Compressive Behavior Research Articles

Investigating the axial compressive behavior of cruciform CFST columns: An experimental study

Concrete-filled steel tube (CFST) columns enhance seismic resistance, enabling lighter-weight structures with improved fire performance. This study investigates the axial performance of cruciform CFST columns using three half-scale experiments. The cruciform sections were internally configured as unstiffened (UnS-CFST), stiffened (S-CFST), and multicell (M-CFST). Failure mode, stress, displacement, ductility, and strength were evaluated to determine the maximum load-bearing capacity. Compared to UnS-CFST columns, S-CFST and M-CFST exhibited improved ductility and axial compressive performance. The study also looks at how the proposed method for cruciform sections compares to existing design standards for square and circular CFST columns, such as AIJ, EC4, GB 50936–2014, CECS 159:2004, ACI 318R-05, and AS3600–2001. A novel method for determining the maximum load capacity of cruciform CFST columns is proposed, achieving an accuracy of approximately 95 % compared to experimental results. This novel method facilitates the design of cruciform CFST columns.

Analysis of mechanical properties and stress distribution in self-healing microcapsules using micro-compressive test, nanoindentation test, and finite element analysis

Abstract This study analyzed self-healing microcapsules composed of melamine, urea, and formaldehyde (MUF). The thin shell’s mechanical properties were predicted using various techniques to gain a comprehensive understanding of their behavior. The compressive behavior of the microcapsules was assessed through micro-compression testing. The elastic modulus of the thin shell was precisely determined using nanoindentation, a method known for its accuracy in measuring material properties. Finite element analysis (FEA) was then applied, modeling the microcapsule between two plates and treating the core, which contains the healing agent, as an incompressible liquid. The mechanical properties of the thin shell, based on the elastic modulus derived from the nanoindentation test, were incorporated into the FEA, and the results were compared with those from the micro-compression test. Additionally, we analyzed the von Mises stress distribution to evaluate stress concentration within the spherical core–shell structure, ensuring the reliability of our conclusions. The test methods and analysis techniques presented in this study provide guidelines for improving the stiffness of MUF microcapsules. They can be further applied to predict the properties of materials with a spherical core–shell structure.

Tomographic and mechanical study of 3D printed porous polymer structure under compression

This study investigates the influence of open porosity rate and trabeculae diameter on the compressive behavior of structure printed by DLP technology. Three types of structures have been studied : two periodic structures (Cubic and Octet) and one aperiodic structure (Voronoi-based). Each of these structures are printed with a porosity of 40, 60 and 80 % and also with two different trabeculae diameters: 0.45 mm and 0.66 mm. We investigated porosity by micro-tomograpy with ImageJ for the data treatment. We determined the curing time by making a compressive test for different lengths of UV cure. The first results of the study show that Cubic structure has better Young’s Modulus and also better mechanical stress than Octet and Voronoi-based structures.

Compression behavior of square and circular SFRC columns confined with external steel straps

Compression behavior of square and circular SFRC columns confined with external steel straps

Compressive behaviors and deformation mechanism of carbon fiber reinforced epoxy composites: A microscopic and molecular dynamics perspective

AbstractInvestigating the macro‐mechanical properties of polymer composites at the nanoscale is a challenging topic. Here we report the compressive performances of carbon fiber‐reinforced epoxy composites using molecular dynamics (MD) simulations. The evolution of microstructure and microscopic energy, including free volume, radius of gyration, dihedral angle, potential energy, and interaction energy, has been investigated to characterize compressive behaviors at the nanoscale. Molecular chains gradually bend, and the movement space of the molecular chains decreases during compression loading. The radius of gyration and dihedral angle are deformed into a state of irreversible plasticity to accommodate the microstructural transformation. The interaction energy increases and subsequently declines as the carbon fiber/epoxy interface gets closer, reflecting the transition of the internal structure. The inhomogeneity and interfacial concentration distribution of stress, and local molecular stiffness under various strains have been obtained to reveal the nanoscopic mechanism of epoxy failure and interface delamination during compression. This study reveals the compression behaviors and deformation mechanism of carbon fiber‐reinforced epoxy composites at the molecular level, providing directions and possibilities for molecular design and structural optimization of composites.Highlights The nanoscopic compression deformation of CFRP composites is studied. Microstructural evolution and conformation transformation are revealed. The evolution and transition of microscopic energy are analyzed. Micro‐mechanism of epoxy deformation and interface delamination is elucidated.

Ensemble machine learning models for compressive strength and elastic modulus of recycled brick aggregate concrete

This study delivers an in-depth analysis of predicting the compressive strength and elastic modulus of recycled brick aggregate concrete (RBAC). It assembles an extensive database of 633 compression test results and develops five ensemble learning models—random forest (RF), gradient boosting regression trees (GBRT), extreme gradient boosting (XGB), light gradient boosting machine (LGBM) and stacking (St). These models are evaluated against existing empirical formulas with respect to their effectiveness. The findings reveal that machine learning (ML) models outperform existing formulas: for compressive strength prediction, traditional models achieve a maximum determination coefficient R² of 0.38, whereas ML models attain an R² range of 0.91–0.94. For elastic modulus, the highest R² values are 0.44 for traditional models and 0.97 for ML models. Notably, the LGBM and St models excel in predicting compressive strength and elastic modulus, respectively. The study also identifies critical parameters influencing RBAC’s compressive behavior and highlights their impact trends. Remarkably, while the mass-weighted water absorption of coarse aggregates and the replacement ratio of recycled brick aggregates (RBAs) have less impact on compressive strength compared to the effective water-to-cement ratio, they become more influential for elastic modulus. Additionally, the decrease in elastic modulus due to higher RBA replacement ratios or increased mass-weighted water absorption of coarse aggregates exceeds the corresponding reduction in compressive strength. This research not only deepens the understanding of RBAC’s mechanical properties but also provides valuable predictive tools for civil engineering applications.

Investigation on the microstructure and compressive behavior of open-cell copper- Al2O3 composite foams

The objective of this study is to evaluate the mechanical behavior and energy absorption characteristics of open-cell copper- Al2O3 composite foams fabricated using polyurethane foam with an average pore size of 1.2 mm and a combination of electroless and electrodeposition methods. During electroplating process, the composite foams were fabricated with varying amounts of Al2O3 particles (0.1, 0.6, 0.8, and 1 g/l) in electrolyte solution. To assess mechanical properties of the fabricated foams, uniaxial compression test was conducted to determine the maximum compressive strength, energy absorption density, efficiency, and specific energy absorption. The content of Al2O3 in the fabricated composite foams was evaluated using energy dispersive X-ray (EDX) analysis, and the microstructure was examined using scanning electron microscopy (SEM). The results indicate that the incorporation of Al2O3 particles significantly improves the mechanical properties of the copper-Al2O3 composite foam. Specifically, in the composite foam with 9.34 vol% of Al2O3 particles, the maximum compressive strength, total energy absorption, specific energy absorption, and energy absorption efficiency reach 1.03 MPa, 6.48 MJ m−3, 1.9 J g−1, and 75%, respectively. This amount of alumina particles enhances the maximum compressive strength and total energy absorption of open-cell copper foam by approximately 30% and 100%, respectively. However, the mentioned parameters slightly decreased with an increasing amount of Al2O3 particles up to 16.32 vol%. These significant improvements in the mechanical properties of these foams make them well-suited for high-strength applications.

A Study on the Influence of FDM Parameters on the Compressive Behavior of ASA Parts

A Study on the Influence of FDM Parameters on the Compressive Behavior of ASA Parts

Experimental and theoretical study on axial compression behaviour of the modular combined column

Between the modular units of the modular steel building, there exists a combination of the adjacent modular columns. Due to the gaps between the modular columns and the lack of horizontal connections, the integrity of the modular steel structure is weak, which limits the use of modular steel structures in high-rise buildings. This paper proposes a kind of modular combined column realized the connection of modular single columns through the connectors and concrete, which can improve the integrity of the modular steel building. The assembly process of this new modular combined column is described. For axial compressive performance tests, four modular combined column specimens were designed, each with different height or different number of connecting plates. The axial compressive bearing capacity, ductility, stiffness, and other mechanical parameters of the specimens were analyzed according to the phenomena and load-displacement curves of the test. Then, the axial compression failure mode of the modular combined column specimens is compared and analyzed in conjunction with the finite element model. The results indicate that the axial compressive performance and ductility of the combined column suggested in this research are exceptional. The connector can enhance the overall mechanical qualities of the combined column by augmenting the restraining impact of concrete. Finally, the theoretical equation of the axial compression bearing capacity of the modular combined column is obtained by employing the superposition principle, and the equation's reliability is confirmed, along with the test results and the results of the numerical analysis.

Poroelasticity and acoustic properties of bio-based materials : from characterization to the understanding of mechanical dissipation effects

The building sector is a key element in reducing the effects of climate change. To operate sustainably and efficiently, solutions based on building materials having a low environmental impact, such as bio-based materials, are needed. In fact, they present high-level multi-functional properties and they capture atmospheric carbon dioxide. However, even if a number of works has examined visco-thermal dissipation effects, the understanding of the mechanical dissipation effects on the acoustic performances of bio-based materials is still incomplete and little data are available in the literature. Therefore, it seems particularly relevant to investigate by experimental characterizations and modelling methods the effects of mechanical dissipation on the acoustic properties of a representative variety of bio-based materials such as vegetal wools, vegetal aggregate stacks and vegetal concretes. To do this, Young's modulus, Poisson's ratio and structural damping were measured on the various typology of materials by a quasi-static analysis method. The non-linear elastic behaviour in compression of bio-based samples is analyzed. Finally, the influence of Young's modulus and structural damping on the acoustic absorption and attenuation properties of bio-based materials is described using modelling approaches.

In-situ synchrotron high energy X-ray diffraction study on the compressive creep behavior of an extruded Ti-45Al-8Nb-0.2C alloy

Wrought high Nb containing (high Nb-TiAl) alloys are potential materials for low pressure turbine blades in aero-engines. The performance and microstructure evolution under high temperature creep condition is of importance to the service stability of these materials. In this study, the internal strain and FWHM evolution of an extruded TNB-based high Nb-TiAl alloy during compressive creep are characterized by in-situ high energy X-ray diffraction (HEXRD) technique for the first time. The compressive creep test was conducted under a constant load of 300 MPa at 900 °C for 10 h in vacuum. The final creep strain is approximately 1.72 %. The microstructure and phase constitution after creep shows little difference from that before creep. Lattice strain analysis shows that γ phase is plastically deformed while the α2 phase deforms elastically due to the low creep strain. The lattice strain of α2 grains is dependent upon the deformation of surrounding γ grains. Creep induces dynamic recovery, exerting a softening effect. A high number of dislocations are visible in the γ lamellae while almost no dislocations exist within the α2 lamellae. α2 lamellae are partially decomposed and refined via the α2→γ transformation.

Eccentric compression behaviors of iron tailings and recycled aggregate concrete-filled steel tube columns

This paper presents a sustainable method for using iron ore tailings (IOTs) sand and recycled coarse aggregate (RCA) in concrete and concrete-filled steel tube (CFT) columns. The study first examines the impact of RCA replacement ratios (0 %, 50 %, 100 %) on concrete's mechanical properties, finding that both compressive and tensile strengths decrease with higher RCA content due to the negative effects of old interfacial transition zones and adhered cement in RCA. Then, twelve iron tailing and recycled aggregate concrete-filled steel tube (ITRAC-CFT) columns were tested under eccentric compression to assess the effects of varying RCA replacement ratios, eccentricity ratios (0.3, 0.5), and slenderness ratios (12.12, 19.05). Results indicate that RCA ratios have minimal impact on failure modes, ultimate bearing capacity, and stiffness, although ductility increases with higher RCA content. As slenderness ratios increase, the ultimate bearing capacity decreases by 5.3 % and 6.8 % for eccentricities of 0.3 and 0.5, respectively. The study further validates these findings through the finite element method (FEM), showing strong agreement between experimental and predicted results, average value, standard deviation, and coefficient of variation of Nu/NFE were 1.02 %, 0.04, and 3.92 %, respectively. Finally, a comparison with existing design codes (EC4, AISC 360, and GB 50396) reveals that AISC 360 provides the most accurate predictions of the ultimate bearing capacity of ITRAC-CFT columns. The research concludes that the comprehensive use of IOTs sand and RCA in CFT structural concrete is a highly viable and eco-friendly solution, offering potential benefits for sustainable construction practices.

Axial compression stress-strain relationship of lithium slag rubber concrete

Replacing cement with lithium slag and fine aggregate with rubber in concrete solves waste disposal, reduces material consumption, boosts sustainability, and enhances concrete performance. A set of prismatic concrete specimens with varying proportions were designed and experimentally tested in order to study the compressive stress-strain behavior of lithium slag rubber concrete (LSRC). The main factors affecting the specimens were lithium slag substitution ratio (SL=0%, 10%, 20%, 30%) and rubber substitution ratio (SR=0%, 5%, 10%, 15%). The results demonstrated that the LSRC exhibited good integrity during the damage. Furthermore, the incorporation of lithium slag (LS) was found to effectively compensate for the reduction in compressive strength due to the incorporation of rubber. When 10% of the fine aggregate was replaced with rubber and 20% of the cement was substituted with lithium slag, the axial compressive strength, elastic modulus, and peak strain of the tested specimens increased by 21.57%, 6.92%, and 17.26%, respectively. Compared with ordinary concrete, LSRC has good toughness, impact resistance and durability with minimal loss of strength, and has broad application prospects in engineering fields (such as airports, highways, housing expansion joints, concrete floors and railway concrete sleepers, etc.). Based on the experimental data, simplified modified equations to predict the compressive strength, elastic modulus, peak strain and axial stress-strain constitutive model of LSRC were proposed, so as to promote the development of LSRC.

Evaluating the impact of industrial wastes on the compressive strength of concrete using closed-form machine learning algorithms

Industrial wastes have found great use in the built environment due to the role they play in the sustainable infrastructure development especially in green concrete production. In this research investigation, the impact of wastes from the industry on the compressive strength of concrete incorporating fly ash (FA) and silica fume (SF) as additional components alongside traditional concrete mixes has been studied through the application of machine learning (ML). A green concrete database comprising 330 concrete mix data points has been collected and modelled to estimate the unconfined compressive strength behaviour. Considering the concerning environmental ramifications associated with concrete production and its utilization in construction activities, there is a pressing need to perform predictive model exercise. Furthermore, given the prevalent reliance of concrete production professionals on laboratory experiments, it is imperative to propose smart equations aimed at diminishing this dependency. These equations should be applicable for use in the design, construction, and performance assessment of concrete infrastructure, thereby reflecting the multi-objective nature of this research endeavour. It has been proposed by previous research works that the addition of FA and SF in concrete has a reduction impact on the environmental influence indicators due to reduced cement use. The artificial neural network (ANN) and the M5P models were applied in this exercise to predict the compressive strength of FA- and SF-mixed concrete also considering the impact of water reducing agent in the concrete. A sensitivity analysis was also conducted to determine the impact of the concrete components on the strength of the concrete. At the end, closed-form equations were proposed by the ANN and M5P with performance indices which outperformed previous models conducted on the same database size. The result of the sensitivity analysis showed that FA is most impactful of all the studied components thereby emphasizing the importance of adding industrial wastes in concrete production for improved mechanical properties and reduced carbon footprint in the concrete construction activities. Also, the M5P and ANN models with R2 of 0.99 showed a potential for use as decisive models to predict the compressive strength of FA- and SF-mixed concrete.

Enhancing compressive behaviour of seawater sea sand concrete filled hybrid carbon-glass FRP tubes exposed to seawater: Effect of thickness

This study presents a novel investigation into the impact of tube thickness on the residual compressive strength of sea water sea sand concrete (SWSSC) filled filament wound hybrid fibre-reinforced polymer (HFRP) tubes, positioning them as innovative alternatives to traditional concrete-filled steel tubes in corrosive marine environments. The research explores tube thicknesses of 2 mm, 3 mm, and 4 mm, employing a unique hybrid configuration of 50 % carbon fibre reinforced polymer (CFRP) internal layers and 50 % glass fibre reinforced polymer (GFRP) external layers. This study examines the effect of these configurations on compressive mechanical properties, microstructural characteristics, and damage progression under alkaline and seawater conditions. Additionally, the research evaluates cross-ply and hoop orientations as variables in filament winding fibre orientation. A comprehensive set of 108 hybrid tubes were filled with an alkaline solution to simulate the SWSSC environment and exposed to seawater at varying temperatures and durations. Accelerated aging experiments were conducted in the laboratory to assess the long-term compressive performance of SWSSC-filled HFRP tubes exposed to seawater. Long-term compressive strength predictions were made using the Arrhenius theory, based on short-term accelerated aging data. The accelerated test data revealed maximum compressive strength reductions of 33 %, 15 %, and 17 % for 2 mm, 3 mm, and 4 mm cross-ply HFRP tubes, respectively, after 150 days of exposure at 60 °C. For hoop HFRP tubes, the corresponding reductions were 19 %, 18 %, and 17 %. Thicker tubes (3 mm and 4 mm) with sufficient internal CFRP layers protect external GFRP layers from alkaline damage, akin to pure CFRP tubes. Thinner tubes (2 mm) exhibit similar performance to GFRP tubes as alkaline damage spreads from their less substantial internal CFRP layers to the outer GFRP layers. For cross-ply tubes, the recommended strength reduction factors are 0.6 for 2 mm, 0.8 for 3 mm, and 0.8 for 4 mm thicknesses. For hoop tubes, the suggested factors are 0.7 for 2 mm, 0.7 for 3 mm, and 0.8 for 4 mm thicknesses. This study shows the innovative potential of tailored hybrid HFRP tubes in enhancing the durability and performance of marine infrastructure.

Axial compression behaviour of square steel tubes encased by and filled with high-strength recycled aggregate concrete

The axial compression behaviour of square steel tube (SST) columns encased with recycled aggregate concrete (RAC) and filled with RAC (RAC-encased RACFSST) columns was investigated. Using high-strength concrete, five specimens were tested under axial compression until failure. The experimental parameters included the coarse aggregate type, stirrup spacing, wall thickness of the SST and the existence of cross-tie bars in the SST. The failure mode, load–displacement curves, load–strain curves and ductility of the composite columns were obtained. The impacts of the various parameters on the mechanical performance of the RAC-encased RACFSST columns were evaluated. The failure modes of the composite columns were comparable. The inclusion of RAC enhanced the load-bearing capacity (LBC) of the column, but negatively affects its ductility and deformation capacity. Increasing the wall thickness of the SST and reducing the stirrup spacing significantly improved the axial compressive performance of the columns, as mainly reflected in the axial compressive capacity and ductility, respectively. Cross-tie bars inside the SST improved the LBC and deformation capacity. The axial bearing capacities of the columns and those in other studies were determined using existing codes. The computed results were very consistent with the experimental data.

Performance Assessment on the Manufacturing of Zn-22Al-2Cu Alloy Foams Using Barite by Melt Route

A barium-rich Celestine (Sr,Ba)SO4 concentrate from the primary Mexican ore production was used as a thickening agent to produce closed-cell Zn-22Al-2Cu alloy foams, while calcium carbonate was used as a foaming agent. The microstructure and mechanical properties of the foams were analyzed by optical microscopy, scanning electron microscopy, and compression tests, respectively. The Zn-22Al-2Cu alloy foams showed a typical lamellar eutectic microstructure, constituted by a zinc-rich phase (η) and a (α) solid solution that was richer in aluminum, while a copper-rich (ε) phase was formed in the interdendritic regions. The SEM micrographs show the presence of small particles and aggregates that are randomly scattered in the cell walls and correspond to unreacted calcite and Celestine–Barian particles, especially for the higher barite addition. The compressive curves showed smooth behavior, wherein the particles at the cell walls did not affect the foam’s compressive behavior. The trial containing 1.5 wt. % of BaSO4 and 1.0 wt. % of CaCO3 showed a higher energy absorption capacity of 5.64 MJ m−3 because of its highest relative density and lowest porosity values. The Celestine–Barian concentrate could be used as a foaming agent for high melt-point metals or alloys based on the TGA results.

Eccentric compression behavior of CFRP-confined reactive powder concrete-filled steel tube slender columns

Ultra high and large-span structural components are needed in urban modernization construction to meet the engineering requirements. Reactive powder concrete-filled steel tubes (RPCFSTs) provide a cost-effective and efficient solution for optimizing space utilization in super high-rise buildings and enhancing the crossing capacity of bridge, which accords with such development. However, these components have inherent drawbacks in terms of local buckling and corrosion resistance. The use of carbon fiber reinforced polymer (CFRP) confinement to suppress this innate deficiency has been proven to show great advantages in limited trial results. This article establishes a comprehensive test scheme to investigate the eccentric compression performance of CFRP-confined RPCFST columns. A total of 11 specimens were prepared and subjected to biased compression test by varying the component length (400, 800, 1200, and 1600 mm), number of CFRP layers (0–3), and load eccentricity (0, 10, 20, 30, and 40 mm). The results showed that the CFRP confinement could effectively enhance the bearing capacity and energy dissipation capability of RPCFST columns while delaying the local buckling of slender specimens with low slenderness ratios. The improvement of ultimate load due to CFRP confinement exceeded 42.5 %. However, in specimens with higher slenderness ratios and with increasing load eccentricity, the confinement effect of the steel tube on the core RPC tended to weaken. An N–M interaction model for slender CFRP-confined RPCFST columns was established, and this model was validated to be in good agreement with the experimental results. The conclusions drawn from this study might given a solid foundation for the future application of CFRP-confined RPCFST structures.

Finite element analysis for axial compressive behavior of CFT columns assembled with rectangular wave-shaped ribs

This is an analytical study on the axial compression behavior of newly developed Concrete-Filled Steel Tube (CFT) columns assembled with rectangular wave-shaped ribs for thin-walled design. Based on previous experimental results, a Finite Element (FE) method suited for CFT columns was developed. Next, the stress distribution and principal stress of concrete were analyzed, as were the stress distribution and local buckling of steel tubes. Based on the results, a parameter study was conducted and used as basic data for the design model. This CFT column effectively suppresses local buckling compared to conventional CFT columns, ultimately improving the concrete confinement effect. Additionally, the compressive strength of concrete increased due to the improved confinement effect, which differed depending on the rib aspect ratio. Thus, a design model incorporating the rib aspect ratio as an independent variable was proposed. The model was validated through comparison between the experimental results and FE model data and was found to accurately predict the behavior.

Experimental and analytical study on the compressive behavior of PMI foam with different densities and cell sizes under intermediate strain rates

Polymethacrylimide (PMI) foam materials have great potential for applications in the field of protective energy absorption owing to their superior compressive properties. Existing studies on the mechanical behavior of PMI foams are limited, particularly for loading at intermediate strain rates. This paper presents a comprehensive experimental study of PMI foam with four different densities under quasi-static and intermediate strain rate compression (0.001 s−1 to 100 s−1). Each density included three different cell sizes to determine their effects on the compressive performance. Loads parallel and perpendicular to the foam rise direction were considered to investigate the anisotropic behavior. Intermediate strain rate tests were conducted using a high-speed hydraulic servo testing machine, which achieved a stable strain rate while ensuring consistent specimen sizes in both quasi-static and dynamic tests. In all the experiments, the compression process was captured using a high-speed camera and the macroscopic deformation mode and microscopic deformation mechanism were analyzed by combining Digital Image Correlation (DIC) and Scanning Electron Microscopy (SEM). The PMI foam with finer cell sizes exhibited an enhanced compression performance. As the strain rate increased, the strain rate effect became more evident in the high-density specimens and an increase in cell size diminished this effect. A modified analytical model incorporating the cell-size correction term was developed based on Gibson and Ashby's model. The modified model exhibited an average error of 4.9 % in the predicted plateau stress of PMI foam with different cell sizes at the same density.