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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]

In this work, the deformation behavior of porous ceramics ZrO2–5.5 wt.% Y2O3 with different morphology of the pore space under axial quasi-static compression is studied by the digital image correlation (DIC) method. Two stages of the deformation behavior of the ceramics have been identified, namely, the controlled accumulation of microcracks and the formation of block structures. It has been found that an increase in the average pore size leads to a decrease in the tensile strength, a decrease in the effective elasticity modulus, and an increase in the ultimate deformation, while the nature of the deformation macrolocalization changes from ordered to chaotic one. It is shown that the rate of accumulation of local deformations in the central part of the deformable sample with a pore size of 68 μm is several times higher than in the sample with a pore size of 29 μm. [ABSTRACT FROM AUTHOR]

Characterized with thin and hollow walls, bamboo has very few connective tissues in the transverse direction, and can be easily divided into thin bamboo strips. It is convenient to weave bamboo strips and wind them into loaded components since bamboo possesses good elasticity, flexibility and flexural ductility,. In this paper, the tensile properties of bamboo strips in parallel to the fiber directions were tested, and the relationship between their properties and the number of layers was analyzed. Circular tubes were manufactured using bamboo veneers by varying the winding angle (the angle between the longitudinal axis and the winding direction) to be tested under compression. Seven groups of tubular specimens were manufactured by varying the winding angle between 0 and 90 degrees with 4 identical specimens in each group. The load-displacement and stress-strain responses of each winding angle were investigated and the relationship between the key mechanical properties of tubular sections and the winding angle was analyzed. Obtained results indicate that with increase in the winding angle, the elastic modulus decreases and the ultimate displacement increases. The ultimate stress reached its maximum at a winding angle of 15°. [ABSTRACT FROM AUTHOR]

Steel Circular Hollow Section (CHS) joints have been extensively utilized in construction. Current research mainly focuses on joints reinforced in unloaded states, reinforcement under load less commonly addressed. This study examines the mechanical behavior of CHS T-joints through an experimental analysis of six specimens, each featuring varying brace-to-chord diameter ratios (β), welded under different load factors. Identified primary failure modes of the joints are local buckling and out-of-plane inclination. Furthermore, a thermo-mechanical coupling finite element model, considering the material addition during the welding process, was developed to investigate the influence of the welding under load. The results indicate that welding under axial load has little effect on the ultimate loading capacity of the CHS T-joints. Notably, welding-induced residual deformation on the chord surpasses that on the brace, particularly when welding passes are proximal to the brace-chord intersection. Residual stress in welds is not significantly affected by the stress in the tubular; only the stiffeners near the welds are affected. Despite some joints exhibiting out-of-plane inclination, the enhancement in ultimate bearing capacity exceeds 24%. [ABSTRACT FROM AUTHOR]

Inspired by origami shape, two origami tubes are obtained through the arrangement of single-origami-cell structures (SOSs). Under quasi-static compression load, the specific energy absorption (SEA) value of same direction origami tube (SOT) is 13.46% higher than that of reverse origami tube (ROT). ROT shows the deformation mode of compression rotation, and SOT is layer by layer crushing. Various two-, three-, and four-layer origami structures are proposed through the combination of origami tubes and connecting plates, and their energy absorption efficiency is significantly higher than that of origami tubes. These origami structures exhibit stable deformation modes, mainly axial compression, torsion, and mixed deformation modes. The deformation mode of origami structures with four ROTs (4R) is similar to Fried Dough Twists. Regarding two-layer structures, origami structures consisting of reverse SOTs (RSOTs) and SOTs have significantly higher SEA values than those composed of ROTs and SOTs as well as ROTs and RSOTs. In addition, the compression performance of two-layer origami structures is significantly better than that of three- and four-layer origami structures. The SEA value of two-layer origami structure with two RSOTs and two SOTs (2RS2S) is higher than that of three-layer origami structure with four A cells (4A) and four-layer origami structure with one C cell and three D cells (1C3D) 68.05% and 64.48%, respectively. In summary, the origami structures show excellent mechanical properties and have broad application potential as energy absorbing structures. [ABSTRACT FROM AUTHOR]

An eco-friendly self-compacting geopolymer concrete made of ground granulated blast furnace slag was used as a confinement material in glass fibre-reinforced polymer columns to test its efficiency relating to load carrying capacity toward axial compression and cyclic lateral loads. Steel reinforcements were incorporated to improve the mechanical performance of the proposed composite specimens. Two significant parameters of the GFRP tubular columns viz., diameter to thickness (D/t ratio) and fibre winding angles were varied to examine their effects through experiments on mechanical, ductility, and rigidity characteristics. Two variations of D/t ratio viz., 30 and 50 and three different variations of fibre orientations viz., 0°, 30°, and 45° were considered for parametric analysis. Irrespective of the parameters considered, all the columns showed a two-segmented axial load-deformation pattern with a gradual increase in load carrying capacity post-yielding stage upon axial compression and closed hysteresis loop upon lateral cyclic loading. Stepping up the D/t ratio from 30 to 50 mm retarded the axial load carrying capacity up to 20% and 50% of that of the lateral load carrying capacity, as well as increasing the ductility of the composite columns. 0° fibre orientation showed significant efficiency of 6.67–46.78% relating to axial and lateral load carrying capacity compared to other orientations. The effect of the difference in 30° and 45° orientations was almost negligible, i.e., less than 10% concerning axial and lateral loading characteristics. [ABSTRACT FROM AUTHOR]

Purpose: The present study has described the axial deformation behaviour of mild steel and 7075 -T651 aluminium against 350 kg drop weight falling from different heights (0.67-4.78 m). Three different cross-sections of the circular (55, 70- and 85-mm diameter) and the square tubes (43.41, 55.19- and 66.97-mm edge length) have been considered to ascertain their effect on the axial compression, deformation mode and energy absorption. In addition, the experiments have been performed on a circular (82 mm diameter) mild steel tubes subjected to 350 kg drop weight impact falling from different heights (0.25-1.76 m). Methods: Numerical simulations have been carried out using ABAQUS/Explicit finite element code. The Johnson-Cook material model has been used to simulate the material behaviour of 7075 -T651 aluminium and mild steel tubes. Besides, numerical simulations have also been carried out for reproducing the experimental findings. Results: The predicted results of axial compression are found to have a deviation from the actual results in the range of 4-10%, showing the accuracy of the numerical approach. For both the metallic tubes, the axial compression of the circular and square tubes has been found to be decreased with an increase in the cross-sectional size of the tube, while the energy absorption has been found to be increased with an increase in the cross-sectional size of the tubes. For a given drop weight impact, the axial compression in square tubes has been found to be higher than the circular tubes of equivalent cross-sections. For both the metallic tubes, the energy absorption in the circular tube has been found to be higher than the square tubes of equivalent cross-sections. In addition, the axial compression in 7075-T651 aluminium tubes has been found to be higher than the mild steel tubes while the energy absorption in mild steel tubes have been found to be higher than the 7075-T651 aluminium tubes. Conclusions: Based on the findings, the mild steel tube has been found to be a better energy absorber than the 7075-T651 aluminium tubes and the circular tube describes higher crashworthiness than the square tube. Besides, the higher cross-sectional area tubes illustrate better energy absorption characteristics. [ABSTRACT FROM AUTHOR]

This paper aims to study the experimental and analytical behaviour of cold-formed steel (CFS) T-joint members with or without external ring stiffeners under combined axial compression and bending. The parameters varied in the study include the type of T-joints (with and without ring stiffeners), spacing of the stiffeners (100 mm and 200 mm from the central axis of the T-Joint), and thickness of the ring stiffeners (4 mm and 6 mm). The load–deflection and load-strain behaviour were studied by measuring the overall deflection of the T-joints and strain using dial gauges and strain indicators, respectively. The load-carrying capacity of the T-joints with external ring stiffeners was compared, and the results of a numerical investigation showed good agreement. An extensive parametric study was carried out for different geometric parameters of the ring stiffener, chord, and brace member using the FE model to obtain the ultimate strength of the stiffened T-joints, and strength was also compared and obtained using the published equation. From the results of this investigation, it was found that the T-joints with external ring stiffeners can resist more strength and deformation when compared to the T-joints without external ring stiffeners. [ABSTRACT FROM AUTHOR]

These days, fiber-reinforced polymers (FRP) are being widely accepted in reinforced concrete structures because of their efficient structural performance and corrosion resistance. Efficient lateral confinement to the FRP-reinforced concrete compressive members is essential for their better performance due to the lower modulus of elasticity of basalt-FRP (BFRP) rebars. The combined usage of BFRP helices as transverse reinforcement in FRP-reinforced concrete members is not well examined in the body of literature currently in publication, especially in a variety of configurations. To better understand different transverse reinforcement configurations in FRP-reinforced concrete compressive members, this study is now underway. A combination of internal and external BFRP ties for dual restraints, an internal BFRP helix, external BFRP ties, and single BFRP ties are some of these designs. The investigation explores several aspects of the manufactured components, including the diameter of the longitudinal reinforcement, the type of material used for the transverse reinforcement, the vertical tie spacing, and various tie arrangements. In addition, a unique theoretical model that considers the contributions of both longitudinal and transverse BFRP rebars is put out to forecast the axial strength of the members that are created. When compared to the other two configurations, the results show that the application of BFRP combined helix-ties transverse reinforcement in FRP-reinforced concrete elements is the most effective in terms of core confinement and axial strength. Members with double BFRP ties and internal BFRP helix, as well as those with external BFRP ties, show enhanced axial strengths by 23% and 7%, respectively, in comparison to members with single BFRP ties. Secondary peaks in the load-deformation curves also show that members' ductility increases when the vertical distance between transverse reinforcement is reduced. The inclusion of FRP rebars in the study accounts for the notable higher accuracy of the proposed theoretical model as compared to earlier models, with only a 4% deviation from experimental results. [ABSTRACT FROM AUTHOR]

Glued-laminated timber (GLT) and cross-laminated timber (CLT) have shown great potential in the field of sustainable structures (i.e., beams, slabs and floors). However, GLT and CLT columns are mostly considered as medium–low grade construction materials with a worse structural integral than timber columns. It is crucial to improve the performance of existing timber members to make the structures more acceptable for engineering applications. This study investigated the axial compressive behavior of GLT and CLT columns confined with fiber-reinforced polymer (FRP) sheets. To compare the mechanical properties of this composite structure, twenty groups of laminated Canadian hemlock column specimens were prepared using different FRP types and layer numbers, and two height dimensions were adopted for those columns to evaluate the scale effect. The failure modes of laminated timber columns were significantly influenced by the confinement of FRP, including timber crushing failures, FRP cracking failures and longitudinal buckling failures. According to the load–displacement curves, the load carrying capacity of FRP-confined laminated timber columns were improved by 6.35–36.19% compared with the unconfined specimens. Moreover, the FRP layers could prolong the plastic post-peak failure process. Inspired by confined concrete structures, three analytical predictive equations were derived for ultimate compressive strength. [ABSTRACT FROM AUTHOR]

The coarse aggregate produced from the construction and demolished waste of masonry structure is called mixed recycled coarse aggregate (MRA), which is mainly composed of concrete recycled coarse aggregate (CRA) and brick recycled coarse aggregate (BRA). The paper presents the results of an experimental and numerical study of concrete composite sandwich panel made with MRA. The composite sandwich panel with MRA (CSPMRA) were tested under axial compression to investigate the influence of concrete mix proportion, thickness of insulation board and added edge frame on the load-displacement curve, load-strain curve, vertical displacement, ultimate bearing capacity and failure mode of CSPMRA. Results of the experimental and finite element analysis (FEA) were compared with the results based on Chinese code, ACI design equation and other empirical equations developed by researchers which might be applicable to predict the ultimate load of sandwich panels. A semi-empirical equation was proposed to better fit the experimental and the FEA results. [ABSTRACT FROM AUTHOR]

In order to investigate the strengthening effect of FRP textile grid reinforced ECC composite (abbreviated: TRE) restrained RC columns, this study conducted experimental and theoretical studies on the axial compression performance of TRE strengthened RC square columns with RC square columns as the research object. The effects of the chamfer radius of the original column, the type of FRP grid and the number of layers of the grid on the axial compression performance of the TRE-strengthened RC square column were considered. The axial compression tests showed that the strengthened layer exhibited excellent crack control, the reinforced column cracked as a whole without breaking when it was damaged, and the strengthened layer adhered well to the core concrete. Compared with unstrengthened specimens, the compressive strength, ductility and deformation capacity of the RC square column under TRE restraint were significantly higher. The increase of chamfer radius of square column makes the TRE restraint effect better. Increasing the number of grid layers can significantly improve the ultimate bearing capacity and ductility of the strengthened specimens. The effects of TRE strengthening methods with different FRP grids differed, with the same number of grid layers, the ultimate bearing capacity of the specimens strengthened with CFRP grid reinforced ECC was higher, and the cracking load of the specimens strengthened with BFRP grid reinforced ECC was higher. A model for calculating the ultimate bearing capacity of the TRE-constrained RC square column was established, and the validity of the model was verified by comparing the results of this test. [ABSTRACT FROM AUTHOR]

Concrete-filled steel tubes have become popular due to their desirable properties, including compressive strength, plasticity, and ease of construction. This study aimed to comprehensively analyze the axial response of short columns made of concrete-filled austenitic stainless steel tubes. The different parameters of these columns were carefully evaluated and compared to principal international design codes. This analysis gained a deeper understanding of the structural behavior of concrete-filled stainless-steel tubes under axial compression. Based on the data obtained from the parametric study, two supervised machine learning models were used to model the compression behavior of these elements, the artificial neural networks model and the random forest model. It was observed that the results obtained through machine learning algorithms provide a significantly more accurate response than the models available in design codes. Additionally, it was observed through the study that the best results were achieved with the artificial neural networks model, with a correlation coefficient of 0.99. The trained machine learning models were implemented into software, allowing the prediction of the behavior of these structures in the range of the data presented in the study. [ABSTRACT FROM AUTHOR]

Concrete-filled steel-tube (CFST) composite columns have been used in many different types of structures due to their high strength, good ductility, and practical construction advantages; however, the disadvantage of their weak anti-corrosion and fire protection capacity also restricts their use in some specialized engineering projects. In this paper, experimental investigations on the axial compression characteristics of square CFST composite columns with fiber reinforcement were conducted. The failure mechanisms, energy dissipation coefficient, load and strain fluctuations of the columns were analyzed. Meanwhile, the bearing capacity was verified by numerical simulation results. The findings demonstrate that fiber reinforced concrete improves the test columns' bearing capacity and deformation capacity; the steel fibers had more influence on load-bearing capacity, with the same steel content and steel tube thickness, the bearing capacity can be increased by 67.55%. Whereas the polyvinyl alcohol fibers had better improvement in ductility. The fiber-reinforced concrete specimens showed oblique shear failure, whereas the ordinary concrete specimens had poor deformation ability and exhibited crushing failure. The load-carrying capacity was more sensitive to changes in the steel content, With the steel content increasing from 1.56 to 3.04%, the carrying capacity increases by 33.69%. [ABSTRACT FROM AUTHOR]

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]

This paper investigates the buckling behavior of three-layered cross-laminated timber (CLT) panels, from both the experimental and analytical standpoints. Two different series of specimens are considered: the homogeneous ones, which are entirely made of beech, and the hybrid ones, whose inner layers are made of Corsican pine. The experimental tests aim to evaluate the failure limit loads of the specimens, when loaded by an increasing compression tip force. The analytical formulation is first obtained for a panel with a generic number of layers and after it is specialized for a three-layered panel. Timber layers are modeled as internally constrained planar Timoshenko beams linked together by adhesive layers, which are modeled as a continuous distribution of normal and tangential elastic springs. A closed-form solution of the buckling problem is obtained. The achieved Eulerian critical load of CLT panels depends on two parameters, which account for (1) the interaction between timber layers (due to the glue tangential stiffness) and (2) the rolling shear stiffness of the inner layer. Three different failure criteria are introduced to estimate the limit load. Finally, the analytical limit loads and the experimental ones are compared. [ABSTRACT FROM AUTHOR]

Bionic structures have been widely utilized in the crashworthiness design of thin-walled structures due to their superior energy absorption capabilities. This study constructed a bionic-shell thin-walled tube (BST) with excellent crashworthiness based on the structural bionic principle using the shell shape cross-section as the prototype. First, the theoretical model of the mean crushing force (MCF) for BST under axial compression was developed. An experiment was conducted and the reliability of the finite element model was verified. Then, the effects of structural parameters, such as the number of ribs, wall thickness, and inner tube diameter on the crashworthiness of the BST were investigated using the finite element method. Finally, to obtain the ideal configuration of structural parameters, the BST was optimized using the response surface method (RSM) with specific energy absorption (SEA) and crushing force efficiency (CFE) as the optimization objectives and peak crushing force (PCF) as the constraint condition. The results showed that the BST with six ribs exhibited the best crashworthiness under the same mass. The optimized BST-6 was found to have better energy absorption performance than the double circular tube (DCT) and the bionic-horsetail thin-walled tube (BHT). Compared with the DCT, the SEA and CFE increased by 35.15 % and 32.23 %, respectively. [ABSTRACT FROM AUTHOR]

Monte Carlo Simulation is implemented to analyze the reliability of the ordinary concrete-filled steel tubular (CFST) and tie bar CFST short columns under axial compression. The influences of different section shape, material types, load combination, load ratio, stirrup ratio and stirrup strength on the reliability indexes are evaluated. The results show: Properly configuring tie bars in ordinary CFST can greatly improve the reliability index of CFST by 20–40%; When using the same material and the same load combination, the reliability index of the circular section is the lowest; for CFST axial compression members with the same section shape, when the ratio of office live load to dead load is equal to 1.0, the higher the steel strength and concrete strength, the greater the reliability index. [ABSTRACT FROM AUTHOR]

Thin cylindrical shell structures are used in many fields such as structural elements in many branches of engineering: cooling towers, nuclear reactors, silos and steel tanks, etc. They are often subject to a large number of imperfections, due to their manufacturing difficulties. On most of these structures, the defects do not always appear in the same place. Thus, it is necessary to quantify the simultaneous influence of this factor on the critical load. In this work we propose to analyze the effect of different positions of these localized axisymmetric initial imperfections on the critical load of elastic cylindrical shells subjected to axial compression. Numerical analysis is used to evaluate the buckling resistance. According to the results of the parametric study of the perfect shell, the choice of the modeling method, the type and the number of elements necessary to be used in the numerical analysis have a significant impact on the quality of these results. [ABSTRACT FROM AUTHOR]

This paper presents an experimental and numerical investigation on the buckling behaviour of corroded cold-formed steel (CFS) channel section columns under axial compression. 7 stub columns and 7 medium long columns were accelerated corrosion by the outdoor periodic spray test. Prior to compression tests, the mass, residual thickness, surface morphology and initial geometric imperfection of the corroded CFS columns were measured. The failure modes, load–strain curves and load–axial displacement curves obtained from axial compression tests were discussed. Based on the corrosion morphology, the non-linear finite element (FE) model for the corroded CFS columns was then developed. Finally, the calculation method for corroded CFS channel section columns was proposed. The results indicated that with the increasing mass loss rate, the irregularity of residual thickness increased rapidly at first, and then increased slowly due to uniform corrosion. The failure mode of the corroded specimens may change from distortional buckling to local buckling as the mass loss rate increased. With the increase in mass loss rate, the buckling critical load, ultimate load, post-buckling strength and axial displacement corresponding to ultimate load decreased. The failure positions of distortional buckling and local buckling were mainly related to the corrosion degree of the flange and web, respectively. The FE results were compared against the experiment results showing a good match in terms of both the ultimate strength and failure modes. [ABSTRACT FROM AUTHOR]

Bamboo is a fast-growing biobased building material with a high strength-to-weight ratio, and the combination of bamboo and wood provides an environmentally friendly alternative for building construction. A new type of laminated bamboo–timber composite column was proposed to improve the compressive performance of timber columns, which was expected to obtain better mechanical performance. Bamboo scrimber and Douglas fir were combined to form laminated bamboo–timber composite columns for the experimental study. Axial compression tests were carried out on 5 groups of 15 composite columns. The failure modes of the composite columns were assessed. The laws of axial displacement, lateral displacement, axial strain, ultimate bearing capacity and stiffness were analyzed. Finally, the bearing capacity of the composite columns was calculated by referring to the design specification for timber structures. The results indicated that the composite columns exhibited three failure characteristics. The ultimate bearing capacity and stiffness of the bamboo–timber composite columns increased with increasing amount of bamboo scrimber. The ultimate load of the bamboo–timber composite columns was increased by 23.0–94.6%, while the stiffness was increased by 9.1–38.4%. In addition, the bearing capacity of composite columns was calculated according to two standards. The experimental values of the bamboo–timber composite columns are in good agreement with the theoretical values, and the errors are within 8%. [ABSTRACT FROM AUTHOR]

Since fibre-reinforced polymer (FRP) and stainless steel (SS) offer advantages of corrosion resistance and hybrid confinement, this study proposed a new type of composite column: sea sand concrete (SSC)-filled SS tubular columns with an inner FRP tube (CFSTFs) to help exploit abundant ocean resources in marine engineering. To study compressive behaviours of these novel members, eight CFSTFs and two SSC-filled SS tubular columns (CFSTs) were tested under axial compression. Their axial load-displacement curves, axial load-strain curves in SS or FRP tubes were obtained, and influences of key test parameters (the existence of glass FRP (GFRP) tubes, steel tube shapes, and GFRP tube thicknesses and diameters) were discussed. Further, specimen failure mechanism was analyzed employing the finite element method using ABAQUS software. Test results confirmed the excellent ductility and load-bearing capacity of CFSTFs. The existence of GFRP tubes inside can postpone SS tube buckling, and the content of inner FRP tubes, particularly increasing diameters, was found to improve compressive behaviours. GFRP contents helped develop the second elastic-plastic stage of the load-displacement curves. Furthermore, the bearing capacity of CFSTFs with a circular cross-section was approximately 26% higher than that with a square cross-section, and this difference narrowed with the increase in GFRP ratios. [ABSTRACT FROM AUTHOR]

The paper focuses on deformation of ZrO2−5.5 wt.% Y2O3 ceramics with porosity of 30 to 50% induced by axial compression measured by the digital image correlation techniques. A comparative analysis is given to time dependences of the averaged localized strain accumulation along compressive and tensile stress axes calculated by digital image correlation in different areas of the fracture surface. It is found that strain and fracture of porous zirconia-based ceramics develop in stages. Time dependences of the averaged localized strain accumulation correlate with the strain hardening exponent obtained from stress-strain curves. Macroscopic strain localization is identified for zirconia. Spatiotemporal distribution of instantaneous localized strain along the loading axis measured for the specimen surface by digital image correlation, correlates with the porous ceramics fracture at a macro-level. [ABSTRACT FROM AUTHOR]

To increase the usage cost-effectiveness of stainless steel in structural members, a bimetallic tube composed of an external thin-walled stainless steel tube and an internal relatively thick-walled carbon steel tube is proposed. Fifteen stub specimens including nine stainless-carbon steel tube confined concrete (SCTCC) stubs and six concrete-filled stainless-carbon steel tubes (CFSCT) were tested and analyzed in detail. The results show that both SCTCC stubs and CFSCT stubs exhibit good mechanical performance and shear failure modes. The axial strength of SCTCC stubs is higher than that of CFSCT stubs. Regarding SCTCC stubs, the exterior stainless-steel tube would yield before the interior carbon-steel one. The parametric analysis shows that the rising in the thickness ratio of stainless steel tube would decrease the axial capacity of SCTCC model, but also cause the decrease in the axial resistance of the model beyond the peak to become more subtle. The predicting method regarding the capacity of SCTCC stub under axial compression is proposed based on the current design standard and test results. [ABSTRACT FROM AUTHOR]

In this paper, numerous experimental tests were carried out to study the behavior of concrete containing glass fibers and confined with glass fiber-reinforced polymer (GFRP). Concrete specimens containing different fiber percentages (0.3 wt.%, 0.6 wt.%, 0.9 wt.% or 1.2 wt.%) and with different strengths of concrete (8.5 MPa, 16 MPa and 25 MPa) and different confinement levels (two, four and six layers of GFRP) were used as research parameters. The samples were tested to failure under pure axial compression. The results imply that the confinement effect with GFRP is relatively higher for concrete samples containing glass fiber (GFCC) with a percentage equal to 0.6 wt.%. The theoretical of stress ratios (fcc/fco) estimated by using existing ultimate strength models are found to be close to the experimental results for high strength of GFCC, but not close to the experimental results for low strength of GFCC. [ABSTRACT FROM AUTHOR]

In this study, the axial compressive performance of recycled concrete-filled corroded steel tubular columns was assessed with different concrete strength grades (C30, C45, C60) and different corrosion degrees (0%, 5%, 10%, 15%, 20%). Axial compression tests on 15 specimens were conducted, and the corresponding load–displacement curves, skeleton curves, stiffness degradation curves, characteristic load, characteristic displacement, failure modes, and the stress–strain distribution in steel tube and concrete specimens were obtained and thoroughly analyzed. The load-bearing capacity of the specimens was calculated by the typical local and international standards. The static calculation model of the specimens was built by the finite element software, and the load-bearing capacity and deformation performance were evaluated and compared with the test results. The results showed that with the increase of corrosion degree under the same load, the specimen deformation and central bulge are more prominent, whereas the load-bearing capacity and stiffness decrease. As the concrete strength increased, the load-bearing capacity of specimens increased significantly. The calculated load-bearing capacity values and the finite element analysis results agree well with the test values. The findings of this research can be used in different engineering applications. [ABSTRACT FROM AUTHOR]

A procedure for an analytical solution of the problem of the nonlinear deformation of composite cylindrical shells with initial surface imperfections in the form of various deflections and imperfections of the fibrous material in the form of imperfect bonding between the matrix and fibers is developed. The effect of these factors on the critical loads and the post-critical state of shells under axial compression is analyzed. [ABSTRACT FROM AUTHOR]

Purpose: Needle injection through the outer annulus fibrosus of the intervertebral disc (IVD) is the most practical approach for delivery of therapeutic agents, which have been shown to potentially leak following needle retraction. The goal of this work was to establish a protocol for quantifying post-injection leakage and test its sensitivity to factors believed to affect needle track geometry. Methods: A through-puncture defect procedure, followed by controlled injection, was performed on bovine caudal IVDs. Sensitivity to needle size was tested by injection of saline into unconstrained discs with either a 30G, 26G, or 21G hypodermic needle. Sensitivity to axial load was tested by repeated injection via a 26G needle with either no constraint, fixed height, or 10% axial compressive strain. Sensitivity to flexion was tested by applying combined 0.2 MPa compression and 15° of flexion following injection of 5% of disc volume. Results: Needle diameter significantly affected maximum volume prior to leakage, ranging from 34.6 ± 31.9 µL when using 21G to 115.6 ± 23.6 µL when using 30G. While all unloaded discs leaked, axial compression decreased the incidence of leakage events by 50–100% depending on load history. Forward flexion resulted in a 22% incidence of leakage. Conclusion: Fluid injected into IVDs is at significant risk of leakage following needle retraction. This risk depends on factors which alter the geometry of the needle track, including needle size, pinching due to axial compression, and stretching as a result of forward flexion. [ABSTRACT FROM AUTHOR]

The brittle behavior of concrete under axial compressive loading has been a persistent issue. This study investigates the effectiveness of a hybrid Basalt-E-glass confinement (B-CSM) in improving the compressive behavior of concrete. The B-CSM confinement demonstrates a considerable improvement in ultimate strength and strain capacity by over 250 and 500%, respectively, making it a favorable solution for enhancing the ductility of concrete structures. Specimens at 18.43 MPa unconfined strength, confined with 3-layer B-CSM, demonstrated a 258% ultimate strength enhancement. For 24.43 MPa specimens, the same confinement resulted in a 207% increase in ultimate strength. Specimens with an initial ultimate strain of 18.43 MPa, when confined with 3-layers, showed a notable 516% increase. Likewise, for 24.43 MPa specimens, the same confinement led to a significant 395% improvement in ultimate strain. The use of B-CSM confinement is also effective in terms of cost compared to synthetic fiber-reinforced polymer jackets, and its availability is widespread. Existing analytical models for fiber-reinforced polymer confinement were evaluated, and it was found that these models could not predict the ultimate strength and strain of B-CSM-confined concrete. Therefore, this study proposes a unique regression-based approach for predicting the various points of the compressive stress vs. strain curve of B-CSM confinement. These points are then used to trace the complete stress vs. strain curve, which matches closely with experimental results. This work contributes to the development of new design recommendations for B-CSM confined concrete structures, which can enhance the performance of concrete structures and potentially reduce construction costs. [ABSTRACT FROM AUTHOR]

To study the properties of various steel-pipe combined columns, ten steel pipe combined columns were designed, including five axial compression specimens and five eccentric compression specimens. The test mainly investigated the influence of the combination of a flange steel pipe and web steel pipe on the combined column, including the overall failure mode, local failure mode, load–displacement curve, bearing capacity, and stability of the flange steel pipe and web steel pipes. The test results showed that the overall and local failure modes of the axial compression specimens with different steel pipe combinations were different. The failure modes of the eccentric compression specimens with different steel pipe combinations were almost identical. Except for the eccentric compression specimen PZH2, none of the other eccentric compression specimens exhibited local buckling. The combination of the flange steel pipes and web steel pipes near the flange steel pipes had an obviously effect on the bearing capacity, while the combination of steel pipes in the middle of the web had a lower effect on the bearing capacity. During the loading process, the flange and web steel pipe did not lose stability, and the weld between the steel pipes of the axial compression specimen and the eccentric compression specimen was not damaged. There was no obvious separation between the unwelded parts of the steel pipes. [ABSTRACT FROM AUTHOR]

To study the behavior of coral aggregate concrete (CAC) column under axial and eccentric compression, the compression behavior of CAC column with different types of steel and initial eccentricity (ei) were tested, and the deformation behavior and ultimate bearing capacity (Nu) were studied. The results showed that as the ei increases, the Nu of CAC column decreases nonlinearly. Besides, the steel corrosion in CAC column is severe, which reduces the steel section and steel strength, and decreases the Nu of CAC column. The durability of CAC structures can be improved by using new organic coated steel. Considering the influence of steel corrosion and interfacial bond deterioration, the calculation models of Nu under axial and eccentric compression were presented. [ABSTRACT FROM AUTHOR]

Bamboo has been widely used as a load-bearing material in construction; however, there are limited studies on the stability of slender original bamboo columns. Based on the experimental investigation of thirty-nine original bamboo columns, parametric analyses were conducted to investigate the influence of the diameter–thickness ratio, cross-sectional area and slenderness ratio on the axial compression behavior of original bamboo columns. The test results indicate that the failure modes of the columns are substantially affected by the slenderness ratio and diameter–thickness ratio. For columns with the same diameter–thickness ratio, the ultimate bearing capacity was negatively correlated with the slenderness ratio, and the highest reduction rate for the load-bearing capacity caused by the slenderness ratio was 44.39%. Under the same slenderness ratio, when the diameter–thickness ratio increased by 18.75%, the ultimate bearing capacity increased by 82.65%. An excessive slenderness ratio may result in local buckling, leading to underutilization of the material strength when failure occurs and substantially reducing the load capacity of bamboo columns. Local buckling can be mitigated by decreasing the slenderness ratio and increasing the diameter–thickness ratio. According to the test results, the model predicting the compressive bearing capacity of the original bamboo column was proposed considering the slenderness ratio and diameter–thickness ratio, and it was indicated that the proposed model can provide satisfactory predictive results. [ABSTRACT FROM AUTHOR]

A Machine Learning (ML) model based on Gaussian regression, using different kernel functions, is introduced in this paper to assess the load-carrying capacity of square concrete-filled steel tubular (CFST) columns. The input data used to develop the prediction model, which consists of 314 datasets including the structural geometrical parameters and the mechanical properties of the materials, was collected from available resources in the literature. The performance of the prediction model has also been validated by comparing with: (i) other ML models such as Artificial neural network, Support vector machine, etc.; and (ii) existing formulations in the literature for predicting load-carrying capacity of square CFST columns (including several codes such as EC4, AISC and ACI). The obtained results showed that the proposed model has outperformed them. The drawbacks of the model have been investigated by studying the influence of the input variables, together with uncertainty analysis providing 68, 95, and 99% prediction confidence intervals. Finally, a user-friendly interface has been developed to facilitate the application of the proposed model, providing the prediction value as well as confidence levels. [ABSTRACT FROM AUTHOR]

Methods of producing hollow and nonhollow cylindrical billet by shaping heterogeneous and ceramic materials under axial pressure, with and without a mandrel, are considered. [ABSTRACT FROM AUTHOR]

A procedure for analytical solution of the problem of the stability and post-buckling behavior of composite cylindrical shells with local deflection under axial compression is developed. The algorithm is developed based on the Timoshenko–Mindlin nonlinear shell theory and Byskov–Hutchinson asymptotic method. The dependence of ultimate loads and equilibrium curves on the mechanical and geometric characteristics of the shells and laminate structure is studied. [ABSTRACT FROM AUTHOR]

The current work presents an experimental procedure to determine the mechanical characteristics of individual biomass particulate materials, including comparatively spherical olive pulp particles and hollow cylindrical hay particles. This study also provides a comparison between the mechanical characteristics of wet and dry olive pulp particles. The strength and elastic properties of olive pulp particles were measured by conducting an uniaxial compression tests. For hay particles, the properties were measured by conducting compression tests in axial and radial directions, and three-point bending tests. The analysis of radial compression tests with hollow cylindrical particles was introduced in this paper, using the theory underlying the analysis of curved beams subjected to bending. The results indicated that small soft olive pulp particles are stronger and stiffer than large particles, and that wet olive pulp particles are weaker and softer than dry particles. [ABSTRACT FROM AUTHOR]

In order to obtain a hybrid tube with better energy absorption performance under both three-point bending and axial compression, multi-objective optimization for energy absorption of carbon fiber-reinforced plastics (CFRP)/aluminum (CFRP/AL) hybrid circular tubes was presented in this paper. Experiments and finite element model (FEM) of the hybrid circular tubes subjected to three-point bending and axial compression were performed, and the finite element models were validated. The effects of fiber filament winding angle (θ) and aluminum wall thickness (t) on energy absorption characteristic of the hybrid tube under three-point bending and axial compressive were discussed by FEM. The results show that θ and t have different effects on the specific energy absorption (SEA) of the hybrid tube under three-point bending and axial compression, respectively. A five-order polynomial response surface (PRS) and artificial neural network (ANN) were used to connect variables (θ and t) and the objective (SEA), respectively. It was found that the fitting accuracy of ANN was better. The non-dominated sorting genetic algorithm-II (NSGAII) was applied to obtain optimal results in the form of Pareto frontier solutions. The specific energy absorption of the optimized hybrid tube (θ = 24°, t = 1.45 mm) verified by simulation under three-point bending and axial compression is 1.11 kN/kg and 45.59 kN/kg, respectively. The hybrid tube exhibits better specific energy absorption under both loads. [ABSTRACT FROM AUTHOR]

An investigation is conducted on the static ultimate limit state assessment of ship hull plates with elastically restrained edges subjected to axial compression. Both material and geometric non-linearities were considered in finite element (FE) analysis. The initial geometric imperfection of the plate was considered, while the residual stress introduced by welding was not considered. The ultimate strength of simply supported ship hull plates compared well with the existing empirical formula to validate the correctness of the applied boundary conditions, initial imperfection and mesh size. The extensive FE calculations on the ultimate strength of ship hull plates with elastically restrained edges are presented. Then a new simple empirical formula for plate ultimate strength is developed, which includes the effect of the rotational restraint stiffness, rotational restraint stiffness, and aspect ratios. By applying the new formula and FE method to ship hull plates in real ships, a good coincidence of the results between these two methods is obtained, which indicates that the new formula can accurately predict the ultimate strength of ship hull plates with elastically restrained edges. [ABSTRACT FROM AUTHOR]

The finite element model of a tubular member under the combined action of axial compression, creep, and axial impact was constructed with the numerical analysis software, to evaluate the core concrete creep effect on the dynamic responses of a steel tubular member in axial compression. In the model, the creep effect of core concrete of different age is equivalent to the change of its elastic modulus. Then, the dynamic responses of a tubular member in axial compression and impact were simulated considering the creep effect, time-history curves of impact load, contact time, axial deformation, stress and strain were plotted, and the effect of creep on them was discussed. The impact load peak decreases with the development of the core concrete creep, and the most is about 51%; the contact time and axial deformation increase; the concrete stress decreases, but the concrete strain increases greatly. The minimum and maximum principal concrete strains after 30 years exceeded those after 28 days by 6.35 and 8.6 times, respectively. The core concrete creep has a less effects on the stress and strain of the steel tube. The fruits provide a scientific help for the impact resistance design of a concrete-filled steel tubular member in axial compression. [ABSTRACT FROM AUTHOR]

Concrete filled steel tube (CFST) columns are the main loaded elements in the structures as they provoke the superior mechanical properties of constituent materials. However, concrete filled double steel tube (CFDST) columns refer to a new type of composite elements which have very high level of fire resistance and the potential to be implemented in high-rise structures. Columns are exposed to high stresses due to the increasing loads of daily life. Therefore, unpredictable deformations may occur and affect the performance and safety of structures. This article first studies the effectiveness of a concrete filled circular steel tube (CFCST)-based technique for repairing buckled and stressed CFST columns, then it studies the advantages of CFDST columns in improving the capability of composite members. The CFCST-based repairing system is to place the deformed CFST column in a larger diameter steel tube, and then the concrete is poured in the gap between the deformed column and the larger tube. Buckled CFST specimens with different tube tkicknesses were repaired and tested to failure under axial compression. The performance of repaired CFST columns was compared with that of undamaged counterpart columns. Based on findings, it can be concluded that the repair technique restored the capacity of the deformed columns from 97% to 100% of the capacity of the undamaged counterpart columns which confirm the effectiveness of repairing using CFCST-based technique. Results of the study provide significant information to the available test data concerning repairing of CFST members. [ABSTRACT FROM AUTHOR]

Coal-field fire results in much loss of resource and severe harm for human beings. In order to investigate the oxidation and heat transfer characteristics of coal-field fire under axial compression, the coal samples were heated and loaded by stress within axial compression equipped with a temperature-programmed device. Considering the heat generating rates over temperature in temperature-programmed (TP) device, both the critical temperatures Tc and Tg were obtained to divide the process of TP under axial compression into three stages. (Here, Tc is the critical temperature, it indicates that the coal begins to undergo an intense oxidation reaction. Tg represents the burnout temperature, as the temperature reaches Tg, the oxygen supplied to the furnace is almost exhausted and then fuel molecule of coal reacts with oxygen slowly again.) Stage I (less than Tc) represents the process as the temperature of coal increases slowly, Stage II (Tc ~ Tg) the temperature of coal rises rapidly, and Stage III (more than Tg) the temperature of coal combusts steadily. In Stage I, the smaller the apparent activation energy of coal, the lower the critical temperature Tc. The apparent activation energy of coal is the smallest as the axial compression reaches the critical axial compression (4 MPa), and the thermal conductivity of coal decreases with the increasing temperature. In Stage II, the smaller the apparent activation energy of coal, the lower the Tg, and the thermal conductivity of coal goes up and down as 2, 4, 6 and 8 MPa were loaded in turn. Generally, the results show that the average oxygen consumption rate of coal increases as the porosity increases, while the average porosity of coal increases linearly with the decreasing axial compression. Furthermore, the thermal conductivity changes as a cubic function with the increasing axial compression. The results would be meaningful to explain the spread of coal-field fires and provide guidance for the on-site prevention and control for coal-field fires. [ABSTRACT FROM AUTHOR]

Flexible pipes connect the two critical systems of the floating production platform and underwater production, which play an important role in the transportation of oil and gas as well as water injection. However, flexible pipes are often subjected to multiple loads that threaten their stability in the service process. In this study, a model of a flexible pipe containing practical cross section in all layers is established to study the effects of axial compression and wet collapse loads on clockwise and anticlockwise torsional responses. The results of calculation show that the axial compression and radial expansion of the flexible pipe are caused by the axial compression load, which reduces clockwise torsional stiffness. The wet collapse load induces the bending deformation of the flexible pipes in clockwise and anticlockwise torsion, where the bending deformation of clockwise torsion is significantly affected by the change in the Young's modulus of the tensile armor layers. This study shows that clockwise torsional stiffness is small and exhibits a trend of axial compression. Clockwise torsion has poor stability in combination with axial compression and wet collapse loads, respectively. Therefore, to prevent instability in flexible pipes, clockwise torsion load, or which coupled with axial compression and wet collapse load, should be avoided. [ABSTRACT FROM AUTHOR]

The problem of the stability and initial post-buckling behavior of sandwich shells with transversely elastic light-weight filler is solved. The governing system of nonlinear equations is derived with allowance for structural discreteness that allows independent deformation of load-bearing layers. The system is solved with the asymptotic Koiter–Budiansky method. Structures composed of two cylindrical carbon-fiber shells interacting through a spring-type filler are analyzed. It is shown that the critical load under axial compression with like forces falls between the critical loads for the inner and outer shells. In the post-buckling state, the bending modes may be different. It is rational to increase the filler stiffness to a certain level. [ABSTRACT FROM AUTHOR]

In the present study, the finite-element (FE) and experimental analysis were carried out to understand the behaviour of the different cross-sectional configuration of plain concrete and concrete filled steel tube (CFST) short columns. A numerical model for the simulation of columns subjected to axial compression has been established using the commercial software package ABAQUS. The ultimate load carrying capacities of the different configuration of short columns are calculated using ACI-318 code. The results estimated according to the design code are found in good agreement with the FE and measured results. It has been noticed that the ductility of the CFST column is significantly high compared to the concrete alone. The outcome of the study reveals that the circular column profiles are good geometry to be considered, since they have outstanding performance concerning of energy absorption in axial loading condition. Furthermore, it has been noticed that the numerical model shows the satisfactory performance in predicting the failure modes. At the end of the study, it is recommended that the utilization of various grade of concrete layer combination of CFST columns shows a better choice from the economic point of view. [ABSTRACT FROM AUTHOR]

In this paper, a novel numerical simulation framework using meso-scale finite element model is developed to predict the mechanical properties and damage mechanisms for one-layer biaxial braided composite tubes with gradient braided structures in axial direction, which involves braided reinforcements with an evolution of braiding angle. To bridge the relationships between the braiding procedure and geometric model, this paper develops an automatic algorithm that generates the geometric model with requiring braiding parameters as input parameters. The braided fabric model is generated by circularly arraying the yarn model, which is established by sweeping varying cross-sections along the centerline with the control of guidelines. The geometric model of matrix pockets is obtained by extracting the fabric model from the whole geometric model of composite tube. After that, a braiding yarn mesh in hexahedron format and co-node matrix mesh in tetrahedron format are generated from the assembled braided fabric and matrix pockets. The framework established in this paper is validated by comparison with the experimental results of the composite tubes with braiding angles from 36.6° to 49.6° subjected to quasi-static axial compression. [ABSTRACT FROM AUTHOR]

In order to promote the application of angle-steel confined high-strength concrete (ACHC) columns in new construction and reinforcement projects of civil engineering, this paper designs 15 groups of ACHC short columns with a shear span ratio of 1.5 under axial compression by taking the hoop coefficient, strength grade of concrete and yield strength of steel as parameters. Based on the constitutive model of steel and confined concrete and considering hoop effect, the simulation analysis on them was carried out by ANSYS software, and the rationality of finite element modelling is verified by comparing it with the experimental data. The author investigated the influence of different hoop coefficients, different concrete strength grades and different yield strength of steel to the mechanic behaviour of ACHC short columns, and the results show that the influence of hoop coefficient to the bearing capacity and ductility is more significantly than other parameters. Considering the hoop effect of batten plate to concrete, the linear relationship between the influence factor of batten plates and the hoop coefficient is inverted by using 1stopt software. At last, the calculation formula of ultimate bearing capacity of ACHC short columns is gotten, and the design method and suggestion of short columns are put forward. [ABSTRACT FROM AUTHOR]

This paper presents an experimental investigation on concrete-filled double-skin circular hollow section (CHS) cross joints under axial compression. A total of twenty-two right-angled CHS cross joints with different brace to chord diameter ratio (β), inner tube to outer tube thickness ratio of chord (ω) and hollow ratio of chord (χ) were tested, in which eighteen concrete-filled double-skin CHS cross joints were studied for different shapes of inner tube of chord, two traditional empty CHS cross joints and two traditional concrete-filled CHS cross joints were tested for comparison. The joint strengths, failure modes, load-deformation curves and strain distribution curves of all specimens are reported. The effects of brace to chord diameter ratio (β), inner tube to outer tube thickness ratio of chord (ω), hollow ratio of chord (χ), shape of inner tube of chord and concrete strength on the behaviour of concrete-filled double-skin CHS cross joints under axial compression were evaluated. It is shown from the comparison that the ultimate load and initial stiffness of CHS cross joints are significantly enhanced by strengthening the chord member with inner tube and concrete infill. Furthermore, the ultimate strengths are increased with the increase of the β ratio, whereas the ultimate strengths are decreased with the increase of the χ ratio for all types of concrete-filled double-skin CHS cross joints. On the other hand, the ultimate strengths are enhanced with the increase of the ω ratio and concrete strength for all types of concrete-filled double-skin CHS cross joints, but the enhancement is insignificant. The corresponding finite element analysis was also performed and calibrated against the test results. The design equations are proposed based on the test and finite element analysis results for concrete-filled double-skin CHS cross joints, which are verified to be more accurate. [ABSTRACT FROM AUTHOR]

This study outlines the experimental investigation of the steel tube columns filled with selfcompacting concrete under axial compression. The effect of the stiffening arrangements and the concrete strength on the properties of the concrete-filled steel tube columns having stiffeners of different geometric dimensions has been investigated. The failure modes, ultimate loads, stiffness, ductility and strain response of the concrete-filled steel tube columns during the experiment have been analyzed. The results imply that the local buckling of the steel tubes can be delayed by the stiffeners. Moreover, the specimen with the four-sided stiffening arrangement possesses higher stiffness and better ductility as compared with the two-sided one. The test results also demonstrate that the proposed stiffening schemes can improve the ultimate compressive capacity. The predicted ultimate loads have been compared using the existing codes, and the modified formula has been proposed. A good agreement between the theoretical and the experimental results is observed. [ABSTRACT FROM AUTHOR]

Frame stringer-stiffened shell structures show high load carrying capacity in conjunction with low structural mass and are for this reason frequently used as primary structures of aerospace applications. Due to the great number of design variables, deriving suitable stiffening configurations is a demanding task and needs to be realized using efficient analysis methods. The structural design of ring frame stringer-stiffened shells can be subdivided into two steps. One, the design of a shell section between two ring frames. Two, the structural design of the ring frames such that a general instability mode is avoided. For sizing stringer-stiffened shell sections, several methods were recently developed, but existing ring frame sizing methods are mainly based on empirical relations or on smeared models. These methods do not mandatorily lead to reliable designs and in some cases the lightweight design potential of stiffened shell structures can thus not be exploited. In this paper, the explicit physical behaviour of ring frame stiffeners of space launch vehicles at the onset of panel instability is described using mechanical substitute models. Ring frame stiffeners of a stiffened shell structure are sized applying existing methods and the method suggested in this paper. To verify the suggested method and to demonstrate its potential, geometrically non-linear finite element analyses are performed using detailed finite element models. [ABSTRACT FROM AUTHOR]