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• A vertically oriented double corrugated steel plate shear wall is proposed. • The elastic buckling behavior of the wall is affected by the bolt spacing. • The compressive and shear stability coefficients are established. • The stability of the wall affects the correlation curve of N/N u - V / V u. As a novel structural component, the Double Corrugated Steel Plate Shear Wall (DCSPSW) is formed by interlocking two corrugated steel plates using high-strength bolts. This paper investigates the global stability design methods for DCSPSWs under combined shear and compression loads. Firstly, this paper examines the elastic buckling performance of DCSPSWs under horizontal shear loads and vertical compression loads separately. A bolt spacing factor (η) is introduced to reflect the influence of bolt spacing on the elastic buckling stress of DCSPSWs. Then, based on extensive finite element analysis (FEA), this paper investigates the elastoplastic buckling behavior of DCSPSWs under shear loads and compression loads and establishes the corresponding stability curves to predict ultimate load-bearing capacity. It is found that the stability coefficients (φ s and φ c) are closely related to the normalized slenderness ratios (λ ns and λ nc). A smaller bolt spacing allows the DCSPSWs to exhibit improved elastic and elastoplastic stability. Finally, this study investigates the load-bearing performance of DCSPSWs under combined shear and compression loads and proposes the design formulas. The results show that the correlation curve of N / N u - V / V u can provide a conservative and accurate design. The research findings of this paper are advantageous for promoting the application of the innovative DCSPSWs. [Display omitted] [ABSTRACT FROM AUTHOR]

This paper presents a numerical investigation on the local buckling behaviour of high strength steel (HSS) and hybrid I-sections under axial compression, which has not been comprehensively discussed in previous literature. Three sectional steel combinations, featuring different web strength grades (Q690, Q460, and Q355) and using HSS Q690 flange plates, were studied. Through the validated numerical method, parametric studies on the effect of web strength grade, boundary condition and plate slenderness were carried out. The design specifications in European, Australian, and American codes were evaluated using the results of 243 numerical models and collated test data. In addition, the continuous strength method (CSM), direct strength method (DSM), and Kato's method, which can account for element interaction were extended to design for the local buckling behaviour of HSS and hybrid I-sections subjected to axial compression. Assessment results showed that ANSI/AISC 360-16 provides more accurate results than Eurocode 3 and AS 4100. Statistical and reliability results demonstrated the satisfactory reliability level of the proposed design expressions for CSM, DSM, and Kato's design methods. This paper provides insight into the local buckling behaviour and mechanism behind plate interaction of hybrid I-sections. • Three web strength grades-Q690, Q460 and Q355 are considered for welded I-sections with Q690 flange. • A parametric study of 243 numerical models for welded I-sections under axial compression is carried out. • Critical plate element governs the local buckling behaviour of welded I-sections in compression. • Normalised ultimate loads of welded I-sections are marginally affected by the web strength grade. • Newly developed design methods, including the direct strength method, the continuous strength method, and the method by Kato are extended. [ABSTRACT FROM AUTHOR]

• In order to improve the bonding strength between the structures, a new fiber-reinforced CorTube structure is designed and fabricated. • The auxetic characteristic and the effective young's modulus of the structure are analyzed theoretically, and the relationship between the configuration parameters and the theoretical solutions is discussed. • The deformation characteristics and failure forms of the structure under low-speed impact load are studied. • The influence of impact position and impact energy on the mechanical properties of the structure is revealed. Auxetic structures are gaining great attention due to their unique contraction deformation characteristics under compression and impact. In this paper, high performance carbon fiber-reinforced composites are used to fabricate the auxetic structure consist of corrugated sheets and tubes (CorTube). The quasi-static uniaxial compression and low-velocity impact properties of composite CorTube structure are explored. The response of the composite CorTube structures under quasi-static compression loads are analyze through a combination of theoretical analysis, simulations, and experimental tests. Additionally, drop-weight impact tests are conducted using a rigid impactor with a hemispherical head to examine the effects of impact energy levels, impact locations, and corrugated sheet thickness on the impact response of CorTube structure. Enhancing corrugated sheet-tube bonding via modified cross members and reducing tube crushing during quasi-static compression are notable findings. The results also highlight the remarkable auxetic properties of the composite CorTube under low-speed impact, and the impact resistance could be enhanced by increasing the corrugated sheet thickness and stiffness. Various failure modes were observed, including cracks, pits, tube crushing, and delamination. Significantly, peak-impacted specimens exhibited greater maximum displacement with lower peak impact forces. This study offers insights into the deformation and failure modes of auxetic CorTube structures under low-velocity impact. [ABSTRACT FROM AUTHOR]

The concept of local buckling of compressed isotropic cylindrical shells is developed in this paper. Buckling of axially compressed cylindrical shells under different types of local perturbations has been studied in many theoretical and experimental researches. Different methodologies, based on these studies, were suggested for design buckling load estimation. However, in most calculations and experiments only two classical boundary conditions were considered: fixed displacement of the shell edges in the axial direction or fixed and uniformly distributed compressive load. Both of them are hard or even impossible to realize in practical applications. In the present paper we studied the shell behaviour with 6 different types of boundary conditions, which included the above mentioned two types. We considered shell loading through rigid plates with different types of possible displacements (degrees of freedom) and through stiffening ribs at the edges of the shell. Two theoretical methods were applied: numerical (finite element method) and analytical (Pogorelov's geometrical method). Lateral force was applied as a perturbation and stability of the shell under load combination was studied. The results of calculations were compared with obtained experimental data for validation of numerical solutions. Then metastability and post-buckling behaviour of the structure was studied using theoretical and experimental methods. In particular the interval of existence and stability of post-buckling equilibrium states of the shells with one or several buckles was studied systematically. The post-buckling equilibrium paths and corresponding energy barriers for all mentioned types of boundary conditions were analyzed. Parametric analysis of boundary value problem allowed to establish the main (Batdorf) structure parameter. Formula for design buckling load was suggested and discussed. • The effect of boundary conditions on stability of compressed cylindrical shells under local perturbations is studied. • Results obtained by numerical method are validated by comparison with experimental data. • Post-buckling behaviour and metastability of the structure was studied using analytical, experimental and numerical methods. • Analysis of boundary value problem allowed to establish the main (Batdorf) structure parameter. • Formula for design buckling load is suggested and discussed. [ABSTRACT FROM AUTHOR]

Concrete-infilled double steel corrugated-plate walls (CDSCWs) are composed of two steel corrugated-plates (SCPs) which are connected through bolts, and concrete filled the spacing formed between the two SCPs. Two vertical boundary elements are installed additionally at both sides of CDSCWs. On the one hand, the corrugated configuration of SCPs has great improvement on the load-bearing efficiency of CDSCWs; on the other hand, much higher bearing capacities and better seismic performance for CDSCWs are provided owing to the interactions among SCPs, bolts and infilled-concrete. This paper investigates the load-bearing mechanism and strength design formulae of CDSCWs under compressions. Since SCPs are prone to local buckling failure between two rows of bolts under the conditions of large vertical bolt spacing and small thickness of SCPs, this paper mainly focuses on the load-bearing mechanism of SCPs in CDSCWs under uniform compressions. The unilateral constraint on SCPs provided from infilled-concrete and the restraining effect on the flexural deformation of SCPs owing to bolts are considered. At first, series of finite element (FE) eigenvalue buckling analyses are conducted to study the elastic buckling behavior of SCPs subjected to uniform compressions. On the basis of Euler's formula, the formulae for predicting the elastic buckling stresses and corresponding normalized slenderness ratios λ s of SCPs are achieved respectively. The instability performance of SCPs under uniform compressions is then investigated through FE nonlinear analyses, and accordingly the stability coefficient φ s is attained. The corresponding φ s − λ s curve is therefore established in order to calculate the ultimate bearing capacities of SCPs. In addition, the cooperative performance of material strengths between SCPs and concrete is analyzed numerically when CDSCWs reach their compressive ultimate strength. With this consideration, the design method for predicting the cross-sectional strength of CDSCWs under compressions is proposed. Moreover, a CDSCW specimen with I-section is tested under a compressive load. Its cross-sectional strength is investigated experimentally. The results of the experiment coincide with those of numerical simulation, this verifying the safety and validity of the design method for cross-sectional strength design of CDSCWs. • CDSCWs have favorable load-bearing capacities and great seismic performance. • FE eigenvalue buckling analyses are used to investigate the elastic local buckling behavior of SCPs in CDSCWs under uniform compressions. • FE elastoplastic analyses are used to study the load-bearing mechanism of CDSCWs under uniform compressions. • Cross-sectional strength design formulae for CDSCWs under uniform compressions are proposed. • A CDSCW specimen with I-section is designed and its cross-sectional strength is investigated experimentally. [ABSTRACT FROM AUTHOR]

Abstract The present paper introduces two types of inner cellularization geometry in the thin-walled cylinders derived from previous studies on this area of subject. Novel geometries were proposed in this research. These configurations were the result of modifications to the previous works. Moreover, these absorbers were proposed to increase the specific energy absorption, reduce the peak energy, and improve crushing. The maximum Specific Energy Absorption (SEA), minimum Initial Peak Crushing Force (IPCF) under quasi-static axial compression test at the rate of 10 mm/min, and thickness and height parameters of the thin-walled cylinder and length of the inner square's sides were considered the design variables to achieve the optimal state. In the present work, two DOEs (design of experiment) were performed in Design-Expert in accordance with the given surfaces for both geometries of the thin-walled cylinder's inner cores. Subsequently, for further investigation, the experimental results were compared with those obtained from the finite element simulation in Abaqus, revealing the desirable accuracy of the results. Finally, by applying the equations derived from the proposed model to each of the responses and geometries, their optimal states were obtained using both the desirability approach in Design-Expert and the MOPSO method in MATLAB. Thickness had the highest impact on both configurations. Moreover, the optimal thickness for both configurations was 1.4 mm in the selected range. As regards the multi-objective function, the best inner square edge lengths for the C2R and S2R configurations were the central and upper limits, respectively. Finally, the cylinder heights for the C2R and S2R geometries were 174 and 153 mm, respectively. Highlights • The present paper introduces two types of inner cellularization geometry in the thin-walled cylinders derived from previous studies on this area of subject. In the present investigation, the quasi-static compressive experimental and numerical simulation test cylindrical absorbers is discussed. • The thin-walled cylindrical energy absorbers are considered with combined hybrid geometries and novel internal cells. • The response surface method (RSM), which is one of the design of experiments (DOE) techniques has been used to examine the effect of the parameters on energy absorption. • The equations derived from the proposed model for each of the responses and each geometry. • Optimal states were also obtained using both the desirability approach in Design Expert software and MOPSO method in MATLAB software. [ABSTRACT FROM AUTHOR]

In traditional end plate column splices, bolts are placed double symmetrically on the four sides of square hollow sections (SHS). In order to reduce the required gap between the façade and the column, the end plate could be flushed on one or two sides of SHS for the column along the façade or at the corner of a building, respectively. However, the analytical solution (Component method) for the traditional column splice is not applicable in this case. This paper addresses the tensile behaviour of asymmetric column splices, where a cover plate is used on the end plate flushed side. Columns are dominantly loaded in compression and bending, but to verify the component's interaction, the column splices are tested in tension in this paper. The tensile behaviour is investigated through the experiment, the finite element (FE) analysis, and the component method. Eight tensile tests were conducted. The FE model is validated against the experiment. A bi-linear model is employed to characterise the column splice yield resistance, which shows a good agreement with the ultimate resistance of the FE model using a constitutive model without strain hardening. The effective length measured from the FE model is approximately two times that calculated by equations. Using the measured effective length, the component method predicts the characterised yield resistance well (average 13% lower). In comparison, the resistance is underestimated by 35% on average if the calculated effective length is used. [Display omitted] • The behaviour of the asymmetric bolted column splice is investigated experimentally. • 3D DIC is used to reveal the internal force distribution at different deforming stages. • The column splice yield resistance is characterised based on a bi-linear model. • The component method is used to predict the column splice resistance. • The effective yield line length is measured from the validated finite element model. [ABSTRACT FROM AUTHOR]

This paper presents an experimental investigation and a finite element analysis on web-stiffened cold-formed lipped channel columns with batten sheets connected between the column's two lips at reasonable space. Initially, the paper presents the static compressive test results on 18 specimens under pinned-end restraint conditions with different column length and load eccentricities considered. It is shown that the batten sheets exert significant influence on both the buckling modes and the ultimate strength of the specimens under positive eccentric loading and/or axial loading conditions, while they just have few impacts on that of the specimens under negative eccentric compression. Strengthened by the batten sheets, the columns performed obviously higher ultimate strength under axial and positive eccentric compression compared with the ones without batten sheets and the strengthening effect increase with the increase of column length. Furthermore, the tested specimens were also numerically investigated by finite element program of ANSYS. Geometric and material nonlinearities were both included in the finite element models and it is demonstrated that the numerical analysis can closely predict the ultimate strength and the buckling behavior of the tested columns. Finally, a parametric study was conducted by using program of ANSYS, in which effect of the increasing lip stiffener width and varying batten sheet space were all investigated and it is concluded that the contribution of the batten sheets to the columns’ strength decreased notably with the increasing lip width or batten sheets’ space for axial and/or positive compressed columns. The best choice of the distance between batten sheets (d≤λ/3) for axial compressed lipped channel columns must also be a reasonable choice for positive compressed columns. [ABSTRACT FROM AUTHOR]

• Achievement of high strength Al/CFRP hybrid joint via laser texturing pretreatment. • High friction stir joining speed which reached 3000 mm/min. • Establishing evaluation criteria of laser-textured joint: anchorage value. • Analysis including the semi-crystalline property of PA66 and temperature simulation. This paper presents the achievement of a high-strength Al/CFRP hybrid joint through a high-speed friction stir lap joining process, combined with variations in laser surface texturing pretreatment parameters. The study examined the impact of laser surface texturing parameters by varying the depth, interval distance and width of the laser texture. By adjusting laser texturing parameters, the softened PA66 was fully infused into the textured grooves on the aluminum surface, leading to a significant reduction in interfacial voids and cracks in Al/CFRP. The preliminary tensile shear test showed that the hybrid joint broke at the CFRP base material, indicating that the laser texturing exhibited excellent Al/CFRP interface strengthening ability. Further compression shear tests were applied to reveal the actual interfacial load-carrying performance for comparison. The maximum shear strength of 25. 5 − 1.34 + 0.7 MPa was achieved at a joining speed of 3000 mm/min. Additionally, a mathematical model was proposed to assess the strengthening impact of laser texturing parameters, considering micro-texture geometry and interfacial defects. The tearing of PA66, detachment of carbon fibers, and the breakage of carbon fibers were the three primary types of fracture modes identified at the Al/CFRP interface. The joining mechanism revealed that both mechanical interlocking and the chemical bonding of Al-O-C contributed to the increase in joint shear strength. This study presents a credible method for producing high-strength Al/CFRP lightweight structures. [ABSTRACT FROM AUTHOR]

• Investigates corroded steel tubular members' behavior under eccentric loads. • Reveals corrosion thickness's crucial impact on structural integrity. • Explores the significant role of patch angle in buckling and failure modes. • Highlights the vulnerability of corroded structures under even minor eccentricities. • Challenges AS 4100:2020′s overestimation of critical load capacity. This paper investigated the compressive behaviour of locally corroded steel tubular members under both concentric and eccentric loads, revealing insights into the effects of corrosion thickness and patch angle on failure and buckling behaviour. A direct relationship between corrosion thickness and structural integrity was found in this study, highlighting the significant impact of corrosion on the columns. Moreover, the patch angle's influence on buckling and failure modes emphasises the role of geometric considerations in evaluating these members. Notably, an evident linear reduction in loading capacity occurs as the patch angle increases, irrespective of loading conditions, underscoring the need to account for geometric factors. In addition, even minor eccentricities lead to a substantial decrease in the compressive capacity, further emphasizing the vulnerability of corroded structures. By comparing the effects of corroded patch angle and depth on capacity reduction, the study underscores a steeper reduction gradient with patch angle. The established linear relationships between volume loss due to corrosion damage, centroid shifted distance, and ultimate compressive load capacity provide valuable insights for capacity prediction. Moreover, this study evaluates the applicability of conventional prediction methods like AS 4100:2020, which tends to overestimate critical load capacity for locally patch-corroded members. As an alternative, a proposed formula is presented, exhibiting enhanced accuracy with lower errors compared to existing models. [ABSTRACT FROM AUTHOR]

Along with proposing any innovative structural element for design purposes it is necessary to understand its behaviour under combined structural actions. This paper includes experimental, numerical and analytical investigations on an innovative type of hybrid fabricated section consisting of high strength tubes and mild steel plates under the effect of axial compression and bending moment interaction. As a special case of interactive condition, pure bending performance of the hybrid fabricated member is examined with focus on the local failure mechanisms and analytical expressions are proposed to predict the moment resisting capacities. Furthermore, compression-bending interaction curves are obtained from plastic analysis of hybrid hollow sections and compared to relevant standard formulations. The compression-bending curves obtained for various ratios of tube cross-section and strength to that of plate show that a linear interaction formula is applicable to predicting the plastic interaction behaviour of sections with high ratios while sections with lower ratios are closely predicted by a bilinear interaction formula. This paper also includes beam-column tests accommodating combined effects of compression, bending and also shear. Employing the developed and validated finite element model, a parametric study is conducted on the effect of section geometry and material on the axial-lateral interaction of beam-columns. Referring to the member interaction results, reaching an optimum interactive performance stands on the design of both geometry and material of plate and tube elements. [ABSTRACT FROM AUTHOR]

The calculation method of the composite reinforced panel structure's limit load capacity is investigated. A theoretical method is proposed to establish the constitutive equations, which disassembles the reinforced panel into several parts (i.e., skin, web, and flange) and predict the structure's limit load capacity by performing buckling analysis and failure analysis on these parts respectively. The finite element analysis is employed to simulate the instability path of the structure according to cohesive zone model (CZM) and the secondary development in USDFLD (user subroutine to redefine field variables). The accuracy of simulation model is verified by strain assurance criterion. The results are compared with the experimental values, which confirm the reliability and feasibility of the theoretical method and finite element analysis. This study could provide references for the calculation method of limit load capacity and promote composite's application in civil aircraft. • This paper investigates the panel's bearing capacity and proposes a new theoretical analysis method. • In the FEM analysis, the cohesive zone model (CZM) and the secondary development in USDFLD effectively improve the calculation accuracy. • The accuracy of finite element simulation model is verified by strain assurance criterion (SAC). • This paper summarizes the preparation process of the composite specimen under compression load, which could be used as industry standards and provide certain guidance for similar tests. [ABSTRACT FROM AUTHOR]

This paper aims at investigating the structural response and predicting the ultimate strength of the cold-formed built-up I-section columns affected by local, distortional, global and in particular by the local-distortional (LD) interactive and local-distortional-global (LDG) interactive buckling modes. For this purpose, a total of 18 single C-section columns and 18 built-up I-section columns were tested under uniaxial compression load, respectively. The cross-sectional dimension, the thickness and the length of the tested members were varied in the test so as to cover a wide range of local, distortional and overall slenderness. It was shown in the test that noticeable LD interaction was observed for a built-up column with short length as well as LDG interaction for a built-up column with intermediate length. Due to the clear evidence obtained in the test that LD and LDG interactions cause substantial ultimate strength erosion in cold-formed built-up I-section column, a novel direct strength based method was proposed in this paper to quantify such an erosion effect. The validity of the proposed method was then verified by comparing the results obtained from the proposed method with the test results in this paper as well as several other test results in the literature. The comparison results proved that the proposed method can be used successfully in estimating the ultimate strength of cold-formed built-up I-section column affected by pure buckling mode as well as interactive buckling mode. [ABSTRACT FROM AUTHOR]

This paper presents an experimental study into the axial compressive behaviour of self-compacting concrete filled elliptical steel tube columns. In total, ten specimens, including two empty columns, with various lengths, section sizes and concrete strengths were tested to failure. The experimental results indicated that the failure modes of the self-compacting concrete filled elliptical steel tube columns with large slenderness ratio were dominated by global buckling. Furthermore, the composite columns possessed higher critical axial compressive capacities compared with their hollow section companions due to the composite interaction. However, due to the large slenderness ratio of the test specimens, the change of compressive strength of concrete core did not show significant effect on the critical axial compressive capacity of concrete filled columns although the axial compressive capacity increased with the concrete grade increase. The comparison between the axial compressive load capacities obtained from experimental study and prediction using simple methods provided in Eurocode 4 for concrete-filled steel circular tube columns showed a reasonable agreement. The experimental results, analysis and comparison presented in this paper clearly support the application of self-compacting concrete filled elliptical steel tube columns in construction engineering practice. [ABSTRACT FROM AUTHOR]

• The structural performance of G550 high strength cold-formed steel built-up OI-section and CB-section columns under axial compression was studied. • 20 axial compression tests on G550 high strength cold-formed steel built-up section columns were carried out. • FE models were developed and validated against test results and then used to perform parametric studies. • The current design methods were evaluated for their applicability to G550 high strength cold-formed steel built-up OI-section and CB-section columns under axial compression. • The modified direct strength method was proposed and shown to improve design accuracy. This paper investigates the buckling behaviour and load-carrying capacity of G550 high strength cold-formed steel built-up section columns under axial compression through experiments and numerical simulations. Two types of built-up sectional profiles were formed, which were defined as built-up OI-section and built-up CB-section. Each built-up OI-section member is formed by connecting two cold-formed steel C-section members in a back-to-back manner using self-drilling screws, while each built-up CB-section member consists of a cold-formed steel C-section member and a cold-formed steel U-section member, which are connected in a face-to-face manner by self-drilling screws. The experimental programme included tensile coupon tests, initial geometric imperfection measurements and 20 pin-ended column compression tests. In the numerical modelling programme, finite element models were developed and validated against the experimental results, and then used for parametric analyses to generate a total of 250 numerical data with different cross-section dimensions and member lengths. Based on the experimental and numerical data, the accuracy of both the effective width method and the direct strength method for predicting the strengths of G550 high strength cold-formed steel built-up section columns, as set out in the American Specification, was evaluated. The evaluation results indicated that both the effective width method and direct strength method provided accurate and consistent failure load predictions for G550 high strength cold-formed steel built-up OI-section columns on average, but with some unsafe failure load predictions, while the predicted failure loads were inaccurate, scattered and conservative for G550 high strength cold-formed steel built-up CB-section columns. Moreover, the effective width method and direct strength method yielded a similar level of design consistency for G550 cold-formed steel built-up section columns, but the direct strength method resulted in more accurate and less conservative failure load predictions than the effective width method. The modifications to the codified DSM equations were proposed for G550 high strength cold-formed steel built-up section columns and shown to provide improved predictions of failure load over the design codes. [ABSTRACT FROM AUTHOR]

• Out-of-plane stress-strain response of a sandwich panel differs from that of cellular core. • Adhesive height determines densification initiation strain. • Method correctly characterizes densification region, accounts for adhesive effect. • Significant energy absorbed in the densification region for panels with adhesive. • Larger fillets reduced the overall absorbed energy due to lower densification initiation strains. Lightweight aluminum honeycomb sandwich panels are widely used in industrial engineering, particularly in aircraft applications. Due to their thin-walled nature, the honeycomb cell walls are especially susceptible to buckling under out-of-plane compressive loading, while the adhesive fillet that secures the honeycomb to the face-sheet remains intact. This paper investigates the effect of the adhesive geometry and bonding constraints on the out-of-plane compressive response through experimental, Finite Element (FE), and mathematical methods. A hybrid method accounting for adhesive bonding between the face-sheet and the cell walls, and different adhesive fillet geometries was proposed to predict strain onset and stress-strain relationships during densification. The resulting stress-strain curves predicted the energy absorbed by the panels to within 3.5 % of the experimental results. The widely used material model for honeycomb core does not account for densification and underpredicted the absorbed energy by 15.6 %. These findings emphasize the need for detailed adhesive analysis in the design of lightweight, thin-walled sandwich structures. [ABSTRACT FROM AUTHOR]

The present paper focusing on the most important energy absorbing system of the circular thin-walled tubes or shells under lateral compression between two rigid plates, which is also a basic mechanical issue, studies the cross-sectional deformation in terms of the compressive force applying to the tube in the large elastic–plastic deformation stage during the lateral compressive process by both theoretical as well as finite element analysis (FEA) methods. Firstly a FEA simulation for the thin-walled tube's lateral compressive process between two parallel plates is carried out to analyze the mechanical response and deformation characteristics, and then it is validated by tube's lateral compressive experiment using digital image processing technology. Following the simulation results, some assumptions are proposed for theoretical derivation. Secondly focusing on the large elastic–plastic deformation stage (Stage II, in this paper), the compressive deformation of thin-walled tubes is divided into elastic and plastic regions according to the von Mises yield criterion. In elastic region the linear strain–displacement relations of shell theory and Hooke's stress–strain relations are employed, and in plastic region the nonlinear large strain–displacement relations of doubly-curved shell theory and the power hardening rule are employed. Then considering both geometric and material nonlinearities, the equilibrium equation, which is a complicate integral equation with the variable upper limit, is derived using the principle of virtual work. It is solved by expanding the integrand as a set of polynomials power series. Then the predicted cross-sectional deformation in terms of the compressive force can be obtained by the iterative method. Finally some lateral compressive simulations involving various tubes with different geometric parameters are carried out, and the theoretical model is validated by comparison of the cross-sectional profiles predicted by theoretical model with those obtained by the simulations as well as other methods. At the same time, the applicable conditions of this model are discussed. This paper will play a positive role in studying the cross-sectional deformation for various shells under lateral compression in different application areas. • Mechanical response and deformation characteristics are presented by FEA, which have been validated by compressive experiment. • A new theoretical is derived to predict the cross-sectional deformation in the large elastic-plastic deformation stage of the laterally compressed thin-walled tubes. • A new method is proposed to solve the unintegrable equation with the variable upper limit during the theoretical derivation. • The applicable conditions of this model are given. [Display omitted] [ABSTRACT FROM AUTHOR]

The paper presents an experimental investigation of the local buckling of high strength steel Q460C, Q550D and Q690D welded thin-walled rectangular hollow sections (RHS) under combined compression and bending. Twenty-two short columns, of which five were fabricated from Q460C, twelve from Q550D and five from Q690D, under eccentric compression were loaded to failure. The local buckling behaviors are examined and the ultimate carrying capacities obtained from the test, as well as the numerical modeling reported in the existing literature, are compared with the results obtained from the American Specification ANSI/AISC 360-16, Eurocodes BS EN 1993 − 1 − 1 and BS EN 1993 − 1 − 5 , Chinese Standard GB 50017–2017 and Australian Standard AS 4100: 2020 to determine whether these technical standards are applicable to the high strength steels with nominal yield stress of 460 MPa, 550 MPa, 690 MPa and 960 MPa. The results indicate that the ANSI/AISC 360-16 generally overestimates the ultimate load carrying capacities and will need to be revised for the high strength steels, and the BS EN 1993 − 1 − 1 , BS EN 1993 − 1 − 5 and GB 50017–2017 are in excellent agreement with the experimental or numerical results and thus suitable for the high strength steels over the range of the parameters studied herein, and the Australian Standard AS 4100: 2020 is very conservative. • An experimental investigation of the local buckling of high strength steel Q460C, Q550D and Q690D welded thin-walled rectangular hollow sections (RHS) under combined compression and bending is reported in this paper. • The local buckling behaviors of high strength steel Q460C, Q550D and Q690D welded thin-walled RHS under eccentric compression are examined. • The ultimate carrying capacities obtained from the test, as well as the numerical modeling reported in the existing literature, are compared with the results obtained from the American Specification ANSI/AISC 360-16, Eurocodes BS EN 1993 − 1 − 1 and BS EN 1993 − 1 − 5 , Chinese Standard GB 50017–2017 and Australian Standard AS 4100: 2020 to determine whether these technical standards are applicable to the high strength steels studied in this paper. • The results indicate that the ANSI/AISC 360-16 generally overestimates the ultimate load carrying capacities and will need to be revised for the high strength steels, and the BS EN 1993 − 1 − 1 , BS EN 1993 − 1 − 5 and GB 50017–2017 are in excellent agreement with the experimental or numerical results and thus suitable for the high strength steels over the range of the parameters studied herein, and the Australian Standard AS 4100: 2020 is very conservative. [ABSTRACT FROM AUTHOR]

The coupled effect of geometric and material nonlinearity existing in the buckling process of the stiffened plates sometimes makes it difficult to evaluate their ultimate load capacity numerically. Therefore, so far, experimental tests are still indispensable in the design process of a complicated structure. However, the experimental methods for predicting the whole buckling process of a stiffened plate subjected to in-plane compressive load are still not well developed. In this paper, the fundamental element in the complicated bearing structures, stiffened plate, was set as the object, and its buckling process was deeply analysed. Then, a set of similarity criteria for the stiffened plate subjected to compressive load were proposed based on the Buckingham's Pi theorem, by which the designed scale models for experimental tests could keep similar to the real structures in the whole loading process. Then, the similarity criteria were verified by numerical simulations and experimental tests with different scale models. The work presenting in this paper may potentially contribute to improving the precision of the experimental prediction of the structural ultimate load capacity and the corresponding optimization works. • Similarity criteria for the buckling process of stiffened plates subjected to compressive load were theoretically derived. • Numerical simulations proved that the derived similarity criteria could be widely used. • Experiments were conducted to validate the criteria. [ABSTRACT FROM AUTHOR]

In the field of structural engineering the design of cost efficient structures is highly important. This led to the development of cold-formed steel structures (CFS). An advanced CFS structure is introduced in this paper, which uses a special type of polystyrene aggregate concrete (PAC) as bracing material. This material has beneficial insulating and fire protection properties, which makes it a reasonable choice for residential buildings. An experimental programme was performed, to gain information on the flexural and axial behaviour of PAC-encased CFS elements and panels. Both unbraced and braced members were tested to gain information on increment of load-bearing capacity. Several different element sizes were used to be able to investigate the different stability failure modes (i.e. local, distortional and global). Results showed that PAC was able to restrain the global and distortional buckling modes of steel elements, thus providing “full bracing” in most practical cases. These results are introduced in two papers (Part I and II), detailing the failure modes, load increments and the effect of composite action. In this paper – Part II – the background and the results of compression tests are presented, and the bending experiments are detailed in Part I [1] . [ABSTRACT FROM AUTHOR]

A comprehensive experimental and numerical investigation into the structural performance of stainless steel circular hollow sections (CHS) under combined compression and bending moment has been performed and is fully reported in the present paper and its companion paper. The experimental programme employed four CHS sizes made of austenitic stainless steel, and included material tensile coupon tests, four stub column tests and twenty combined loading tests. The initial loading eccentricities for the combined loading tests were varied to provide a wide range of bending moment-to-axial load ratios. In conjunction with the testing programme, a numerical modelling programme was performed to simulate the experiments. The developed FE models were shown to be capable of replicating the key test results, full experimental curves including the post-ultimate range and deformed failure modes. Upon validation of the FE models, a series of parametric studies were conducted in the companion paper, aiming at extending the current test data pool over a range of cross-section sizes and combinations of loading. The experimental data, together with the generated parametric study results, were analysed and employed to evaluate the applicability of the codified provisions given in the European code, American specification and Australia/New Zealand standard for design of CHS under combined loading. Improved design rules were also sought through extension of the deformation-based continuous strength method (CSM) to the case of stainless steel CHS under combined loading. [ABSTRACT FROM AUTHOR]

Lateral buckling is a main failure mode controlling the strength of C- and Z-section purlins under wind suction, as the compressive flange of cross-section is laterally free in this case. The lateral buckling of roof purlins is different from the normally considered simply supported beams, because the top flange of cross-section of these purlins is laterally restrained due to the bracing of the above roof sheeting. To reveal the lateral buckling of C- and Z-section purlins with their top flanges horizontally restrained, two representative buckling theories for the lateral buckling of thin-walled beams, the traditional buckling theory and a new theory recently proposed by the authors of this paper, are adopted in this study. Comparisons made in this study indicate that the total potentials derived from these two theories have different expressions for the considered purlins. Subsequently, the finite element (FE) analysis using the shell element modeling is adopted to examine the buckling loads of purlins based on these two buckling theories, which indicates that the buckling theory proposed by the authors of this paper is more reasonable for this problem. Simple solutions are also proposed for buckling loads of C- and Z-section purlins with their top flange horizontally restrained, and very good agreements are achieved in the comparisons between the predictions of the proposed solutions and FE results. [ABSTRACT FROM AUTHOR]

This paper examines the buckling of short mild steel cylindrical shells subjected to axial compression. Cylinders were joined together using Metal Inert Gas (MIG) welding process with radius-to-thickness ratio, R / t , ranging from 25 to 100. The axial length of the specimens were assumed to be 111.8 mm. Past result on axially compressed cylinder machined using Computer Numerically Controlled (CNC) machining is compared with fresh experimental results on MIG manufactured axially compressed cylinder. The paper contains a comparison between theoretical predictions, ABAQUS FE results and experimental data for axially compressed cylinder. Details about material testing and collapse test are provided. As compared to the CNC machined specimen, results indicates that there is a good agreement between theoretical prediction, ABAQUS FE results and experimental data for MIG manufactured cylinder with radius-to-thickness ratio, R / t ranging from 25 to 100, with difference ranging between −7% and +2%. [ABSTRACT FROM AUTHOR]

Experimental studies on the behaviour of concrete filled double-skin steel tube (CFDST) subjected to local bearing forces are presented in this paper. Sixteen specimens were prepared and tested with the included angle between bearing member (BM) and compression member of 45° and 90°, whilst both the inner and outer steel tubes of the CFDST specimens are square hollow sections (SHS). The main parameters in the tests were: 1) outside width ratio between BM and compression member: from 0.4 to 0.6; 2) hollow ratio of CFDST: from 0 to 0.6; 3) wall thickness of outer steel tube: 3.05 mm and 3.95 mm; and 4) cross-section of BM: solid and hollow. The failure pattern, load versus deformation curve, bearing capacity and corresponding deformation at bearing capacity of the tested specimens are presented and analyzed. The experimental results show that, while subjected to local bearing forces, CFDST specimens have a high bearing capacity and a good deformation-resistant ability. The calculated bearing capacities of CFDST under local bearing forces using the proposed formulae in the paper are evaluated by comparison with the experimental results. [ABSTRACT FROM AUTHOR]

Lateral–torsional buckling (LTB) resistance of an I-beam depends on the minor axis moment of inertia of its compression flange and torsional rigidity of the section. A practical solution to increase lateral buckling of I-beams is to add two Delta stiffeners between the compression flange and web plates to form a hollow compression flange. Although these beams known as Delta hollow flange beams (DHFBs) have been introduced about half a century ago for bridge construction, however, their LTB behavior has not been investigated, yet. This paper develops a three dimensional finite-element model using ABAQUS for the inelastic nonlinear flexural–torsional analysis of DHFBs and uses it to investigate the effects of unbraced length and central off-shear center loading (located at center, top flange and bottom flange) on their moment gradient factor in different behavioral zones. It was found that the C b factor and moment resistance curve given by AISC-LRFD in Specification for structural steel buildings [2] are not accurate for intermediate (inelastic) and short plastic DHFBs leading to an unconservative design. Therefore, a modified moment resistance equation is proposed to be used instead of the code equation in inelastic zone for the investigated load cases in this paper. [ABSTRACT FROM AUTHOR]

• Composite sandwich cylinders are appealing to anti-collision facilities but existing drawbacks. • Multi-layer lattice-web reinforced composite cylinders have great energy absorption performance. • Double-layer dislocated lattice-web layout could be conductive to the protection of ship and bridge. • Use of bracing makes the composite cylinder exhibit an excellent performance in resisting impacts. This paper reports on the crushing behavior of several novel multi-layer lattice-web reinforced double-braced composite cylinders composed of glass fiber reinforced polymer (GFRP) face sheets, GFRP lattice webs, polyurethane (PU) foam core and steel bars. A series of quasi-static lateral compression and low-velocity impact experiments were carried out to investigate the feasibility of the proposed cylinders. All the experimental specimens were manufactured using a vacuum assisted resin infusion process (VARIP) method. The bearing capacity and energy absorption performance of the composite cylinders can be significantly improved with the enhancement of multi-layer lattice-web layout and use of bracing. Among the proposed three types of lattice-web layouts, the double-layer dislocated lattice-web layout made the composite cylinder exhibit the greatest specific energy absorption (SEA) performance and good impact resistance property and can be chosen as an optimal configuration. Furthermore, numerical models were established using LS-DYNA software to simulate the large deformation of the composite cylinders with double-layer dislocated lattice-web layout. Based on the numerical models, parametric analysis was carried out to discuss the effects of various parameters on the crushing behavior of the composite cylinders. The bearing capacity and impact resistance property can be generally improved with the increase of GFRP thickness or radial lattice-web height. Additionally, using stronger foam material or smaller inclination of bracing can increase the absorbed energy in PU foam but the GFRP material always makes an essential contribution to the energy absorption of the composite cylinders. [Display omitted] [ABSTRACT FROM AUTHOR]

• A stiffener layout adjustment approach together with its procedure is introduced to the existing similarity method for improved processing feasibility of scale-down stiffened plate. • Numerical validation analysis demonstrates that the corrected similarity method yields positive outcomes in modifying the stiffener layouts for stiffened plates while preserving the identical ultimate strength and buckling mode of models. • The corrected similarity method can be utilized to optimize the scale-down model, thus improving precision of experimental studies. This paper proposes a corrected similarity method for designing scaled-down stiffened plates subjected to compression loads that carefully considers conflict between the minimum welding distance and stiffener spacing by introducing a stiffener layout adjustment approach. Reliable plate scenarios were adopted in a numerical parametric study to investigate the effects of different influential parameters on stiffener layout adjustment design, and an empirical formula and associated design procedure for the stiffener layout adjustment approach were proposed. The proposed approach can help engineers obtain scaled-down stiffened plates that are closer to ideal conditions and can improve the precision of experimental studies. [ABSTRACT FROM AUTHOR]

An intrinsic characteristic of components manufactured by the filament winding process is a winding pattern formation during the processing. This paper aims at unlocking and understanding how the winding pattern influences the mechanical behaviour of filament wound cylinders under different boundary conditions. To realize this, a series of finite element models followed by an original geometric approach to generate the pattern are herein developed. Four different patterns and six different winding angles are modelled. These are also modelled by varying the number of layers towards understanding whether there is a correlation between the pattern and the number of layers or not. Three loading cases are considered: axial compression, pure torsion, and internal pressure. Key results reveal that the more layers are stacked to the cylinder, the less impactful is the winding pattern to all loading cases herein investigated. • Multi-layered filament wound cylinders considering the winding pattern. • Systematic FE models to unveil the correlation among winding pattern, winding angle, and number of layers. • Identification of stress fields on different sections of mosaic patterns. • Development of an original pattern generation and implementation into the FE environment. [ABSTRACT FROM AUTHOR]

Offshore structural steel members will need strengthening or repairing due to various reasons. Strengthening is often required due to work over demands or increased environmental loads. Repairing becomes essential as the steel members are usually severely corroded due to the marine conditions. Conventional hot work strengthening and repairing solutions become very expensive and retrofitting using Fibre Reinforced Polymers (FRPs) is an economical alternative. This paper investigates strengthening and repairing of offshore steel tubular members using Carbon Fibre Reinforced Polymers (CFRPs) with the help of experimental testing and an analytical study. Two different specimen sizes which were representative of members in offshore structures namely leg and brace were examined in the study. Partial length strengthening of steel tubular members subject to combined loading of axial compression and bending was carried out using different curing environments (in air and underwater curing). Strengthening and repairing of leg and brace specimens with multiple layers of CFRP retrofitted in underwater conditions were also investigated. Two different consolidation methods (underwater vacuum consolidation and underwater stricture consolidation) were compared with the help of full length strengthening of leg specimens. Although partial length strengthening proved to be less effective, partial length repairing of corroded tubular members were successful in restoring their intact capacity. Full length strengthening for underwater leg specimens were experimentally tested and it was found to improve the structural behaviour in many aspects like ultimate strength, load displacement behaviour, elastic slope, energy absorption, and ductility. A novel technique of underwater vacuum consolidation of retrofit laminates was demonstrated through a set of full length strengthened leg specimens. Underwater vacuum consolidation proved to be advantageous compared to the normal underwater stricture consolidation. An analytical check to identify whether a retrofitted tubular member would reach its target section properties was also introduced. Overall, the paper demonstrates multiple successful applications of FRP composites for underwater strengthening and repairing of offshore steel tubular members. Studies like this expanding the current knowledge on how the FRP retrofitted steel tubular behave within a real offshore structure are essential to increase the uptake of this technology in the oil and gas industry. • Underwater strengthening and repairing of tubular structural members using FRP composites under combined axial compression and bending. • Comparison of difference in the performance between underwater and in-air retrofitting. • Benefits of full length strengthening as opposed to partial length strengthening of tubular members. • Introduction of underwater vacuum consolidation method for application of Fibre Reinforced Polymers on steel structures. • Analytical check predicting the behaviour of retrofitted tubular members under axial compression loads. [ABSTRACT FROM AUTHOR]

Abstract: Stowell's solution [1] for the buckling behaviour of flange elements in compression was premised on the assumption that the element was fixed against flexural rotations at the ends, a condition representing relatively thick elements for which the thickness dimension is adequate to prevent rotations. This paper presents a solution similar to Stowell's which is applicable to pin-ended flange elements. Aspects not considered in Stowell's work, such as the use of elliptic functions to describe the gradual change of mode shape from sinusoidal to essentially linear, and the gradual and asymptotic changes in axial rigidity in the post-buckling range are described in the paper. The paper also presents comparisons between the behaviour of pin-ended and fixed-ended flange elements. Finally, simple strength equations for flange elements in uniform compression based on the first yield criterion are derived. [Copyright &y& Elsevier]

Abstract: The use of cold-formed thin-walled steel structures has increased in recent years, and some built-up section members are motivated and also widely used for their excellent structural behaviors. In this paper, a series of axially-compressed tests on built-up box section members composed of two C-section by self-drilling screws at flanges are conducted. The differences of global, local and distortional buckling behaviors between members with built-up and single sections are investigated at first. Then the effects of installation error and fastener spacing on ultimate load-carrying capacity of built-up members are analyzed. A strength estimation method for built-up members under axial compression is proposed based on the experimental investigation in this paper, as well as some existing experiments, and corresponding numerical analysis studies. Finally, the predicted capacity obtained by using the proposed strength estimation method is compared with experimental results and the nominal axial strength determined according to the AISI provisions, by which the suitability and accuracy of the proposed strength estimation method have been established. [Copyright &y& Elsevier]

Lap-welded steel joints are widely used in steel pipelines for water transmission, and their structural resistance is essential for safeguarding pipeline integrity and functionality after severe earthquakes or other geohazards. These pipelines are thin-walled with a diameter-to-thickness ratio ranging between 100 and 240 and are susceptible to buckling. The present paper is part of a longtime research project on the structural performance of lap-welded steel pipeline joints subjected to severe inelastic deformations, motivated by the need of pipeline safety in geohazards areas. The work described in the present paper focuses on the mechanical behavior, analysis, and design of a new seismic resistant lap-welded joint which was developed to improve the structural performance of lap-welded steel pipelines. Analysis consists of extensive finite element simulations, supported by a series of special-purpose full-scale experiments, on the mechanical response of the new lap-welded joints subjected to severe structural (axial and bending) loading conditions. The proposed joint consists of the standard lap weld configuration, enhanced by a small geometric projection introduced at a specific location near the field-applied fillet weld. The numerical and experimental results demonstrate that under severe compressive loading, this enhancement of the standard lap-welded joint results in consistent and preferential buckling of the steel pipe cylinder and not the lap-welded joint. The proposed joint effectively allows for the steel pipeline resistance to not be limited by the compression capacity of the standard lap-welded joint and offers an efficient, reliable, and economical solution for lap-welded joints in steel water pipelines constructed in geohazard areas. • A small projection is introduced enhancing the standard lap-welded joint. • The projection prevents the buckle to occur at the bell or at the field weld. • Optimum amplitude of the projection is determined with FE simulations. • Optimum amplitude has been validated via experiments on 24′′size specimens. • The new concept increases resilience of lap-welded pipelines in geohazard areas. [ABSTRACT FROM AUTHOR]

One of the most effective nondestructive methods to estimate the buckling load of imperfection sensitive thin-walled structures is vibration correlation technique (VCT). Although this technique can determine the buckling load for several types of structures without reaching the instability point, it is still under development for composite sandwich plates and shells. In this paper, experimental and numerical verification of VCT approach are presented for the estimation of the buckling load of the composite sandwich plates with iso-grid cores loaded in compression. In the experimental section, four specimens are designed and fabricated using a new silicone rubber mold, and hand lay-up technique. The modal test is performed on the first specimen by exciting the sandwich plates using the modal hammer method in the different applied loads. Then, the variation of the natural frequency with the applied compressive load is recorded up to actual experimental buckling load. Besides, numerical models, including nonlinear effects, are created in full details to calculate the variation of the natural frequencies with the applied load, and to be compared with the experimental results. Finally, the buckling test is carried out on all specimens to validate the experimental and numerical results of VCT approach. The results demonstrate that the maximum difference between the predicted buckling load using the VCT approach on the experimental and numerical results with an experimental buckling load is less than 3%. Also, VCT provides a reliable estimate of buckling load when the composite sandwich plates with iso-grid cores have been loaded up to at least 67% of the experimental buckling load. • Experimental and numerical validation of VCT approach were presented for the estimation of the buckling load of the composite sandwich plates with iso-grid cores. • The modal analysis of the composite sandwich plates with iso-grid-cores was performed using the modal hammer method. • Finite element models, including nonlinear effects such as geometric and thickness imperfection, was performed. • The maximum difference between the predicted buckling load using the VCT approach on the experimental and numerical results with an experimental buckling load was less than 3%. • It was shown that VCT provides a reliable estimate of buckling load when the composite sandwich plates with iso-grid cores have been loaded up to at least 67% of the critical load. [ABSTRACT FROM AUTHOR]

This paper presents an analytical and numerical investigation of the relationship between the compressive load level and the natural frequency variation toward a vibration correlation technique for the buckling load calculation of imperfection-sensitive isotropic cylindrical shell structures. Firstly, a back-to-basic s study is proposed and the linear equation between the applied load and the square of the loaded natural frequency is revisited. Such review considers the Flügge-Lur'e-Byrne's linear shell theory for the free vibrations of an isotropic unstiffened cylindrical shell under uniform axial loading. The demonstrated linear equation is rearranged for expressing the square of the applied load as a quadratic function of the square of the loaded natural frequency. The suggested formulation provides the analytical support to a novel vibration correlation technique that has been empirically proposed and experimentally validated for unstiffened cylindrical shells. Aiming a numerical verification based on finite element models, two cylindrical shells are defined. At first, the critical buckling load and the fundamental natural frequency for different load levels are determined and compared to the analytical results for validation of the numerical models. The finite element models are extended considering geometric nonlinearities, more realistic boundary conditions and three magnitudes of a benchmark measured initial geometric imperfection. The numerical results are considered for analyzing the variation of the natural frequency in the surroundings of buckling and for verifying the vibration correlation technique. • The free vibration of an axially loaded simply supported cylinder is revisited to verify an existing VCT. • A new insight to define a VCT which does not depends on the similarities between buckling and vibration modes is proposed. • The capability of the VCT to provide conservative estimations is corroborated through detailed numerical models. [ABSTRACT FROM AUTHOR]

Abstract This paper presents the results of an experimental and numerical study of the behavior of circular hollow section (CHS) steel tubes strengthened by Aramid fiber-reinforced polymer (AFRP). The aramid fiber used for this experiment is available under the trade name of Kevlar 49. In this study, thin-walled circular steel tubes externally bonded with fiber in the hoop direction were tested under axial compression to examine the effects of the AFRP thickness, on their axial load carrying and shortening capacity. The three-dimensional finite element models (FEM) of AFRP strengthened circular hollow section (CHS) was developed using ANSYS Workbench Ver. 19.0 and ACP (ANSYS Composite Prep/Post) tool considering both geometric and material nonlinearities. The effects combined of AFRP damage and interlaminar failures for the bonded interface are modeled within FEM using "Hashin" failure criteria and Cohesive Zone Model (CZM), respectively, to provide an accurate simulation. The results involving the failure modes, load vs. axial shortening curve and ultimate load capacity, were obtained from the experimental and numerical simulation and compared for validation. Both the experimental and numerical results are consistent, demonstrating that AFRP external strengthening can considerably enhance the strength of steel tube columns by 96% for short tubes and 23% for long tubes using 3 mm thickness of AFRP. Highlights • Conducted an experimental study of AFRP strengthening circular hollow section columns with different wrapping parameters. • Developed and validated FE models to simulate AFRP strengthened short and long CHS columns. • Conducted a parametric study on the effect of AFRP and steel thickness and length of the columns on the axial capacity. • The strength and stiffness of the AFRP strengthened specimens significantly improved compared to the control specimens. [ABSTRACT FROM AUTHOR]

Abstract The round-ended concrete-filled steel tube (RCFST) column behaves favorable prospects in engineering application due to its advantages of aesthetical properties and structural efficiency. Nevertheless, relevant studies were commonly focused on the mechanical performance of RCFST stub column. This paper developed a numerical analysis method for predicting the structural behaviour and failure mechanism of thin-walled RCFST slender column under axial compression. The nonlinear finite element (FE) modelling was established on the basis of the equivalent constitutive model and was verified well by the existing experimental results. Following this, several crucial geometric and material parameters were designed to explore the influences on the strength, stiffness and ductility of axially loaded thin-walled RCFST slender column. The impacts of various parameters on second order effect and buckling reduction factor of RCFST slender column were also identified. Furthermore, the mechanical performance of thin-walled RCFST slender column was evaluated by means of the axial force versus mid-height deflection characteristic and the contact stress. The numerical analysis results indicated that the axial strength of thin-walled RCFST slender column was obviously heightened by increasing the strength of concrete and steel in addition to the cross-section area, while contrary results were discovered with the increase of the slenderness ratio and the diameter-to-thickness ratio. Lastly, design recommendations for the axially-loaded thin-walled RCFST slender column were presented by comparing the numerical and previous experimental data with design provisions in specifications EC4, ANSI/AISI 360-16 and GB 50936. Highlights • A numerical method for predicting the structural behaviour of axially-loaded thin-walled RCFST slender column was developed. • The performance of RCFST slender column was evaluated by strength, ductility, contact stress and buckling reduction factor. • Design recommendations for the axially-loaded thin-walled RCFST slender column were presented. [ABSTRACT FROM AUTHOR]

Abstract Increasing the development in industrial technology and need for energy absorption, lightweight and cost effective composite materials such as composite sandwich panels have been in the center of attention. In this paper energy absorption properties of proposed composite sandwich panels with different corrugated core geometries under quasi static out of plane loading conditions is experimentally investigated. Three different corrugated shapes, i.e. rectangular, trapezoidal and triangular fabricated with the same thickness are used. The specimens were subjected to three different quasi-static compression loading condition i.e. concentrated, linear and planar. The effect of the number of unit cells and corrugated core geometries in determining the overall deformation and local collapse behavior of the panels also investigated. Based on the comparative results, it is found that three unit cell rectangular corrugated geometry possessed the best performance than other types of corrugated core geometries. Moreover, through visual observation the damage mechanisms under loading conditions and subsequent failure modes are inspected. Plastic buckling of cell walls and foam densification identified as the initial failure modes and by continuing the loading, fiber breakage, localized delamination as well as debonding between the skins and the core were the main damage mechanisms in these corrugated systems. Highlights • Characterization the effects of different corrugated core on energy absorption of sandwich panels. • Damage mechanism identification of sandwich panels under compressive loading conditions. • Performance of woven glass fibers as corrugation elements for infilled sandwich panels. [ABSTRACT FROM AUTHOR]

Abstract Face-to-face built-up cold-formed steel channel sections are becoming increasingly popular for column members in cold-formed steel structures; its applications include cold-formed steel trusses, space frames and portal frames. In such an arrangement, the independent buckling of the members is resisted by intermediate fasteners. In the literature, no research is available for such face-to-face built-up cold-formed steel columns. The issue is addressed herein. This paper presents the results of 36 experimental tests, conducted on face-to-face built-up cold-formed steel channel-sections covering a wide range of slenderness from stub to slender columns. A nonlinear finite element model is then described that shows good agreement with the experimental results. The finite element model includes material non-linearity, initial imperfections and modelling of intermediate fasteners. Both finite element and experimental results are compared against the design strengths calculated in accordance with the American Iron and Steel Institute (AISI), Australian and New Zealand Standards (AS/NZS) and Eurocode (EN 1993-1-3). The verified finite element model is used for the purposes of a parametric study comprising 90 models. The effect of fastener spacing on the axial strength was investigated. From the results of experiments and finite element investigations, it is shown that the design in accordance with the AISI & AS/NZS and Eurocode (EN 1993-1-3) is generally conservative by around 15%, however, AISI & AS/NZS and Eurocode (EN 1993-1-3) can be un-conservative by 8% on average for face-to-face built-up columns failed through local buckling. Highlights • Experimental tests were conducted on face-to-face built-up CFS channel-sections. • Initial geometric imperfections were measured for all test specimens using a laser scanner. • Nonlinear finite element models were developed which includes material nonlinearity and initial imperfections. • The column strengths were compared against the design strengths calculated in accordance with AISI & AS/NZS and EN 1993-1-3. • The AISI & AS/NZS and EN 1993-1-3 design strengths are generally conservative by around 15% but un-conservative by 8% on average for columns failed through local buckling. [ABSTRACT FROM AUTHOR]

Abstract This paper presents the results of numerical and analytical studies to obtain ultimate strength enhancement coefficient (R e) equations for external-ring-stiffened circular hollow section (CHS) X-joints under axial compression. The FE modeling approach is validated by the results of axial compressive experiments conducted in the authors' previous research on six X-joints with and without stiffeners. In all, 160 unstiffened and ring-stiffened FE models of CHS X-joints subjected to brace axial compression were investigated. The effects of the brace-to-chord diameter ratio β , the ratio of chord diameter to twice the chord wall thickness γ , the stiffening ring width factor β r (i.e. 2 b r / d 0 where b r is the ring width and d 0 is the chord diameter), and the stiffening ring thickness factor τ r (i.e. t r / t 0 where t r is the stiffening ring thickness and t 0 is the chord wall thickness) on the structural behavior of external-ring-stiffened CHS X-joints were evaluated. Parametric analysis showed that the ultimate strength enhancement coefficient R e decreased with the increase in the diameter ratio between the brace and the chord β, but once β exceeded 0.4, the effect on R e was slight. Furthermore, the ratios of chord diameter to twice the chord wall thickness γ , the stiffening ring width factor β r , and the stiffening ring thickness factor τ r were all positively correlated with improvement in the ultimate strength of the external-ring-stiffened CHS X-joints. An analytical formula based on the yield volume model was derived to predict the ultimate strength enhancement of external-ring-stiffened X-joints. Highlights • Enhancement of ultimate strength by an external stiffening ring on CHS X-joints is clarified. • 160 FE models were analysed to investigate the effect of geometric parameters on ultimate strength. • The failure modes of ring-stiffened X-joints are clarified. • A formula is proposed to determine the ultimate strength enhancement coefficient of ring-stiffened CHS X-joints under axial compressive loading. [ABSTRACT FROM AUTHOR]

Abstract The compressive stress is remarkable in design of steel plate walls (SPWs) for high-rise buildings. Stiffeners are required to avoid the compressive buckling in service limit state. This paper first studies the elastic stability of horizontally stiffened steel plate walls (S-SPWs) in compression. The effect of stiffener torsional stiffness on elastic buckling stress is presented. Then the study extends to the elastic-plastic stability of imperfect S-SPWs. Comparing the elastic and elastic-plastic behaviour, the increased ultimate compressive strength is smaller than the increased elastic buckling stress due to the column type buckling behaviour of wide plate. Stiffener torsional stiffness can also increase the ultimate capacity. Formulas to predict the stiffness requirement on horizontal stiffeners are proposed based on the philosophy similar to the stiffness requirement on brace for columns in compression. With some minor modifications, the proposed formulas show good accuracy compared with numerical results. [ABSTRACT FROM AUTHOR]

Abstract This paper presents a refined model for local buckling of rectangular concrete-filled steel tubular (CFST) columns with binding bars under axial compression due to a deficiency in the previous model i.e. the influences of horizontal spacing and diameter of binding bars were not considered. The influences of longitudinal spacing, horizontal spacing and diameter of binding bars on the critical local buckling stress can be reasonably considered in the proposed model, which is applicable to both elasto-plastic phase and elastic phase. The refined model is verified against the experimental results, showing better agreement than the previous model. Then, the proposed model is employed to investigate the influences of longitudinal spacing, horizontal spacing, diameter of binding bars and cross-sectional aspect ratios on the critical local buckling stress. It is found that the critical local buckling stress increases considerably with the decrease of the spacing of binding bars. Furthermore, the influence of longitudinal spacing of binding bars on the critical local buckling stress is more significant than that of horizontal spacing. It is also found that the critical local buckling stress increase modestly with the increase of diameter of binding bars in the case of small spacing of binding bars. In addition, the cross-sectional aspect ratio have little influence on the critical local buckling stress, which can be ignored. Aiming at delaying the occurrence of local buckling of steel plates in rectangular CFST columns with binding bars, it is suggested that decreasing longitudinal spacing as an efficient measure has priority over other measures. Highlights • A refined model for local buckling of rectangular CFST columns with binding bars is proposed. • The influences of horizontal spacing and diameter of binding bars are considered in the model. • The previous model has been extended to elasto-plastic phase. [ABSTRACT FROM AUTHOR]

Abstract Concrete-filled steel tubular (CFST) structures have been widely applied in modern construction industry owing to the composite action between the concrete and the steel tube. The benefits of CFST structures can be further achieved if high-strength materials are used. However, when high-strength steel is applied to CFST structures, the thin-walled steel section may not develop its yield strength owing to the early crushing of the cover concrete. Therefore, this paper presents an experimental study on concrete-filled circular high-strength steel stub tube (CFHST) focusing on the effect of the diameter-to-thickness (D/t) ratio. Fifteen specimens were tested under axial compression, with D/t ratios ranging from 50 to 130. The effects of the D/t ratio on the failure mode, load-versus-deformation relationship, and axial compression strength were investigated. Test results showed that the CFHST with a large D/t ratio can still reach the plastic section design. The fibre element method proposed by Liang et al. was revised to predict the load-axial deformation curves and then validated by using the ultimate bearing strength of CFST columns from 215 collected data. Finally, the bearing capacity of CFHST columns was compared with the present design codes, namely, Eurocode 4, American Institute of Steel Construction standard (AISC 360-10), Architectural Institute of Japan (AIJ) standard, and the proposed model, to evaluate the feasibility of the current codes for predicting the axial compressive strength of CFHST under axial compression. Highlights • Tests on CFHST of five different D/t ratios are conducted. • A new hoop stress formula is proposed in the revised fibre element model. • 215 test data of CFST are collected to verify the fibre element model. • A comparison of the axial capacity between the test results and current codes is conducted. [ABSTRACT FROM AUTHOR]

Offshore steel tubular structures may be subjected to damage perforations by long-term operation in a corrosive environment, which reduces their structural strength. There is a lack of standards and procedures to quantify the loss of structural capacity in view of the damage dimension and geometrical and material characteristics of the tubular member. The present paper proposes the use of symbolic regression for assessing the remaining capacity of perforated steel tubular members from aged offshore units subjected to axial compressive forces. A Finite Element Analysis campaign was generated in combination with a full factorial design of experiments. Length-to-diameter, diameter-to-thickness and damage extension ratios have been addressed as potential preponderant factors for the experimental design. Results from numerical simulations were statistically evaluated and then symbolic regression was handled to generate an optimized expression by minimizing the worst error case between predicted and numerical results. Capacity responses from the generated expression lie close to the Finite Element Analysis and experimental results, suggesting that the proposed methodology can be alternatively employed to assess the remaining capacity of perforated steel tubular members subjected to axial compressive loads. [ABSTRACT FROM AUTHOR]

In the second part of this series paper, a high-fidelity finite element model was established first to systematically study the buckling behaviors of thin-walled cylindrical shell subjected to localized axial compression load. By comparing with the experimental results, the feasibility and accuracy of the present FE model were validated. Then, the buckling mechanism, failure mode and load carrying capacity of cylindrical shell under localized axial compression load were thoroughly discussed and elucidated. Finally, some key factors that affect the buckling behaviors of cylindrical shells were carefully investigated, including material yield strength, the amplitude and topography of initial geometric imperfections, and the location of localized axial compression load along shell circumference. Results indicated that the distribution scope of localized axial compression load, shell material yield strength and the amplitude of initial geometric imperfections play a dominant role in the buckling behaviors of cylindrical shell under localized axial compression loads. The experimental and numerical investigations carried out in this research work can be regarded as a systematic attempt to study the buckling problems of thin-walled cylindrical shell structures under the more complex and practical axial load conditions. The results and conclusions obtained from this paper can also provide some guides for the design and application of thin-walled cylindrical shell in actual engineering. • Buckling tests of 21 cylindrical shells under localized axial compression loads were performed. • FEA model to study buckling behaviors of cylindrical shell under localized axial loads was established. • Buckling mechanism and load carrying capacity of cylindrical shell under localized axial load were elaborated. • Effects of some key factors on the buckling behaviors of cylindrical shell were discussed. [ABSTRACT FROM AUTHOR]

This paper presents a detailed finite element (FE) analysis and design of cold-formed high strength steel (CFHSS) fire exposed X-joints with square and rectangular hollow section (SHS and RHS) brace and chord members. The nominal 0.2% proof stress of SHS and RHS members was 960 MPa. The static behaviour of SHS and RHS X-joints was numerically investigated corresponding to four post-fire temperatures, including 300°C, 550°C, 750°C and 900°C. The RHS X-joints were subjected to axial compression loads through brace members. The post-fire residual strengths of cold-formed S960 steel grade SHS and RHS X-joints were experimentally investigated by the authors. The test results were used to develop an accurate FE model. Through the validated FE model, a comprehensive FE parametric study comprising of 756 FE specimens was performed in this investigation. Overall, SHS and RHS X-joint specimens were failed by chord face failure, chord side wall failure and a combination of these two failure modes. The validity ranges of critical geometric parameters were extended beyond current limits mentioned in international codes and guides. Using the measured post-fire residual static material properties, nominal resistances were predicted from design rules given in Eurocode 3, CIDECT and literature. The residual joint strengths of test and FE specimens were compared with predicted nominal resistances. Generally, it has been shown that the existing design rules are quite conservative but unreliable. As a result, accurate and reliable design rules are proposed in this study. • Numerical investigation was performed for fire exposed cold-formed S960 steel RHS-to-RHS X-joints. • Parametric study comprised 756 FE specimens with post-fire temperatures ranging from 300°C to 900°C. • Chord face failure, chord side wall failure and a combination of these two failure modes were observed. • Residual strengths were compared with nominal resistances predicted from existing rules using post-fire material properties. • Current design rules are quite conservative but unreliable. Accurate and reliable design rules are proposed. [ABSTRACT FROM AUTHOR]

Thin-walled cylindrical shell structure not only shows the highly efficient load carrying capacity but also is vulnerable to buckling instability failure. In practical application, these structures are usually subjected to localized axial compression load, which is a common but complex non-uniform loading case. Until now, the buckling behaviors of thin-walled cylindrical shells under this kind of compression loading condition are still unclear, and there are also few relevant investigations. In order to fill this research gap, in the first part of this series paper the experimental studies on the buckling behaviors of thin-walled cylindrical shells under localized axial compression loads were performed for the first time. The buckling tests of twenty-one steel cylindrical shells were carried out in this paper and some key experimental details were given. The strain curve, axial load–displacement curve, critical buckling load as well as the buckling modes of cylindrical shells under localized axial compression load were systematically discussed. Test results indicated that the localized axial compression load plays a pivotal role in the buckling behaviors of thin-walled cylindrical shell, not matter from the point of view of load carrying capacity, load–displacement curve or buckling mode. The experimental results obtained from this work can be served as a benchmark for related research in this field of buckling analysis of thin-walled cylindrical shells. • Buckling tests of 21 cylindrical shells under localized axial compression loads were performed. • FEA model to study buckling behaviors of cylindrical shell under localized axial loads was established. • Buckling mechanism and load carrying capacity of cylindrical shell under localized axial load were elaborated. • Effects of some key factors on the buckling behaviors of cylindrical shell were discussed. [ABSTRACT FROM AUTHOR]

Beetle elytron plate (BEP) is a biomimetic sandwich structure inspired by the internal architecture of beetle elytra and characterisedby trabeculae in the core. This type of structure has been shown to possess superior mechanical properties to conventional sandwich plates; however, there are no studies that evaluate its structural bending resistance. This paper develops an analytical method to calculate the key component of bending resistance of BEPs: the elastic local buckling load of the compression skin. It assumes that the compression skin of BEPs is simply supported by the trabecular core. After eliminating local buckling in the edges of the compression skin outside the trabeculae, two buckling zones, depending on the ratio (η) of trabecular radius to the distance between two adjacent trabeculae, are identified. At low η values (η ≤ 0.25), elastic buckling occurs in the space of the compression skin surrounded by four adjacent trabeculae. Beyond the critical value of η (η >0.25), buckling occurs in the compression skin enclosed by individual trabecula. Guided by finite element simulation results, this paper identifies a new suite of deformation shape functions and derives local elastic buckling load for the compression skin according to the principle of minimal total potential energy. Afterwards, a convenient quadratic polynomial regression equation is proposed to modify the elastic buckling coefficient of the compression skin of equivalent conventional grid honeycomb sandwich plates, with the maximum difference between analytical calculation results and finite element simulation results being about 7%. • Finite element modelling of the behaviour of local buckling of the compression skin of beetle elytron plate. • Analytical derivation of local buckling load of the compression skin of beetle elytron plate. • Regression equation based on the compression skin of honeycomb sandwich structure. [ABSTRACT FROM AUTHOR]

The paper investigates the possibility to use the local plastic mechanisms to characterise the ultimate strength of short thin-walled cold-formed steel members subjected to eccentric compression about the minor axis. The research is based on previous studies and some new investigations of the authors. The plastic mechanisms for lipped channel members in eccentric compression about minor axis and the evolution of those mechanisms are analysed. Five different types of mechanisms for members in compression with different eccentricities are examined. [ABSTRACT FROM AUTHOR]

Carbon fiber reinforced polymer (CFRP) strengthened concrete-filled thin-walled steel tubular (CFST) column can improve its load carrying capacity and resolve local bugles or corrosion of thin-walled steel tube. However, little attention to CFRP strengthened CFST columns has been paid. This paper reported an experimental and numerical analysis on eccentric compressive behavior of circular CFST stub columns partially-wrapped by CFRP strips. A series of circular composite columns, including nine CFRP strengthened CFST stub columns and one bare CFST stub column, were tested subjected to eccentric compression. Moreover, a nonlinear finite element (FE) modeling in considering contact interactions of the composite columns was developed and verified by the test results in terms of eccentric load ( N ) - longitudinal shortening ( δ ) curves and failure patterns. Then, the influence of extensive parameters on the eccentric compressive behavior of CFRP strengthened circular CFST columns was also evaluated. Meanwhile, a simplified empirical method on the eccentrically-loaded stub composite columns was proposed on the basis of unified theory. The experimental and analytical data indicated that the eccentric compressive strength of CFRP strengthened circular CFST stub column was obviously influenced by load eccentricity, CFRP confinement factor, steel strength, core concrete strength and CFRP strength. The proposed simplified empirical formulas may provide a considerable approach for designing this type of composite structures in engineering practice. [ABSTRACT FROM AUTHOR]

The axial compressive behavior of carbon fiber reinforced polymer (CFRP)-confined post heated square concrete-filled steel tube (CFST) stub columns is experimentally investigated in this paper. Twenty CFRP-confined post heated square CFST stub columns and one CFST stub column left untreated at ambient temperature were axially tested. Subsequently, the failure mode, ultimate strength, load versus displacement curves, load versus strain distribution curves, initial stiffness, and ductility of the specimens were obtained and analyzed. The maximum temperature (600 ℃，800 ℃,1000 ℃, 1100 ℃) CFST stub columns exposed to and the number of the layer of CFRP sheets (zero, one, two, three and four) were considered as main parameters. The test results showed that, in general, the CFST stub columns wrapped with CFRP sheets shown a better mechanical behavior than those without CFRP sheets wrapping. Furthermore, the more the layers of CFRP sheets are, the higher the ultimate strength and initial stiffness of the CFST stub columns are. Based on the regression of the test data, the simplified formulae for ultimate strength of CFRP-confined post heated square CFST stub columns was proposed. Accuracy of the formulae was evaluated by comparison between the calculated and experimental results. [ABSTRACT FROM AUTHOR]