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This paper presents an experimental study on the behavior of low-strength concrete columns confined with cold-formed steel under axial compression. The laboratory test specimens consist of four groups of rectangular concrete stub columns in the size of 130 × 200 mm cross section and 300 mm height; the first group composes of the unconfined specimens, while the other three contain the confined specimens under 0%, 25% and 50% sustained axial loads. The jackets are made of two G450-grade channel cold-formed steel sections of 2.4 mm thickness welded together. No bonding material is used between the core concrete and the steel jacket. From the results, it is found that the cold-formed steel jacketing can increase the axial strengths of the unconfined concrete specimens by approximately 40-65%. The strength increase comes mainly from the confinement action, as only small axial deformation is detected in the jacket. Based on the given amount of prescribed preloads in this study, the presence of preload in the column does not have a significant effect on the increase in strength of the confined concrete columns. The measured strength enhancement ratio and the confinement ratio of the tested specimens are compared using five existing strength predictive equations. The performance of the unbonded cold-formed steel jacketing technique adopted in the stub columns is observed to closely conform with the predictive confinement model of the concrete-filled tubes. [ABSTRACT FROM AUTHOR]

Thin-walled composite cylindrical shells are nowadays widely used as primary structures in the aerospace industry. The so-called variable stiffness (VS) composite cylindrical shells with flexible stiffness tailoring characteristics have been made possible by existing AFP techniques. Considering the inherent imperfection sensitivity property of axially compressed thin-walled cylindrical shells, the buckling behaviors of the axially compressed VS composite cylindrical shells with initial geometric imperfections and delamination imperfections are investigated respectively in this paper. The design buckling loads of the axially compressed VS composite cylindrical shells are first determined by the probing method, which is verified by comparing with the existing test data and numerical simulation results. Additionally, a parametric study is conducted to investigate the effects of delamination imperfections on the buckling loads. The constraint delamination sizes of the VS composite cylindrical shells based on the design buckling load in this paper are given. Furthermore, the effects of continuously variable fiber angles on the buckling loads are investigated considering the imperfection sensitivity. The specific VS composite cylindrical shells with both high- buckling loads and low-imperfection sensitivity are obtained. Results indicate that the effects of imperfection sensitivity need to be carefully considered in buckling design of the axially compressed VS composite cylindrical shells. [ABSTRACT FROM AUTHOR]

The research presented in this article consisted of analysis of the ship structural accidents at low temperatures and the effect of carbon percentage in various classifications of carbon steel, compared to the high tensile strength steel materials. The objective of this research was to fill the knowledge gap by expanding the understanding of the influence of low temperature, material, and structure on the axial compression test of tubes. The simulations as idealization of the compression test were conducted with variations in temperature, material carbon percentage, and geometry shape, using Finite Element Analysis (FEA). The results showed that at -100 °C, the material had the best ability to resist compression energy; high carbon steel had the highest strength at various carbon percentages, and the square geometry showed the best ability to absorb energy before failure. [ABSTRACT FROM AUTHOR]

Significant advancements have been made in the area of composite structures. Aligned with an innovative design, the motivation behind this research is, first, to make efficient use of timber as an environmentally friendly material and, second, to employ steel alongside timber effectively to prevent buckling of the steel. This research aims to bridge this knowledge gap by exploring the integration of steel, carbon fiber–reinforced polymer (CFRP), and timber. The objective is to create innovative composite column structures that leverage the unique properties of each material to enhance structural performance and efficiency. The authors conducted tests on a set of 24 columns under compression conditions. The results of the structural tests demonstrated significant compression capacities relative to their mass, highlighting the significant advantages of material synergy within these elements. The study thoroughly quantifies these benefits, shedding light on the potentially transformative impact of these innovative composite columns in the field of structural engineering. A significant finding was the influence of the timber section's geometry on preventing column buckling. Furthermore, the positioning of steel within the sandwich columns played a vital role, with steel elements having a greater area with timber exhibiting enhanced structural performance and reduced likelihood of debonding. This paper introduces a new parameter, the inelastic transition area denoted as INT±70% peak , which characterizes the smoothness or abruptness of the transition once the inelastic region begins and the graph descends. This parameter bears significance in risk analysis for structures susceptible to progressive failure. All specimens displaying substantial energy absorption featured larger timber sections, highlighting the pivotal role of timber in absorbing higher levels of energy during structural loading. The findings contribute to the growing body of knowledge on composite materials and their applications in modern construction. [ABSTRACT FROM AUTHOR]

The purpose of the research was to analyze the experimental-numerical influence of the type of cross-section on the stability of thin-walled composite columns with closed (rectangular) cross-sections. The subject of the investigation was thin-walled composite structures made of CFRP composite (carbon fiber reinforced polimer), characterized by a closed rectangular cross-section shape of the profile and a identical ply configuration. In this study, experimental and numerical investigations of axially compressed columns were performed to determine the values of buckling loads and buckling forms. Experimental investigations were performed using a universal testing machine with an optical deformation measurement system. In parallel with the experimental tests, numerical simulations were made using the FEM (Finite Element Method). The numerical studies conducted using dedicated numerical models and the experimental studies made it possible to carry out a thorough analysis of the impact of the cross-sectional shape on the buckling phenomenon of the structure. The novelty of the present paper is the use of interdisciplinary testing methods to compare the effect of cross-sectional geometry on the stability of thin-walled composite columns.

To further expand the application range of cold-formed steel (CFS) members in practical engineering, a novel fold-fastened multi-cellular steel wall (FMSW) was introduced and investigated in detail. The FMSWs were mechanically connected by the hook-shaped and groove-shaped regions at both ends of the single limb members, by which the assembly efficiency was greatly improved. In this paper, a total of 10 slender FMSW specimens were subjected to axial compressive loadings, and the failure mode, load–vertical displacement curves, load–lateral displacement curves, and bearing capacity of the specimens were obtained. According to the experimental results, the development and failure modes of the local-global interactive buckling of FMSWs were revealed. All specimens experienced local buckling initially, followed by global buckling, and ultimately interactive buckling. The load–displacement curves exhibited similar trends, being characterized by three stages: the elastic stage, the elastic-plastic stage, and the descending stage. Furthermore, the nonlinear ascending segment was short, indicating that the failure was sudden. By comparing the bearing capacities among specimens, it was recognized that the ultimate resistance of FMSWs could be obtained by the superposition of the cells, and the bearing capacity was rarely affected by the height-to-thickness ratio. Based on the experimental results, refined finite element (FE) models were established and the accuracy and effectiveness of the modeling method were verified. Valuable reference could be provided by the research achievements of this paper for the subsequent research of CFS built-up members and their application in practical engineering. [ABSTRACT FROM AUTHOR]

The circular hollow steel-reinforced concrete (HSRC) column consists of an inner circular hollow steel tube and outer circular hollow reinforced concrete (RC). This design provides several advantages, including being lightweight, having a wide sectional profile, and having a high flexural stiffness. This paper aims to investigate the behavior of the circular HSRC columns under axial compression through testing and finite element (FE) modeling. An FE model was established to simulate the circular HSRC columns under axial compression, which was validated against the test data. Additionally, the load distribution and the interface stress between the outer hollow RC and inner steel tube were analyzed. Subsequently, a systematic parametric analysis was conducted on the diameter (d) and thickness (t) of the steel tube; slenderness ratio (λ); strength of concrete (fcu); yield strength of steel tube (fsy), longitudinal rebar (fly), and stirrup (fgy); as well as the stirrup spacing (s). The critical influencing factors of the circular HSRC columns under axial compression were identified. fcu, λ, d, fly, and fsy dramatically influence the bearing capacity, and the stiffness is notably affected by λ and fcu. Finally, three simplified design methods were summarized and evaluated for calculating the bearing capacity of the circular HSRC columns under axial compression. [ABSTRACT FROM AUTHOR]

Laser ablation damage has an important impact on the load-bearing capacity of the aircraft structure. This paper first uses ABAQUS ALE adaptive grid technology to establish and verify the numerical simulation analysis method of laser irradiation ablation of CFRP laminates. Then a finite element simulation analysis was conducted on the buckling process of the CFRP cylindrical shell under the combined loading conditions of laser irradiation and axial compression, and the critical buckling load and buckling mode of the cylindrical shell under different conditions were obtained. The effects of ablation damage and laser irradiation position on the critical buckling load are also discussed. When the laser irradiation position is between the end and the midpoint of the axis in the axial direction of the cylindrical, and is farthest from the axis in the radial direction, buckling failure is prone to occur. [ABSTRACT FROM AUTHOR]

The purpose of the research was to analyze the experimental-numerical influence of the type of cross-section on the stability of thin-walled composite columns with closed (rectangular) cross-sections. The subject of the investigation was thin-walled composite structures made of CFRP composite (carbon fiber reinforced polymer), characterized by a closed rectangular cross-section shape of the profile and a identical ply configuration. In this study, experimental and numerical investigations of axially compressed columns were performed to determine the values of buckling loads and buckling forms. Experimental investigations were performed using a universal testing machine with an optical deformation measurement system. In parallel with the experimental tests, numerical simulations were made using the Finite Element Method (FEM). The numerical studies conducted using dedicated numerical models and the experimental studies made it possible to carry out a thorough analysis of the impact of the cross-sectional shape on the buckling phenomenon of the structure. The novelty of the present paper is the use of interdisciplinary testing methods to compare the effect of cross-sectional geometry on the stability of thin-walled composite columns. [ABSTRACT FROM AUTHOR]

The ductility of FRP-reinforced concrete structures is reduced by the brittleness of FRP bars. To address this issue, this study employs the hybrid reinforcement of stainless steel (SS) and GFRP bars to enhance the ductility of concrete columns. A total of 21 axially compressed seawater and sea sand concrete (SWSSC) circular columns are fabricated, including 15 hybrid GFRP and SS bar-reinforced SWSSC (GFRP-SS-SWSSC) columns, 3 GFRP bar-reinforced SWSSC (GFRP-SWSSC) columns, and 3 SS bar-reinforced SWSSC (SS-SWSSC) columns. The test results are analyzed in terms of failure mode, load–axial displacement curve, bearing capacity, and ductility. Results show that GFRP-SWSSC columns suffer brittle failure, while GFRP-SS-SWSSC columns and SS-SWSSC columns demonstrate ductile failure characteristics. Furthermore, the hybrid reinforcement contributes to an improvement in the bearing capacity of the columns. A calculation equation for the bearing capacity of axially compressed columns was established, providing reasonable predictions of bearing capacities, with a design compressive strain of 2000 με for GFRP bars. It was found that hybrid reinforcement enhanced the ductility of GFRP-SWSSC columns. In addition, when the percentage of the SS reinforcement ratio reaches 50%, the ductility indexes of the GFRP-SS-SWSSC columns closely approach those of the SS-SWSSC columns. [ABSTRACT FROM AUTHOR]

The aim of the current study was to determine the load capacity of composite columns subjected to axial compressive load. The subjects of the study were two types of columns with a rectangular cross-section, with different edge lengths. The tested columns had a closed cross-section. Four different fiber arrangements were analyzed for both cross-sections studied. The research was realized using interdisciplinary methods to determine the mechanism of damage to the composite material, with particular emphasis on damage initiation and propagation. Experimental tests were realized on a testing machine, the analysis was carried out with an acoustic emission system, and image analysis using visual assessment system of deflections of the walls of the structure. In addition, a number of numerical analyses were realized based on advanced modeling techniques for fiber-reinforced composites. A comparative analysis of both quantitative and qualitative results is presented for both analyses. The innovation of the presented research lies in the development of a custom method for modeling structures made of composite material with special emphasis on the failure phase. This will allow to accurately reflect the modeling of thin-walled structures with closed cross-section subjected to loading in a complex stress state. [ABSTRACT FROM AUTHOR]

The spring system functions as a pivotal element of the check valve, with its compression performance significantly influencing the valve's time, flow stability, and other characteristics. Taking cues from conventional springs, a refined rectangular helical spring with integrated support features was thoroughly evaluated for its compression performance. The design approach for this spring was elucidated, encompassing the utilization of the Finite Element Method (FEM) to model its compression behavior. Additionally, a laboratory configuration was implemented to authenticate the findings derived from the FEM simulation. Subsequently, a comparative investigation was carried out between an engineered spring and a conventional spring subjected to analogous processing. The comparative analysis unveiled that the support-featured spring exhibited a diminished lateral offset of 2.84 mm (equivalent to a reduction of 10.1 %) and a force-displacement curve with narrower vibration intervals and smaller amplitudes. Moreover, it exhibited an enhanced force feedback of 17.5 % under identical compression displacement conditions.

The research presented in this article consisted of analysis of the ship structural accidents at low temperatures and the effect of carbon percentage in various classifications of carbon steel, compared to the high tensile strength steel materials. The objective of this research was to fill the knowledge gap by expanding the understanding of the influence of low temperature, material, and structure on the axial compression test of tubes. The simulations as idealization of the compression test were conducted with variations in temperature, material carbon percentage, and geometry shape, using Finite Element Analysis (FEA). The results showed that at -100 °C, the material had the best ability to resist compression energy; high carbon steel had the highest strength at various carbon percentages, and the square geometry showed the best ability to absorb energy before failure.

Self-compacting concrete has the advantages of high fluidity, high uniform density, and low porosity. To promote the engineering application of self-compacting concrete, this article studies the axial compression test of ten square steel tube self-compacting concrete columns. The effects of design parameters such as different grades of concrete strength and internal structures of circular steel tubes, square steel tubes, and H-shaped steel on the mechanical properties of self-compacting fly ash concrete filled square steel tube columns are studied. The failure mode, characteristic load and characteristic displacement, ductility, and energy dissipation capacity of each specimen are analyzed. On the basis of the test, the finite element analysis model of steel tube self-compacting concrete column is established, and the test results and simulation results are compared and analyzed. The results show that: the failure mode of the square steel tube specimen is the multilayer middle and upper ring buckling failure. Internal structural measures of square steel tube and H-shaped steel can improve the bearing capacity, ductility, and energy dissipation capacity of the specimen. It is not recommended to use the specimen with an outer square and an inner circle design. The results of the finite element simulation have a high degree of matching with the test results, which intuitively reflects the changes in force of each component.

The un-plasticized polyvinyl chloride (UPVC) is increasingly used in the construction industry because of its superior properties, particularly in greenhouses with UPVC as the skeleton. This study investigated the bearing capacities of UPVC pipes under axial compression. Eighteen UPVC pipe specimens with length-to-diameter ratios ranging from 24 to 45 were tested under axial compression. The failure modes and buckling resistances of the specimens were analysed. A finite element (FE) model was established to simulate the compressive behaviour of UPVC pipes, and the FE predictions were verified against the experimental results. Subsequently, extensive parametric studies were performed to analyse the effects of the diameter-to-thickness ratio, yield strength, and geometric imperfections on the overall stability of UPVC pipes under axial compression. The experimental and FE results were compared with the buckling curves obtained from the design codes for metallic material columns. Based on the test data and parametric analysis, a formulation of the buckling curves for UPVC pipes was proposed to predict the buckling performance of UPVC pipes better. These findings provide a basis for studying the mechanical performance of UPVC pipes subjected to axial compressive loading.

Concrete filled steel tube columns (CFSTCs) are commonly used in large-span bridges and high-rise buildings. As the shrinkage of concrete may lead to significant degradation in the mechanical performance of CFSTCs, expansive concrete or fibre reinforced concrete is usually employed to improve the mechanical performance of CFSTCs. This study presents an experimental study on the combined effects of expansive agents and steel fibres on the axial compressive behaviour of circular CFSTCs. 13 CFSTCs were designed and manufactured using concrete mixes with varying expansive agent rates and steel fibre contents. The time-dependent expansive behaviours of the specimens were monitored during the concrete curing period. Then, the 13 specimens were tested under axial compression load. The failure modes, compression load-axial strain relationship, hoop strain and axial strain relationship, and ductility were investigated. The results demonstrated that the combined addition of expansive agents and steel fibres would substantially improve the compressive strength and ductile behaviour of CFSTCs.

Hollow hybrid structural tubes were evaluated using commercial-grade Diamond Micro Expanded Mesh (DMEM) thin mesh of aluminum (Al) as structural reinforcement. Axial, transverse (flexural), and radial compression tests were performed on four different layered hybrid structures using bamboo (Bm) and basalt (B). With a maximum force of 34.7 kN, compressive ultimate strength of 238 MPa, and strain of 12.6%, AlBmB (with layers labeled from inside to outside) was the best performer in the axial compression test. AlBmB’s adaptability was demonstrated by the flexural test, showing a maximum bending force of 4.7 kN, a flexural strength of 97.7 MPa, and a decreased deflection of 13.2 mm. Radial compression test results underscored the superior energy absorption characteristics of AlBmB. The varying material interfaces in the hybrid tubes yielded distinctive performances. AlBmB, incorporating bamboo and basalt layers, stood out with superior energy absorption and crush force characteristics, indicating enhanced crashworthiness. The other hybrids AlBm, AlB, and BmB also exhibited commendable performances, emphasizing the adaptability of different material combinations. The meticulous selection of DMEM and innovative roll wrapping method for fabrication reliably influenced the tubes’ mechanical properties. The study contributes to advancing the design of lightweight, durable, and high-strength components.

Axial, flexure, and shear loads are the most common loads that could impact any structure. For instance, wall panels and columns majorly carry axial loads from the beam and slabs; they are also susceptible to flexure and shear loads from the wind or earthquake loads. Insulated concrete form (ICF) is a portable component of interconnected expanded polystyrene (EPS) panels filled with concrete. EPS remains in place and becomes part of the wall to enhance thermal resistance and structural performance. This paper focuses on an experiment that investigated the performance of ICF wall panels under axial compression and flexure. EPS with a higher density of 20 and 40 kg/m3 and a higher thickness of 50 and 100 mm was selected to prepare ICF wall panels for this experimental investigation. In addition, the plain concrete panel was cast for reference. Axial, flexure, and shear load-carrying capacity, load displacement, load–deflection profiles, crack propagation patterns, failure nature, and strain energy are analyzed and reported in this paper. It was observed that ICF panels were superior to plain concrete panels in terms of axial, flexure, and shear load-carrying capacity, failure nature, and absorbed strain energy.

Axial, flexure, and shear loads are the most common loads that could impact any structure. For instance, wall panels and columns majorly carry axial loads from the beam and slabs; they are also susceptible to flexure and shear loads from the wind or earthquake loads. Insulated concrete form (ICF) is a portable component of interconnected expanded polystyrene (EPS) panels filled with concrete. EPS remains in place and becomes part of the wall to enhance thermal resistance and structural performance. This paper focuses on an experiment that investigated the performance of ICF wall panels under axial compression and flexure. EPS with a higher density of 20 and 40 kg/m3 and a higher thickness of 50 and 100 mm was selected to prepare ICF wall panels for this experimental investigation. In addition, the plain concrete panel was cast for reference. Axial, flexure, and shear load-carrying capacity, load displacement, load–deflection profiles, crack propagation patterns, failure nature, and strain energy are analyzed and reported in this paper. It was observed that ICF panels were superior to plain concrete panels in terms of axial, flexure, and shear load-carrying capacity, failure nature, and absorbed strain energy. [ABSTRACT FROM AUTHOR]

An ordinary double steel plate–concrete composite wall (ODSC wall) is composed of core concrete, the faceplates, and shear connectors such as studs, etc. Based on an ODSC wall, a new type of stiffened double steel plate–concrete composite wall (SDSC wall) is conceived by incorporating additional stiffeners and tie plates on the internal surface, which aims to improve the local stability of the faceplates. In the authors' previous study, a series of axial compression tests were conducted on the SDSC walls. The SDSC walls in the test showed better mechanical performance, as the presence of stiffeners changed the buckling deformation mode and significantly improved the corresponding local buckling stress and ultimate strength. In this paper, a comprehensive summary of the prior research on SDSC walls is provided, and the effect of the constructive parameters on the local stability is discussed. The results reveal that the modified formula of the critical stress can degrade to the Euler formula when the stiffener-to-stud spacing ratio (i.e., a/B ratio) approaches infinity. What is more, the analysis model is also applicable for DSC walls with enclosed side plates, and the proposed formula can predict the buckling stress of the SDSC walls with different a/B ratios. In addition, according to the analysis of the numerical simulation, a design approach for SDSC walls to prevent local buckling is provided, which is applicable in practical engineering applications. [ABSTRACT FROM AUTHOR]

A steel tube–reinforced concrete (ST-RC) column is composed of the inner concrete-filled steel tube (CFST) component and peripheral reinforced concrete (RC) component. In this study, the confinement interaction mechanism of axially loaded steel tube–reinforced concrete columns (ST-RC) was evaluated experimentally and analytically. Eleven column specimens were tested, including five ST-RC, three CFST, and three RC columns. The test results found that the confinement interaction between core CFST and outer RC components integrates both advantages while remarkably altering the section equilibrium and confinement mechanism compared with conventional confined concrete. Specifically, the following two aspects need to be considered. First, since the core CFST component is subjected to the secondary confinement provided by outer stirrups, the capacity of an ST-RC column is 1.07–1.21 times greater than that of the simple superposition of CFST and RC components (CFST+RC). Second, for the outer RC component, because the filled-in concrete is confined by the steel tube, the outer stirrups confinement cannot be effectively activated due to the weakened dilation of concrete. Such strain-lagging leads to a steeper falling branch of the load–axial strain curve of the ST-RC column under compression than that of CFST+RC. Finally, based on two modified constitutive models considering the confinement interaction mechanism in the ST-RC column, a well-defined analytical model for predicting the structural performance of axially loaded ST-RC columns was established. [ABSTRACT FROM AUTHOR]

The failure of ultra-high performance concrete (UHPC) under axial compression has significant brittleness, so it is necessary to use fiber reinforced polymer (FRP) to constrain UHPC for achieving ductile failure. This article mainly summarized the research progress of FRP constrained UHPC columns, analyzed the influence of different variables on the compressive performance of FRPconfined UHPC columns and the coupling effect between variables, compared the axial compressive stress-strain models of FRP-confined UHPC columns proposed by previous scholars, and evaluated the existing models using a large amount of collected experimental data. The evaluation results indicated that the existing models provided relatively accurate predictions for ultimate stress, but further improvement and correction are needed for predicting ultimate strain. Based on the data collected in this study, the models had been modified, resulting in improved accuracy in predicting both ultimate stress and ultimate strain. [ABSTRACT FROM AUTHOR]

Rubberised concrete, utilised as infill material within single- or double-skin confinements, has emerged as a sustainable solution, offering improved ductility in structures. Past studies have indicated promising results regarding the axial response of hybrid columns comprising filament wound exterior tubes, rubberised concrete infill, and steel interior tubes. This paper investigates the response of such hybrid columns under eccentric compression using validated numerical techniques. An extensive parametric study is conducted to explore the effects of load eccentricity, rubber percentage, concrete strength, and steel tube strength. Results show that despite credible increases in rubber percentage and load eccentricity, the columns have reasonably good performance. The findings facilitate the prediction of the eccentric behaviour of these hybrid columns across varying rubber percentages, confirming its viability for practical applications under realistic eccentric load conditions. The results further affirm the suitability of this hybrid column in scenarios that necessitate higher ductility. [ABSTRACT FROM AUTHOR]

Waste tires pose an environmental issue that causes health problems when discarded by either land burial or burning. The current study investigated the properties and characteristics of different-length hybrid layered columns of Recycled Steel Fibers (RSF) at a fixed ratio (0.6%) of the volume fraction with utilized fixed content (15%) of Crumb Rubber (CR). Nine square column specimens were prepared and tested under axial compression load to reveal the effect of RSF and CR content on hybrid layered reinforcement columns. The results revealed that as the RSF content increased concrete’s properties were enhanced. However, the inclusion of CR at the top layer resulted in performance reduction. Additionally, the layered structure with CR and RSF has higher characteristic properties, including higher load capacity and displacement. Moreover, adding 0.6% RSF to both layers and CR at the top led to a 120% increase in the toughness of the concrete loading capacity. This was followed by a reasonable improvement in displacement and ductility.

The study investigated the load capacity of cross-shaped concrete-filled steel tubular (CFST) columns under axial and eccentric compression using finite element software ABAQUS. It analyzed six specimens with measured data and an additional 26 specimens with varied parameters, including eccentricity, slenderness ratio, section steel ratio and material properties such as concrete strength and steel yield strength.The objective was to understand how these parameters affect the load capacity of cross-shaped CFST columns. The research findings suggest that as eccentricity and slenderness ratio increase, the ultimate capacity decreases. Conversely, it increases with higher steel content, concrete strength and steel yield strength. Moreover, the bearing capacity deteriorates more rapidly with reduced eccentricity and concrete strength, while it demonstrates a nearly linear increase with greater steel content. Additionally, the study found that enhancing the resilience of the channel steel significantly boosts the load-bearing capacity of the column. Based on these findings, practical design equations were developed to determine the maximum bearing capacity of cross-shaped CFST columns under axial and eccentric compression. These equations are grounded in confined concrete theory and demonstrate robust applicability for practical design purposes.

The results of experimental studies of deformation problems in pipeconcrete specimens with small cross sections are provided and analyzed. The stress-strain state of a steel pipe and a pipe filled with concrete is studied and compared. Experimental determination of the dependencies between axial load and deformations of pipe-concrete and steel bars, as well as evaluation of concrete’s and steel pipe’s contribution to the total load-bearing capacity of the composite section are provided. Tests were carried out for short pipe-concrete specimens with the pipe dimensions equal to 60x2, 76x3 and 102x3.5, as well as for hollow steel pipes with the corresponding dimensions. The diagrams of deformation were obtained basing on the experimental results. The deformation of the pipe-concrete element under central compression occurs in proportion to the deformation of a hollow steel element with the same diameter, that made it possible to evaluate the contribution of concrete to the work of the pipe-concrete cross-section, which turned out to be constant at each stage of deformation. A methodology has been proposed that enables to describe analytically the deformability of pipe-concrete elements under axial compression by means of the analytical model based on the experimental data.

Protecting occupants or payloads in crashes and blasts is of utmost importance in both moving and immobile structures. One way of achieving this is by using a sacrificial energy absorber. Composite tubes have been studied as potential energy absorbers due to their ability to fail progressively under axial compression. In this study, the energy absorption capability of these tubes is enhanced by adding hollow glass particles to the matrix. Drop-weight tests are performed on composite tubes, and a digital image correlation (DIC)-based technique is used to capture their load-displacement behaviour. This eliminates the use of electronic data acquisition systems, load cells, and accelerometers. The load-displacement curves of the tubes are obtained from the DIC-based technique and examined to understand their crushing behaviour. Although the mean crush load shows a drop, an increase in crush length is noticed. The specific energy absorbed by the tubes improves with an increase in GMB volume fraction. The addition of 0.1, 0.2, 0.3 and 0.4 vol fractions of GMB results in the specific energy absorption increasing by 6.6%, 14.7%, 24% and 36.6%, respectively, compared to neat glass fibre-epoxy tubes. Visual examination of the tubes and comparison with tubes subject to quasi-static compression is also performed.

Protecting occupants or payloads in crashes and blasts is of utmost importance in both moving and immobile structures. One way of achieving this is by using a sacrificial energy absorber. Composite tubes have been studied as potential energy absorbers due to their ability to fail progressively under axial compression. In this study, the energy absorption capability of these tubes is enhanced by adding hollow glass particles to the matrix. Drop-weight tests are performed on composite tubes, and a digital image correlation (DIC)-based technique is used to capture their load-displacement behaviour. This eliminates the use of electronic data acquisition systems, load cells, and accelerometers. The load-displacement curves of the tubes are obtained from the DIC-based technique and examined to understand their crushing behaviour. Although the mean crush load shows a drop, an increase in crush length is noticed. The specific energy absorbed by the tubes improves with an increase in GMB volume fraction. The addition of 0.1, 0.2, 0.3 and 0.4 vol fractions of GMB results in the specific energy absorption increasing by 6.6%, 14.7%, 24% and 36.6%, respectively, compared to neat glass fibre-epoxy tubes. Visual examination of the tubes and comparison with tubes subject to quasi-static compression is also performed. [ABSTRACT FROM AUTHOR]

The hierarchical structure and microscale dimensions of carbon nanotube yarns (CNTYs) make them great candidates for the development of integrated sensing applications. The change in the electrical resistance of CNTYs due to mechanical strain, known as piezoresistivity, is the principal mechanism in strain sensing using CNTYs. While the axial tensile properties of CNTYs have been studied widely, studies on the axial piezoresistive response of CNTYS under compression have been limited due to the complexities associated with the nature of the experiments involving subjecting a slender fiber to compression loading in its axial direction. In this study, the piezoresistive response of a single CNTY embedded into a polymeric resin (CNTY monofilament composite) was investigated under axial compression. The results suggest that the CNTY exhibits a strong piezoresistive response in the axial direction with sensitivity or gauge factor values in the order of 0.4–0.5 for CNTY monofilament composites. The piezoresistive response of the CNTY monofilament composites under compression was compared to that under tension and it was observed that the sensitivity appears to be slightly lower under compression. The potential change in sensitivity between the freestanding CNTY and the CNTY monofilament composite under compression is still unknown. Knowing the axial piezoresistive response of the CNTYs under both tension and compression will enable their use in sensing applications where the yarn undergoes compression including those in aerospace and marine structures, and civil or energy infrastructure. [ABSTRACT FROM AUTHOR]

The seismic performance of prefabricated reinforced concrete shear walls is a key point in the safety of the whole assembly structure under earthquake actions. In this study, six specimens of reinforced concrete shear walls were assembled with a cast-in-place vertical joint with a straight, L, or convex shape. The specimens were tested using a low cyclic loading test under an axial compression ratio of 0.2 or 0.3. The stress process, failure pattern, and hysteretic curve of each specimen were measured. Combined with a numerical analysis using the finite element method, the variations in the bearing capacity, stiffness degradation, ductility, and energy dissipation capacity of the tested specimens were analyzed. Results showed that all specimens failed in a shear pattern without an obvious failure phenomenon along the vertical joint. The hysteresis curves exhibited an obvious pinch phenomenon and good deformation ability. The seismic behavior decreased in sequence for the shear walls assembled with a cast-in-place vertical joint with a straight, L, or convex shape, while a higher axial compression ratio improved the bearing capacity of the shear walls. The shear wall with an L-shaped vertical joint had similar seismic behavior to that with a straight vertical joint, but the shear wall with a convex vertical joint exhibited a decrease of 8.5% and 10.9% in bearing capacity, 18.2% and 1.2% in ductility, and 13.1% and 20.6% in energy dissipation, respectively, under an axial compression ratio of 0.2 and 0.3. The bearing mechanisms of shear walls with different vertical joints are explained with the numerical analysis of the stress vector maps of concrete and the stress cloud maps of reinforcements at different stress levels. [ABSTRACT FROM AUTHOR]

As a primary load-bearing component, accurately predicting the bearing capacity of concrete-filled rectangular steel tube (CFRST) members is an essential prerequisite for ensuring structural safety. Machine learning methods are employed to model and predict the axial load bearing capacity of CFRST columns. A test database containing 1119 members is established, and the input parameters of the machine learning model are determined using a combination of data preprocessing and correlation analysis. Four machine learning algorithms, namely Lasso, ANN, RF, and XGBoost, are selected to build the prediction models for axial load bearing capacity, and a comparative analysis of their predictive performance is conducted. The feature importance analysis is performed using the SHAP method. The results indicate that the model based on the XGBoost algorithm achieves the highest prediction accuracy. Through comparison with six existing calculation methods in domestic and international codes, the reliability of its predictive performance is verified. [ABSTRACT FROM AUTHOR]

The purpose of this research was the analysis of the stability of compressed thin-walled composite columns with closed rectangular cross-sections, subjected to axial load. The test specimens (made of carbon–epoxy composite) were characterized by different lay-ups of the composite material. Experimental tests were carried out using a universal testing machine and other interdisciplinary testing techniques, such as an optical strain measurement system. Simultaneously with the experimental studies, numerical simulations were carried out using the finite element method. In the case of FEA simulations, original numerical models were derived. In the case of both experimental research and FEM simulations, an in-depth investigation of buckling states was carried out. The measurable effect of the research was to determine both the influence of the cross-sectional shape and the lay-up of the composite layers on the stability of the structure. The novelty of the present paper is the use of interdisciplinary research techniques in order to determine the critical state of compressed thin-walled composite structures with closed sections. An additional novelty is the object of study itself—that is, thin-walled composite columns with closed sections. [ABSTRACT FROM AUTHOR]

Protecting occupants or payloads in crashes and blasts is of utmost importance in both moving and immobile structures. One way of achieving this is by using a sacrificial energy absorber. Composite tubes have been studied as potential energy absorbers due to their ability to fail progressively under axial compression. In this study, the energy absorption capability of these tubes is enhanced by adding hollow glass particles to the matrix. Drop-weight tests are performed on composite tubes, and a digital image correlation (DIC)-based technique is used to capture their load-displacement behaviour. This eliminates the use of electronic data acquisition systems, load cells, and accelerometers. The load-displacement curves of the tubes are obtained from the DIC-based technique and examined to understand their crushing behaviour. Although the mean crush load shows a drop, an increase in crush length is noticed. The specific energy absorbed by the tubes improves with an increase in GMB volume fraction. The addition of 0.1, 0.2, 0.3 and 0.4 vol fractions of GMB results in the specific energy absorption increasing by 6.6%, 14.7%, 24% and 36.6%, respectively, compared to neat glass fibre-epoxy tubes. Visual examination of the tubes and comparison with tubes subject to quasi-static compression is also performed. [ABSTRACT FROM AUTHOR]

Stainless steel has the characteristics of oxidation resistance, high temperature resistance, corrosion resistance, high strength, and high yield ratio. The use of stainless steel bars can extend the life of a structure, reduce later maintenance costs, and reduce the whole life cycle cost of the structure. In this paper, nine concrete columns reinforced with duplex stainless steel (S2205) (DSSRC) and nine ordinary reinforced concrete columns (ORC) were poured with the diameter of steel bars as the parameter, and axial compression tests were carried out on these eighteen concrete columns. The failure mode of the concrete columns is analyzed, and the compressive performance indexes of the two kinds of concrete columns are compared. The results show that, compared with the ORC, the cracking load of DSSRC is increased by 33%, the ultimate load is increased by 30.7%, and the deformation performance of the DSSRC is also improved significantly. On the basis of the test, the finite element model of DSSRC was established with the help of ABAQUS software, and the obtained failure law was consistent with the test; the experimental value, the calculated value, and the numerical simulation value of the axial compression capacity were in good agreement, which verified the feasibility of the test and provided a theoretical basis for practical engineering applications. [ABSTRACT FROM AUTHOR]

Recycled aggregate concrete (RAC) technology has received a lot of attention as a green environmental protection technology. However, the unsatisfactory mechanical behavior of RAC restricts its application in engineering practice. The structure of basalt fiber-recycled aggregate concrete-filled circular steel tubes (C-BFRACFST) can dually improve the mechanical behavior of RAC. To observe the axial compression behavior of the C-BFRACFST column, seven specimens were designed with recycled aggregate replacement ratio (0%, 50%, 100%), basalt fiber (BF) content (0 kg/m3, 2 kg/m3, 4 kg/m3) and length–diameter (L/D, 5, 8, 11) as variable parameters for axial compression tests. The failure mode, load–displacement/strain curve, axial compression deformation, ultimate bearing capacity, energy dissipation, and ductility of specimens have been analyzed. The derived constitutive relation of core basalt fiber-reinforced recycled aggregate concrete (BFRAC) constrained by the circular steel tube and the 3D finite element model of C-BFRACFST column have been established to simulate the whole process of compression. It is observed that instability or shear failure occurs in specimens under axial compression load. When the recycled aggregate replacement ratio was increased from 50% to 100%, the change in the energy-dissipation capacity of the specimens was not significant but the ultimate bearing capacity and displacement ductility coefficient decreased by 3.45% and 8.91%, respectively. When the BF content was increased from 2 kg/m3 to 4kg/m3, the change in the ultimate bearing capacity of specimens was not significant; the energy-dissipation capacity at the later stage of bearing increased, and the displacement ductility coefficient was noted to increase by 13.34%. When the L/D was increased from 8 to 11, the energy-dissipation capacity of specimens was decreased, and the ultimate bearing capacity and displacement ductility coefficient declined by 1.37% and 43.52%, respectively. The finite element simulation results are in agreement with the test results. [ABSTRACT FROM AUTHOR]

The object of the research is the behavior of axial compressed piles in the foundations on continuous permafrost soils under global warming. There is a degradation of permafrost soils at present. The permafrost layer is vertically divided into two parts: 1) the top, the active layer; 2) the bottom, the frozen mass. The active layer of soil thaws in summer and freezes in winter. Frozen soil behaves as a rock in winter and as a liquid mass on some soil thickness in summer. Accordingly, the surface forces acting on the pile surface in winter time disappear in the entire melted liquid soil layer in summer time. We considered the design of a pile by the condition of the first kind buckling (form) under axial compression. We took into account the conditions when the depth of the base thawing soil increases in the upper part of the pile at the stages of operation (in the summertime of the pile operation). In addition, we considered the calculation of the pile length under the same conditions at a given load on the pile at the stage of its design. To forecast the piles operating time in pile foundations or individual piles during global warming on the Earth, an algorithm for calculating pile length at the design stage is proposed. The paper provides a numerical example of calculating the pile operational life in the solid frozen soil of the foundation in an oil pipeline support.

Cylindrical shell structures are ubiquitous and essential supporting structures in various engineering applications. The aim of this research work is to provide a comprehensive overview of the behavior of cylindrical shell structures under different loading conditions, including external pressure, axial compression, and bending moment. The study found that the behavior of cylindrical shells was affected by their geometry, including diameter, length, thickness, and imperfections. These factors should be carefully considered in the design and analysis of cylindrical shells. Additionally, stiffeners and sandwich structures can be applied to improve the structural performance of cylindrical shells under different loading conditions. The work also highlighted the latest research trends in the field, such as the use of advanced materials, and numerical simulations to improve the understanding and design of cylindrical shell structures. Overall, this study has provided a valuable resource for engineers and researchers working on cylindrical shell structures, helping them to design and analyze the cylindrical shell structures more efficiently and effectively.

The circular hollow steel-reinforced concrete (HSRC) column consists of an inner circular hollow steel tube and outer circular hollow reinforced concrete (RC). This design provides several advantages, including being lightweight, having a wide sectional profile, and having a high flexural stiffness. This paper aims to investigate the behavior of the circular HSRC columns under axial compression through testing and finite element (FE) modeling. An FE model was established to simulate the circular HSRC columns under axial compression, which was validated against the test data. Additionally, the load distribution and the interface stress between the outer hollow RC and inner steel tube were analyzed. Subsequently, a systematic parametric analysis was conducted on the diameter (d) and thickness (t) of the steel tube; slenderness ratio (λ); strength of concrete (fcu); yield strength of steel tube (fsy), longitudinal rebar (fly), and stirrup (fgy); as well as the stirrup spacing (s). The critical influencing factors of the circular HSRC columns under axial compression were identified. fcu, λ, d, fly, and fsy dramatically influence the bearing capacity, and the stiffness is notably affected by λ and fcu. Finally, three simplified design methods were summarized and evaluated for calculating the bearing capacity of the circular HSRC columns under axial compression.

The ductility of FRP-reinforced concrete structures is reduced by the brittleness of FRP bars. To address this issue, this study employs the hybrid reinforcement of stainless steel (SS) and GFRP bars to enhance the ductility of concrete columns. A total of 21 axially compressed seawater and sea sand concrete (SWSSC) circular columns are fabricated, including 15 hybrid GFRP and SS bar-reinforced SWSSC (GFRP-SS-SWSSC) columns, 3 GFRP bar-reinforced SWSSC (GFRP-SWSSC) columns, and 3 SS bar-reinforced SWSSC (SS-SWSSC) columns. The test results are analyzed in terms of failure mode, load–axial displacement curve, bearing capacity, and ductility. Results show that GFRP-SWSSC columns suffer brittle failure, while GFRP-SS-SWSSC columns and SS-SWSSC columns demonstrate ductile failure characteristics. Furthermore, the hybrid reinforcement contributes to an improvement in the bearing capacity of the columns. A calculation equation for the bearing capacity of axially compressed columns was established, providing reasonable predictions of bearing capacities, with a design compressive strain of 2000 με for GFRP bars. It was found that hybrid reinforcement enhanced the ductility of GFRP-SWSSC columns. In addition, when the percentage of the SS reinforcement ratio reaches 50%, the ductility indexes of the GFRP-SS-SWSSC columns closely approach those of the SS-SWSSC columns.

The aim of the current study was to determine the load capacity of composite columns subjected to axial compressive load. The subjects of the study were two types of columns with a rectangular cross-section, with different edge lengths. The tested columns had a closed cross-section. Four different fiber arrangements were analyzed for both cross-sections studied. The research was realized using interdisciplinary methods to determine the mechanism of damage to the composite material, with particular emphasis on damage initiation and propagation. Experimental tests were realized on a testing machine, the analysis was carried out with an acoustic emission system, and image analysis using visual assessment system of deflections of the walls of the structure. In addition, a number of numerical analyses were realized based on advanced modeling techniques for fiber-reinforced composites. A comparative analysis of both quantitative and qualitative results is presented for both analyses. The innovation of the presented research lies in the development of a custom method for modeling structures made of composite material with special emphasis on the failure phase. This will allow to accurately reflect the modeling of thin-walled structures with closed cross-section subjected to loading in a complex stress state.

Axial compressive performances of stiffened composite panel were studied in this manuscript. In experimental study, buckling phenomenon of three specimens appear at 413kN, 403kN and 403kN respectively while catastrophic failure appears at 964kN, 934kN and 970kN respectively. Thus average failure load is 2.35 times average buckling load, which indicate the large postbuckling capacity. Only local buckling appears in skin bay without buckling in stiffeners. Buckling strain and failure strain were proposed by the average value of several typical position strains at buckling and failure moment respectively. Average failure strain is −6483 με, which is 2.75 times buckling strain (-2354 με). The relationship between buckling and failure strain is similar to that of buckling and failure load. Failure modes contain debonding and fracture of stiffeners, the splitting and wrapped skin. In numerical study, finite element model considering the Hashin damage, cohesive element and geometry imperfection were built. Buckling load and failure load by FE results have −1.2% and −3.9% error compared to experimental ones, indicating the FE results have good accuracy. FE results show that debonding initiation is close to the moment of final catastrophic failure, about 92.7% failure load. Moreover, debonding area percentage have an accelerating increase trend with the compressive load increasing.

In the design of engineering structures, concrete is assumed to have homogeneously mechanical properties. However, in reality, the concrete material is usually not uniform with respect to the height of structures because segregation mostly occurs during construction. The higher density is presented at, the lower part of the structure due to a higher proportion of aggregate and vice versa. Moreover, the disparity of creep, shrinkage, hydration heat, and curing method also leads to the difference in the quality of concrete. Therefore, it is necessary to study the responses of a concrete element with various mechanical properties. In this study, the functional elastic modulus of concrete material (FGC) is investigated numerically for its effects on the static responses of the element under axial compression. Conventional Finite Element Method (FEM) and Meshless method are used to model the structure. The reliability of the numerical model is validated by comparing the obtained results with experimental data.

A new type of stay-in-place formwork column (SFC) was proposed. The square prefabricated shell was made of basic magnesium sulfate cement based composite (BMSCC) and reinforced by angle steel frame. The SFC can be formed after ordinary concrete is poured. The optimum mix ratio of BMSCC was obtained by physical and mechanical tests. The axial compression tests were conducted on 5 SFCs and 3 reinforced concrete (RC) contrast columns, to investigate the effects of the amount of angle steel and the batten plate spacing on the axial compression performance of the SFCs. The results show that the axial compression capacity, cracking load and ductility of the SFC are improved compared with the RC column under the same conditions. The bearing capacity increased by about 13 % and the cracking load increased by more than 54 %. The axial compression capacity increases with the increase of the section area of the angle steel and the decrease of the spacing between the batten plates. According to the theoretical analysis and test results, by introducing the reduction coefficient of angle steel strength and the reduction coefficient of cement strength, the calculation expression of axial compression capacity of short column with BMSCC stay-in-place (SIP) formwork reinforced by angle steel was established.

High-strength steel has been produced and utilised in construction practice in recent years. Even though experimental studies and numerical simulations have been carried out on high-strength steel columns, design methods for columns have not been fully considered in national codes. This paper describes the overall buckling resistance of welded H-columns made of high-strength steel plates. Six steel columns with varied cross-sectional dimensions and slendernesses were compressed to failure in the experimental tests. The ultimate load and failure pattern of columns were determined and compared with values calculating per different national codes. Moreover, numerical simulations were also performed for high-strength steel columns, and residual stresses and initial bendings were considered in the model. The numerical model was verified using test data, and then parametric studies were conducted on the effects of height-to-width ratios of H-sections and slendernesses of columns on ultimate load. The numerical results of the buckling coefficient were also compared with design values following different design codes, and recommendations were made for the overall buckling design of high-strength steel H-columns in accordance with experimental results and numerical simulations.

Background: Shell structures, which are generally implemented in several engineering applications, such as rocket fuel tanks, missiles, fusion reactors, and cooling towers, often have feature openings for internal access. These openings may have a significant effect on buckling load. Objective: This paper aims to investigate the nonlinear buckling behaviour of a concave conical shell (CCS) with a circular cutout under axial compression and to express the amount of reduction in the buckling load of the CCS in connection with the position and diameter of the cutout. The similarity approach used in cones are tried to adapt CCSs and it is aimed to express the lower bound knockdown factors in terms of dimensionless geometry parameters." Methods: An experimental test layout is used to collect load-displacement test data of the CCS samples for various cutout positions and diameters. Then a finite element (FE) model validated with the experimental test data is constructed to reveal the influence of the cutout size, location, and meridional curvature on the load carrying capacity for an extended range of the shell geometry parameters. Results: The presence of cutouts leads to a reduction in the limit load, not much higher than 30%. The results indicate that buckling is mostly triggered at the cutout edges due to uneven stress distribution. Presence of a cutout at the lower part of the CCS is more critical and plays a significant role in the onset of buckling. Conclusion: An empirical equation is proposed for the lower bound knockdown factors, which predicts the maximum reduction in the load carrying capacity quite well. [ABSTRACT FROM AUTHOR]

Experiment was carried out to investigate the influence of quench rate on the axial compression property of AA6060 two-chamber extrusion profile by comparing the compressed-air quench and water quench. It reveals that the higher quench rate is required for the axial compression in contrast to the axial tension. And the crack sensitivity during the compression deformation has no single correlation to the tensile properties. The optical microscopy and transmission electron microscopy studies were conducted to correlate the microstructure and fracture characteristics. It indicates that the primary cracks are both present in the valley of tensile surface and inside the tensile area. The primary cracks on the surface are because of the strain localization, and the intermetallic particles (AlFeSi) initiated the micro-cracks inside the tensile area. Intergranular primary crack is favored when AlFeSi particles, grain boundary misorientation and intense slip band work together. The comparison of two quench conditions shows low quench rate results in high rate grain precipitates and high sensitivity to crack during the compression and bend. It attributes to cohesive bonds weakening between the grains when a large amount of precipitates occur on the grain boundary. Intergranular ductile fracture mechanism is unlikely present in water quench materials because of the low matrix strength combined with the weak population of grain boundary particles. [ABSTRACT FROM AUTHOR]

In this study, experimental research, a numerical simulation, and a theoretical analysis were performed on the bearing capacity of an aluminum alloy circular tube filled with a lightweight filler (ATLF). Bearing capacity tests were conducted for six ATLF columns and two aluminum alloy hollow tubes (AAHTs), and their local buckling failure modes and mechanical properties were obtained. A finite element model was developed using ABAQUS software (ABAQUS 2016, ABAQUS Inc., Palo Alto, CA, USA) for numerical calculations. Furthermore, a large-scale numerical analysis was performed to investigate the effect of structural parameters, such as the tube thickness, diameter, column length, and initial geometric imperfections, as well as the aluminum alloy's properties and the lightweight filler's properties, on the bearing capacity of the ATLF columns and AAHTs under axial compression. Based on the test and numerical analysis results, a formula for calculating the local buckling stress of AAHTs under axial compression is proposed. An improved coefficient of bearing capacity for the ATLF columns caused by the internal lightweight filler was obtained by fitting, and based on the results, a formula for computing the bearing capacity of ATLF columns under axial compression is proposed in this study. [ABSTRACT FROM AUTHOR]

The local buckling of I-section columns is investigated in this paper, where the interaction between the web and flanges is taken into account. An analytical method is first developed based on the classical theory of the elastic buckling of thin plates, with which the main parameters affecting the interaction between the web and flanges are analyzed. The interactive behaviors of the buckling deformations of the I-section with different parameters are then revealed by employing finite element analyses. Simple approximate solutions for the buckling coefficients of the web and flanges are proposed using the energy method, which is capable of providing very accurate predictions compared to the analytical results. Using the simple solutions for buckling coefficients, the limits for the width-to-thickness ratio of I-section columns are proposed. Comparisons between the existing solutions and provisions in design codes indicate that the proposed limits for width-to-thickness ratio are capable of precisely considering the web–flange interaction at the local buckling of I-section columns. [ABSTRACT FROM AUTHOR]

To investigate the toughening effect and stress–strain relationship of steel fibre-reinforced steel slag micropowder ultra-high-performance concrete (UHPC), nine sets of specimens with coarse aggregate and steel fibre contents were prepared for axial compression and elastic modulus tests. This study examines the variations in compressive strength and peak strain of the steel slag micropowder UHPC specimens to determine the corresponding characteristics of the stress–strain relationship. The results indicate that the experimental groups mixed with 1%, 1.5%, and 2% steel fibre increased the peak strain by about 20.3%, 25.3%, and 26.2%, respectively, compared to the non-steel fibre specimens. It can be seen that the toughening effect of UHPC with steel fibre and slag micro powder is good. With a fixed steel fibre content, the compressive strength and peak strain of steel slag micropowder UHPC initially increase and then decrease as the coarse aggregate content increases. The maximum compressive strength is achieved when the steel fibre content is 1.5% and the coarse aggregate content is 20%. A constitutive equation suitable for steel fibre-reinforced steel slag micropowder UHPC was derived through curve fitting based on the experimentally obtained stress–strain curves. The calculated values from the equation show deviations within 10% of the measured values, indicating a good fit. Nonlinear analysis of the entire compression process of prismatic specimens using the finite element method confirms the rationality of the constitutive equation, as the simulated curve closely aligns with the experimental curve. This research findings provide a reference for the engineering application of steel slag micropowder UHPC. [ABSTRACT FROM AUTHOR]

In order to overcome the disadvantage of poor mechanical properties and limited application of rubber concrete, basalt fiber was used to reinforce rubber concrete and prepare a new concrete composite material. The axial compression test and acoustic emission test were performed to verify the advantage of basalt fiber-reinforced rubber concrete in anticracking ability. The purpose of this paper is to further expand the application of rubber concrete in civil engineering, so that waste rubber products could be more sustainable utilization for protecting the ecological environment. The results revealed that as the content of rubber reached 10% and the content of basalt fiber was 4.56 kg/m3 , the toughness of basalt fiber-reinforced rubber concrete increased by more than 25%. The addition of basalt fiber made the shear cracks in rubber concrete change to tensile cracks, which improved the cracking resistance of the concrete. In the failure stage of basalt fiber-reinforced rubber concrete, the energy release rate decreased, and compared with rubber concrete, the proportion of tensile cracks during the cracking process of basalt fiber-reinforced rubber concrete was significantly reduced. [ABSTRACT FROM AUTHOR]