sided strength predictions.

Comparative Study of Life-Cycle Environmental and Cost Performance of Aluminium Alloy–Concrete Composite Columns

As is widely known, the construction industry is one of the sectors with a large contribution to global carbon emissions. Despite numerous efforts in the construction industry to develop low-carbon materials, there is a limited number of studies quantifying and presenting the overall environmental impact when these materials are applied in a construction project as structural members. To address this gap, this study focuses on assessing the life-cycle performance of novel structural aluminium alloy–concrete composite columns. In this paper, the environmental impacts and economic aspects of a concrete-filled aluminium alloy tubular (CFAT) column and a concrete-filled double-skin aluminium alloy tubular (CFDSAT) column were assessed using life-cycle assessment (LCA) and life-cycle cost analysis (LCCA) approaches, respectively. The cradle-to-grave system boundary is considered for these analyses to cover the entire life-cycle. A concrete-filled steel tubular (CFST) column is also assessed for reference. All columns are designed to have the same load-carrying capacity and, thus, are compared on a level-playing basis. A comparison is also made of the self-weight of these columns. In particular, the self-weight of the CFST column is reduced by around 17% when the steel tube is replaced by an aluminium alloy tube, and decreased by 47% when the double-skin technique is adopted in CFDSAT columns. The LCA results indicate that the CO2 emission of CFST and CFAT is almost the same, which is 21% less than the CFDSAT columns due to the use of high aluminium in the latter. The LCCA results show that the total life-cycle cost of CFAT and CFDSAT columns is around 29% and 14% lower, respectively, than that of the CFST column. Finally, a sensitivity analysis was carried out to evaluate the effects of data and assumptions on the life-cycle performance of the examined columns.

Modified plastic stress distribution method incorporating size effect for strength prediction of CFST members

Large-size concrete-filled steel tubular (CFST) members are widely applied in long-span and heavily-loaded structures due to increasing engineering demands. However, due to the size effect, applying the existing design methods to large-size CFST members may overestimate the load capacity, leading to unsafe designs. The plastic stress distribution (PSD) method is widely used as the primary method in typical design codes for calculating the strength of CFST members that are not susceptible to local buckling, while the PSD method was mainly used previously to evaluate the strength of CFST members with relatively small size. In this work, the experimental database of short CFST members with compact sections was complied, and the applicability of the PSD method was evaluated. The results showed that the test-to-calculated ratios decreased with increasing size of CFST members, and unsafe designs emerged for large-size CFST members. Based on the observations, the mechanics-based modified plastic stress distribution (MPSD) method was proposed, which not only considered the size effect at the material level similar to the way treated in most of the previous calculation methods, but also incorporated the size effect of the interaction action between the steel tube and concrete at the member level. Finally, the MPSD method was evaluated against the experimental database, and good agreement was achieved. These results provide strong justification for changes to the PSD method in design standards.

Experimental and numerical investigation on vertical temperature gradient of concrete-filled steel tubular arch under sunlight

To investigate the effects of diameter and inclination on the vertical temperature gradient (VTG) of concrete-filled steel tubular (CFST) arches, this study conducted temperature field tests on three CFST segment specimens with diameters of 426 mm, 750 mm, and 1000 mm, as well as an arch specimen with inclination angles varying from 48.76° to −48.76°. 2D and 3D numerical simulation models were developed to analyze the impact of diameter, wall thickness, inclination and orientation. The results indicate that as the diameter increases, the internal temperature becomes more uniform, forming a constant temperature zone in the middle of the VTG, with linear increases in temperature differences at the top (T1) and bottom (T2). Beyond approximately 600 mm in diameter, the VTG stabilizes. The maximum T1 of the three segment specimens were 15.37 ℃, 22.40 ℃, and 23.81 ℃, respectively. Inclination affects the solar incidence angle and intensity, causing T1 to vary along the arch span, proportional to solar intensity. The maximum difference of T1 in the arch specimen reached 10.87 ℃. Wall thickness showed minimal effect on the VTG. The proposed VTG pattern was applicable to arches with various orientations and can assist in evaluating thermal effects in CFST arches.