Axial Compression Research Articles

Quasi-Static Finite Element Analysis and Damage Quantitative Evaluation of Special-Shaped Concrete-Filled Steel Tubular Column Composite Frame Structure

ABSTRACT Based on the elaborate 3D solid finite element (FE) model established by ABAQUS software, a pseudo-static analysis was conducted on a special-shaped concrete-filled steel tubular column composite frame structure. The FE model considers the confinement effect of both the steel tubes and the tensile bars exerting on the core concrete. The results of the numerical analysis concerning failure modes, load-displacement hysteretic curves, load-displacement skeleton curves and stiffness degradation-displacement curves demonstrate a strong correlation with the existing quasi-static test data. Furthermore, an in-depth analysis was conducted on the impact of the axial compression ratio of column on the plastic energy dissipation distribution mechanism. With an axial compression ratio of the column ranging from 0.1 to 0.55, the composite frame structure primarily relies on the energy dissipation of beams, while the columns serve as supplementary support, thereby exemplifying the principle of “strong column-weak beam.” As the axial compression ratio rises to the range of 0.6–0.8, the composite frame structure transitions a “strong beam-weak column” structural system. Combined with the longitudinal compressive strain of the steel tube at the bottom of the column, a quantitative evaluation method for seismic damage is proposed, grounded in indexes of “stiffness damage” and “energy damage.” Then, the threshold values of energy damage and stiffness damage are determined across four distinct levels: “elastic stage in small earthquake,” “elasto-plastic stage in medium earthquake,” “plastic stage in heavy earthquake” and “failure stage.” The proposed method effectively evaluate the damage severity of special-shaped CFT column composite frame structure subjected to seismic events.

The role of loading-induced convection versus diffusion on the transport of small molecules into the intervertebral disc.

Limited nutrient transport is hypothesized to be involved in intervertebral disc (IVD) degeneration. It is widely recognized that the dominant mode of transport of small molecules such as glucose is via diffusion, rather than convection. However, recent findings suggest a role for convection-induced by fast (motion-related) and slow (diurnal) dynamic loading in molecular transport of even such small solutes. The aim of this study was to investigate whether fluid exchange induced by simulated physiological loading (composed of both fast cyclic or slower diurnal loading) can influence the molecular transport of a small molecule through the cartilage endplate (CEP) into the nucleus pulposus (NP) of IVDs. The molecular transport of fluorescein through the CEP and into the NP was studied in a bovine CEP/NP explant model and loading was applied by an axial compression bioreactor. The loaded explants (convection and diffusion) were compared to unloaded explants (diffusion alone). In the initial 24h, there were no differences between loaded and unloaded explants, indicating that convection did not enhance molecular transport of small solutes over diffusion alone. Notably, after 48h which corresponds to two complete diurnal cycles of tissue compression, fluid exudation/imbibing and redistribution, the fluorescein concentration was significantly increased in the top and bottom layer of the explant, when compared to the unloaded explant. Slower diurnal cyclic compression of the IVD might enhance the transport of small molecules into the IVD although it could not be discerned whether this was due to diffusion/convection or a combination.

Quantification of internal disc strain under dynamic loading via high-frequency ultrasound.

Measurement of internal intervertebral disc strain is paramount for understanding the underlying mechanisms of injury and validating computational models. Although advancements in noninvasive imaging and image processing have made it possible to quantify strain, they often rely on visual markers that alter tissue mechanics and are limited to static testing that is not reflective of physiologic loading conditions. The purpose of this study was to integrate high-frequency ultrasound and texture correlation to quantify disc strain during dynamic loading. We acquired ultrasound images of the posterior side of bovine discs in the8 transverse plane throughout 0-0.5mm of assigned axial compression at 0.3-0.5Hz. Internal Green-Lagrangian strains were quantified across time using direct deformation estimation, a texture correlation method. Median principal strain at maximal compression 0.038 ± 0.011 for E1 and -0.042 ± 0.012 for E2. Strain distributions were heterogeneous through the discs, with higher strains noted near the disc endplates. This methodological report shows that high-frequency ultrasound can be a valuable tool for quantification of disc strain under dynamic loading conditions. Further work will be needed to determine if diseased or damaged discs reveal similar strain patterns, opening the possibility of clinical use in patients with disc disease.

Axial Compressive Behavior and Calculation Model for Axial-Compressive-Load-Carrying Capacity of Locally Corroded RC Short Columns

The individual effects of the main reinforcement corrosion and stirrup corrosion on the axial compressive behavior of reinforced concrete (RC) columns were evaluated through axial compression tests on 10 full-scale short columns. The primary experimental parameters were the corrosion location and the corrosion ratio of the steel bar. The electrochemical accelerated corrosion method was applied on nine of the columns, including three columns corroded in the main reinforcement, three columns corroded in the stirrup, and three columns corroded in both the main reinforcement and stirrup. The full-field displacement of the column and strain of concrete were evaluated using a non-contact 3D-DIC (digital image correlation) technique. The results indicated that, with the increase in the main reinforcement corrosion ratio, the width of the longitudinal corrosion crack increased. The transverse corrosion cracks appeared when the stirrup corrosion ratio is larger than 8%, and the increase in stirrup corrosion ratio increased the crack number, but had little effect on the crack width. Compared to the non-corroded RC column, the peak load of specimens with main reinforcement corrosion ratios of 8.02%, 9.01%, and 19.27% decreased by 10.53%, 13.56%, and 19.77%, respectively, and that of the specimens with stirrup corrosion ratios of 7.08%, 12.33%, and 24.36% decreased by 11.59%, 12.07%, and 17.15%, respectively. The axial-compressive-load-carrying capacity of RC columns decreased almost linearly as the corrosion ratio of the main reinforcement increases, while it exhibited an approximately bilinear degradation as the corrosion ratio of the stirrups increases. The stirrup corrosion ratio had less effect on the axial compressive loading capacity of the RC column when it was larger than 7.5%. A model for calculating the axial-compressive-load-carrying capacity of the corroded RC short columns was developed based on the impact mechanisms of the corroded main reinforcement and stirrups on the columns’ axial compressive behavior. The calculated results closely matched the test data, demonstrating that the proposed model can reliably predict the residual load-carrying capacity of corroded columns.

Study on static performance of the steel-concrete joint in a high-speed railway hybrid girder low tower cable-stayed bridge

The steel-concrete joint (SCJ) of mixed beam bridge plays a key role in connecting concrete box girder and steel box girder, but its complex structure makes its mechanical properties unclear. Compared with traditional mixed beam cable-stayed Bridges, mixed beam low tower cable-stayed Bridges show stronger competitiveness. However, there is still a lack of published literature on the study of SCJ of mixed beam low tower cable-stayed Bridges for high-speed railway. In order to study its mechanical properties, a scale model test with similar ratio of 1:5 was carried out under the background of Yongjiang River mega-bridge. The results show that under the action of 5.0 times maximum axial force and maximum negative bending moment, the components of the test model are still in the elastic state, the vertical deformation of the model is continuous and smooth, and the slip between steel and concrete is small, which indicates that the model has good bearing capacity and safety. At the same time, the force transfer mechanism of steel-hybrid section under axial compression is discussed by finite element analysis(FEA). The numerical results show that the rear bearing plate is the main force transfer member of the SCJ, while the front bearing plate transmits a small proportion of axial force. Improving the strength of concrete has limited effect on the transmission path, but can enhance the overall stiffness. The increase of the thickness of the rear pressure plate and the T-rib with variable section mainly affects the force transfer ratio of the rear bearing plate, but has little effect on other force transfer indexes and the overall stiffness. The increase of the stiffness of the shear connectors significantly affects the force transfer proportion and the force transfer uniformity of the bearing plate, but its increase is far more than the change of the force transfer index, and the influence on the overall stiffness of the joint section can be ignored. The results can provide reference for the subsequent research and design of similar structures.

The Computational Design of Corrugated Tube Lattice Structure with Negative Stiffness Property Under Axial Compression Load

Negative stiffness (NS) structures have singular mechanical properties and potential applications in various scenarios. A corrugated tube (CT) and an NS lattice structure (NLS) composed of CTs and connection plates are proposed. The mechanical properties of CT and NLS under axial compression are investigated by experiments and simulations. The deformation modes of CT and NLS are layer-by-layer folding of structural layers. The influences of geometric parameters on the compression performance of CT and NLS have been studied. Through a reasonable design of the thickness of upper and lower conical structures, CT and NLS can exhibit periodic changes in peak and valley forces during the compression process, resulting in significant NS behavior. In addition, the increase of CT’s number does not significantly affect the NS effect, and the load-carrying capacity of NLS increases significantly as the number of CT increases. The energy absorption (EA) and peak force values of NLS-[Formula: see text], NLS and NLS-[Formula: see text] are approximately 16, 9, and 4 times those of CT-3.0-0.6-f0.5, and the EA value of an NLS model is the sum of the EA values of its all CTs. In addition, the effects of geometric parameters on the mechanical properties of NLS are systematically investigated. With reasonable parameter values, NLS exhibits strong NS effect and excellent EA capacity.

Effects of Partially Filled EPS Foam on Compressive Behavior of Aluminum Hexagonal Honeycombs

This study investigates the compressive behavior of aluminum honeycombs partially filled with expanded polystyrene (EPS) foam, emphasizing the effects of filler area fractions and vertex contact locations on energy absorption and crush characteristics. Axial quasi-static compression tests evaluated energy absorption, mean crush force, specific energy absorption, and crush force efficiency. Results revealed that partially filled honeycombs significantly enhance energy absorption and mean crush force compared to their unfilled counterparts. However, higher filler area fractions increased mass, reducing specific energy absorption. Circular fillers exhibited lower energy absorption than hexagonal fillers due to their larger contact radius, which reduces stress concentration. The interaction between cell walls and fillers influenced densification strain, with wall–midpoint vertex contacts increasing peak force by reinforcing walls, while corner contacts reduced peak force but improved crush force efficiency. These findings underscore the potential of optimized, partially filled honeycombs for lightweight, energy-absorbing applications, particularly in automotive engineering.

Seismic Performance of Shaped Steel Reinforced High‐Strength Concrete Walls: Cyclic Loading Test and Analytical Modeling

ABSTRACTThe thickness of the bottom shear walls in tall and super‐tall structures is often designed too large to meet the limit requirements of axial compression ratios, which increases the weight and cost of the structure. To address this issue, high‐strength concrete (HSC) and shaped steel are combined to form composite shear wall members. This paper focuses on seismic performance and analytical hysteresis model of steel reinforced HSC shear walls (SRHCW) under high axial compressive load. Firstly, the reversed cyclic test was conducted to investigate the influence of concrete strength and the steel ratio on the seismic performance of SRHCWs by comparing the failure mechanism, hysteretic curves, stiffness degradation, ductility, energy dissipation, and steel bar strain variation of each specimen. Then, a hysteresis model for SRHCWs was established, and the model can be used for the nonlinear analysis and seismic performance evaluation of SRHCWs. Finally, the accuracy of the proposed hysteresis model was evaluated by the experimental data. The experimental results show that under high axial compression ratio, the interstory drift ratio capacity of SRHCWs can reach 3.03% showing excellent deformation performance. The wall specimens built with different strength concrete and shaped steel ratios exhibited similar strength, deformation, and initial stiffness, indicating that the steel ratio of the wall can be effectively reduced by upgrading the concrete strength of the wall specimens while ensuring its seismic performance. The analytical model can well predict the hysteresis force–deformation curves of SRHCWs under high axial load ratios.

The Strain Response to Intraocular Pressure Increase in the Lamina Cribrosa of Control Subjects and Glaucoma Patients.

The purpose of this study was to measure biomechanical strains in the lamina cribrosa (LC) of living human eyes undergoing intraocular pressure (IOP) increase. Healthy control subjects and patients with glaucoma underwent optical coherence tomographic (OCT) imaging of the LC before and after wearing of swim goggles that increased IOP (57 image pairs, 39 persons). Digital volume correlation was used to measure biomechanical strains in optic nerve head tissue and change in depth of the anterior border of the LC. The mean IOP increase in both glaucoma and control eyes was 7.1 millimeters of mercury (mm Hg) after application of the goggles. Among glaucoma eyes, strains that were significant were: contractile Ezz (average = -0.33%, P = 0.0005), contractile Eθθ (average = -0.23%, P = 0.03), Emax (average = 0.83%, P < 0.0001), and Γmax (average = 0.95%, P < 0.0001), whereas the average anterior LC depth (ALD) decreased by 2.39µm (anterior; P = 0.0002). In glaucoma eyes, shear strain Ezθ was greater with worse mean deviation (MD) and visual function index (P = 0.044 and P = 0.006, respectively, multivariate models). Strain compliance for Erθ, Ezθ, and Eθθ all increased with greater MD worsening prior to imaging (P = 0.04, P = 0.007, and P = 0.03). LC strains were measurable 20 minutes after IOP increase, producing axial compression and greater peripheral strain than centrally. Some strain compliances were greater with worse existing visual field loss or with more progressive past field loss. Biomechanical strains are related to measures of glaucoma damage, supporting the hypothesis that optic nerve head biomechanical responses represent a noninvasive biomarker for glaucoma.

Axial and eccentric compressive behavior of partially encased channel–concrete composite columns with bolted connections in modular buildings

This paper introduces a novel partially encased channel–concrete composite (PECC) column for modular buildings, aiming to eliminate the need for cast-in-place concrete and facilitate rapid assembly. The PECC column consists of two prefabricated modules connected by high-strength bolts. To evaluate the column's viability, six slender specimens—one bare steel column and five composite columns—were tested under axial and eccentric compression. Variables considered included the presence of concrete, the type of transverse connections, bolt spacing, and load eccentricity ratio. The compression performance of the PECC columns was analyzed by examining their failure patterns, load–deformation responses, initial stiffness, compressive capacity, and ductility. Test results revealed that the PECC columns failed due to global buckling, concrete spalling, and crushing. The bolted connections effectively prevented module separation, enabling the PECC columns to exhibit favorable compressive behavior. The reinforced concrete encased in the channel delayed the column's buckling failure, increasing its initial stiffness and compressive capacity by 98% and 198%, respectively. Using perforated steel plates instead of transverse links between the concrete and the channel enhanced the column's initial stiffness by 20% but had little effect on its compressive capacity. Reducing the bolt spacing improved the column's initial stiffness and compression resistance by 50% and 5%, respectively. Additionally, a finite element model for the PECC columns was developed and validated against test results. Finally, simplified formulas derived from Eurocode 4 were proposed to estimate the resistance of PECC columns under axial and eccentric compression.

Mechanical behavior of timber columns reinforced with high-performance bamboo-based composites and self-tapping screws under axial compression

Mechanical behavior of timber columns reinforced with high-performance bamboo-based composites and self-tapping screws under axial compression

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

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

Behavior of FRP-Confined Sand and Cemented Sand under Axial Compression

Behavior of FRP-Confined Sand and Cemented Sand under Axial Compression

Experimental, numerical simulation and design methodology of axial compression performance of combined steel columns for modular buildings

Load-supporting columns of modular buildings are their key load-bearing components, but fewer research studies have been conducted so far. To investigate the effects of initial defects of components, bolt-hole sizes, end stiffness, and component slenderness ratios on the axial compressive performance of load-supporting columns, this paper carries out a full-scale modeling experimental study and parametric finite element analysis. Subsequently, the test and finite element results were compared with the predicted results of the specifications in China (GB 50017-2017), the United States (ANSI/AISC 360-22), and Australia (AS 4100-2020) to assess the appropriateness of the specifications. The results show: It is recommended that small-section high-strength bolts be used to connect the load-supporting columns. When the overall and local defect magnitude meets the accuracy requirements, the magnitude size has little effect on the component bearing capacity. The direction of the overall bending defect has little effect on the initial stiffness and peak load-carrying capacity of the steel tube spandrel column. When the regularized slenderness ratio of the components is less than 0.4, the reduction of the hinged restraint capacity is less than 10% compared with that of the stiffened restraint capacity. The Chinese specification can be used for component design and its predictions are on the conservative side. As the section width-to-thickness ratio becomes larger, the predictions of the U.S. specification change from an accurate prediction to one with too large an error. The Australian specification predictions were all on the unsafe side, but most components had errors of 10% or less. The results of this paper help to promote the development of modular building technology.

Enhancing mortar composite matrices with three-dimensional auxetic truss lattice materials for reinforced concrete structures

Auxetic architected materials have been at the forefront of developing materials with a wide range of negative Poisson’s ratios, tunable stiffness, and high ductility due to their novel deformation under uniaxial compression. Despite that, the adoption of auxetic materials in load-bearing applications has been challenged by the requirement that their bulk modulus is significantly less than that of the fully dense parent material. In this paper, we study whether using the same mechanism that provides a negative Poisson’s ratio can be mimicked in an interpenetrating phase composite to enhance its matrix’s peak strength and mechanical behavior. In this case, a brittle matrix can be enhanced with a small volumetric fraction of an auxetic truss lattice. The auxetic phase behaves as reinforcement, increasing the hydrostatic compression and confinement in the matrix caused by the externally applied load and bridging matrix cracking. Our work is focused on rapidly prototyping composites using a concrete/mortar matrix with 15-5 PH stainless steel auxetic truss lattice reinforcement. The families of re-entrant bowtie and double pyramid truss lattices were manufactured using laser powder bed fusion to study the effects of increasing the confinement pressure when embedded in composite mortar/steel matrices. The results of the experimental program with LPBF-manufactured truss lattices tested under axial compression embedded in mortar composites are presented and discussed. Analytical modeling is used to decompose the effects of stiffness and Poisson’s ratio on the confining pressure generated by the reinforcing phase. Numerical results on a perfectly bonded periodic unit cell of the composite material are illustrated, presenting the auxetic confinement pressures for different characteristic angles of the architectures with a maximum increase in confining pressure of 34.4%. Our findings reveal significant enhancements in ductility and peak strength using the proposed scheme, with gains reaching up to 240% and 165%, respectively, when compared to conventionally confined specimens and a non-rule-of-mixtures behavior in the composite.

Crashworthiness of Multicellular Tubes under Axial Compression Based on Polygonal Origami Folding

Crashworthiness of Multicellular Tubes under Axial Compression Based on Polygonal Origami Folding

Thin-walled double-skin concrete-filled steel-box stub columns with perfobond connections: axial compressive behaviour

Thin-walled double-skin concrete-filled steel tube (CFDST) stub columns with perfobond (PBL) ribs stiffened have broad application prospects in prefabricated modular buildings, bridge pylons and tunnels. To evaluate its application potential in engineering, this paper designed nine thin-walled CFDST box stub columns stiffened with PBL ribs and conducted axial loading tests. The failure modes, load-displacement curves, local buckling response, ultimate bearing capacity and ductility of the specimens are discussed. Test results show that PBL ribs constrain the local buckling of columns. Through analysis, the influence of the slenderness ratio, the hole distance and the hole diameter of the PBL rib on the axial compression behavior of the specimen was clarified. In addition, a finite element model was established and the accuracy of the model was verified through experimental results. Subsequently, extensive parametric studies were conducted to obtain the effects of section hollow ratio, steel ratio of the section, steel strength, and concrete strength on the bearing capacity and ductility of PBL ribs stiffened CFDST box stub columns. Finally, a prediction formula for the bearing capacity of PBL ribs stiffened CFDST box stub columns considering local buckling was proposed.

Strength Analysis of Eccentric Rectangular Hollow Section X-Joints Subjected to Axial Compression in the Brace

Strength Analysis of Eccentric Rectangular Hollow Section X-Joints Subjected to Axial Compression in the Brace

Study on seismic performance of narrow flange special-shaped column with herringbone center support

Abstract To solve the problems of convex beam, column and insufficient lateral stiffness of steel frame in residential buildings, a new type of steel special-shaped column with herringbone center support structure system is proposed by combining narrow flange special-shaped column with herringbone center support. The finite element model was established by ABAQUS to study the influence of parameters such as axial compression ratio and shear span ratio on the seismic performance of the structural system. The results show that the hysteresis curve of the structure is full, the lateral bearing capacity is high, and it has stable and reliable energy dissipation performance and plastic deformation ability. The structure has obvious yield and failure process under the action of horizontal reciprocating load, and the whole structure presents ductile failure. The plastic deformation of the structure is concentrated on the support, and the energy is consumed by the buckling of the herringbone central support, while the other structural members remain elastic. The increase of axial compression ratio will lead to a significant decrease in the horizontal bearing capacity and lateral stiffness of the structure. After the buckling of the brace, the structure also has good ductility. With the increase of shear span ratio, the lateral bearing capacity, lateral stiffness and ductility coefficient of the structure decrease.

Comparative study of failure mechanism of CFRP partially confined normal strength concrete (NSC) and UHPC cylinders under axial compression

Ultra-high performance concrete (UHPC) holds significant potential in marine structures due to its superior compressive strength and enhanced durability in comparison to normal strength concrete (NSC). Carbon fiber-reinforced polymer (CFRP) confinement has been proven to improve these properties further. However, the compressive behavior of CFRP-confined UHPC, especially for partial confinement, presents complexities arising from the intricate interaction mechanism between UHPC and wrapped CFRP strips. To address this issue, the present study conducted axial compression tests accompanied by digital image correlation (DIC) analyses. Failure modes, stress-strain behavior, hoop strain distribution, and cracking evolution of CFRP partially confined NSC/UHPC were elucidated, thereby uncovering the underlying load transfer mechanism between NSC/UHPC and wrapped CFRP strips. Research outcomes show that the enhancement in compressive strength fcc/fco (0.99 ∼ 1.43) and strain εcu/εco (1.51 ∼ 2.59) of CFRP partially confined UHPC is relatively lower than the NSC counterparts (1.28 ∼ 2.98 and 3.82 ∼ 15.14, respectively). Moreover, lower hoop strain efficiency εh,rup/εfrp can be found for CFRP partially confined UHPC compared to NSC (0.61 vs. 0.86). These phenomena were primarily attributed to the localized shear-cracking pattern and low dilation behavior of confined UHPC. Based on the experimental results, the elucidation of the underlying load transfer mechanism between UHPC/NSC and wrapped CFRP strips provides valuable insights into comprehending the compressive behavior of CFRP partially confined UHPC. Finally, the “arching effect” is found to exhibit limited effect on the ultimate condition’s prediction of partially confined UHPC according to the failure mechanism and Li et al.’s model can reliably predict the ultimate conditions among the existing models.