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Showing papers in "Thin-walled Structures in 2015"


Journal ArticleDOI
TL;DR: In this paper, a group of multi-cell tubes with different cell numbers were comprehensively investigated under both axial and oblique loads, and the results showed that different loading angles have different requirements on cell allocation and optimizations of multiple load cases can yield better solutions in a weighted average fashion, whereas the optimization for separate single load cases (SLC) could result in inferior performance under other load cases.
Abstract: Multi-cell tubes have been drawn increasing attention for their excellent energy-absorbing ability. However, the effect of cell number and oblique loads on crashing behaviors has seldom been studied to date. In this paper, a group of multi-cell tubes with different cell numbers were comprehensively investigated under both axial and oblique loads. The finite element models were first established and then validated by experimental tests. The simulation results showed that the increase in cell number can be beneficial to the energy absorption ( EA ) but detrimental due to increase in peak force ( F max ) under axial load. When the oblique loads were taken into account, the tubes could undergo global bending, which is an inefficient deformation mode. By applying complex proportional assessment (COPRAS) method, the 7×7 tube was selected as the best based on multi-criteria under multiple loading angles. Then the Kriging modeling technique and multiobjective particle optimization (MOPSO) algorithm were integrated to address the optimization problems, where EA and F max were taken as objectives and tube sizes as design variables. The results demonstrated that different loading angles have different requirements on cell allocation and optimizations of multiple load cases (MLC) can yield better solutions in a weighted average fashion, whereas the optimization for separate single load cases (SLC) could result in inferior performance under other load cases.

216 citations


Journal ArticleDOI
TL;DR: In this article, a finite element (FE) model was developed using implicit FE code ANSYS to simulate the deformation behavior and energy absorption of circular tubes under lateral loading and validated using experimental techniques to ensure that they can predict the responses of circular tube with sufficient accuracy.
Abstract: This paper addresses the energy absorption behaviour and crashworthiness optimisation of short length circular tubes under quasi-static lateral loading. Finite element (FE) models were developed using implicit FE code ANSYS to simulate the deformation behaviour and energy absorption of circular tube under lateral loading. These FE models were validated using experimental techniques to ensure that they can predict the responses of circular tube with sufficient accuracy. Response surface methodology (RSM) for design of experiments (DOE) was used in conjunction with finite element modelling to evaluate systematically the effects of geometrical parameters on the energy absorption responses of laterally crushed circular tubes. Statistical software package, design-expert, was used to apply the response surface methodology (RSM). The energy absorbing responses (specific energy absorbing capacity ( SEA ) and collapse load ( F )) were modelled as functions of geometrical factors (tube diameter, tube thickness, and tube width). These developed functions allow predictions of the energy absorption response of laterally crushed tubes, based on their geometry parameters. Based on DOE results, parametric studies were conducted to generate design information on using the laterally crushed tubes in energy absorbing systems. Finally, the approach of multi-objective optimization design (MOD) was employed to find the optimal configuration of the proposed energy absorption structures. Design-expert software, which employs the desirability approach as optimization algorithm, was used for solving the MOD problem.

151 citations


Journal ArticleDOI
TL;DR: In this paper, a model of aluminum foam filled square tubes under axial impact loading is presented, where the foam-filled thin-walled square tubes are modeled as shell wherein, foam core is modeled by incorporating visco-elastic plastic foam model in Altair® RADIOSSTM.
Abstract: Deformation and energy absorption studies with single, double and multi-wall square and circular tube structure with and without aluminum foam core are carried out for assessing its effectiveness in crashworthiness under the identical test conditions. Modeling and numerical simulation of aluminum foam filled square tubes under axial impact loading is presented. The foam-filled thin-walled square tubes are modeled as shell wherein, foam core is modeled by incorporating visco-elastic plastic foam model in Altair® RADIOSSTM. It is observed that the multi-wall tube structure with foam core alters the deformation modes considerably and results in substantial increase in energy absorption capacity in comparison with the single and multi-wall tube without foam core. Moreover, the multi-wall tube foam filled structure shows mixed deformation modes due to the significant effect of stress wave propagation. This study will help automotive industry to design superior crashworthy components with multi-tube foam filled structures and will reduce the experimental trials by conducting the numerical simulations.

122 citations


Journal ArticleDOI
TL;DR: In this article, the authors present a procedure to perform generalized beam theory (GBT) cross-section analysis, which is able to handle arbitrary (flat-walled) crosssection shapes and provides a rational set of deformation modes, which are hierarchically organized into several families, each with well-defined structural/mechanical characteristics.
Abstract: When analysing the structural behaviour of a thin-walled member by means of Generalised Beam Theory (GBT) – a one-dimensional folded-plate theory expressing the member deformed configuration as a linear combination of cross-section deformation modes with amplitudes varying along its length – the performance of the so-called “cross-section analysis” is the key step. Indeed, it consists of determining the deformation modes and evaluating the corresponding modal mechanical properties. However, the available procedures to perform this task are strongly dependent on the cross-section geometry type, a feature precluding its general, efficient and systematic numerical implementation. In order to overcome this difficulty, this paper presents the development and illustrates the application of a novel procedure to perform “GBT cross-section analyses” that (i) is able to handle arbitrary (flat-walled) cross-section shapes, (ii) can be numerically implemented in a systematic and straightforward fashion, and (iii) provides a rational set of deformation modes, which are hierarchically organised into several families, each with well-defined structural/mechanical characteristics. Both the analytical derivations and the underlying mechanical reasoning are explained in detail, and the selected illustrative examples cover the various types of relevant cross-section geometries.

108 citations


Journal ArticleDOI
TL;DR: In this paper, an exact solution is proposed for the nonlinear forced vibration analysis of nanobeams made of functionally graded materials (FGMs) subjected to thermal environment including the effect of surface stress.
Abstract: In the present investigation, an exact solution is proposed for the nonlinear forced vibration analysis of nanobeams made of functionally graded materials (FGMs) subjected to thermal environment including the effect of surface stress. The material properties of functionally graded (FG) nanobeams vary through the thickness direction on the basis of a simple power law. The geometrically nonlinear beam model, taking into account the surface stress effect, is developed by implementing the Gurtin–Murdoch elasticity theory together with the classical Euler–Bernoulli beam theory and using a variational approach. Hamilton’s principle is utilized to obtain the nonlinear governing partial differential equation and corresponding boundary conditions. After that, the Galerkin technique is employed in order to convert the nonlinear partial differential equation into a set of nonlinear ordinary differential equations. This new set is then solved analytically based on the method of multiple scales which results in the frequency–response curves of FG nanobeams in the presence of surface stress effect. It is revealed that by increasing the beam thickness, the surface stress effect diminishes and the maximum amplitude of the stable response is shifted to the higher excitation frequencies.

105 citations


Journal ArticleDOI
TL;DR: In this paper, a finite element model was developed and verified against tests of cold-formed steel built-up compression members, in which the initial geometric imperfections and material properties of the test specimens were included.
Abstract: A built-up I-section with longitudinal stiffeners is expected to have better performance to resist against local and distortional buckling compared to conventional built-up I-section by simply connecting two plain channels back-to-back. This paper presents a non-linear finite element analysis to investigate the behaviour of cold-formed steel built-up open section columns with edge and web stiffeners. A finite element model was firstly developed and verified against tests of cold-formed steel built-up compression members, in which the initial geometric imperfections and material properties of the test specimens were included. Secondly, the verified finite element model was used for an extensive parametric study of fixed-ended cold-formed steel built-up open section columns. The parametric study was designed to investigate the effect of edge and web stiffeners in the built-up open sections. The finite element results together with the test results were compared with the design predictions calculated from the current design rules in the North American Specification and the Australian/New Zealand Standard. Furthermore, design rules of the current direct strength method were modified. It is shown that the design strengths predicted by the modified direct strength method are generally in good agreement with the ultimate loads of the built-up open section columns. In addition, the current design rules and the modified direct strength method were evaluated by reliability analysis.

99 citations


Journal ArticleDOI
TL;DR: In this paper, a foam-filled thin-wall tube with functionally lateral graded thickness (FLGT) was proposed to accommodate axial crushing and lateral bending in real-life crash components.
Abstract: Crash components in automobiles are probably subjected to multiple loading conditions in real life, such as axial crushing and lateral bending. Unlike most of the existing work that solely focuses on the pure axial crushing or lateral bending, this paper attempts to accommodate both by proposing a novel structure, namely foam-filled thin-wall tube with functionally lateral graded thickness (FLGT). From numerical study of FLGT structures, they are found to exhibit noticeable advantage over the corresponding traditional uniform thickness (UT) structures with the same weight under both axial crushing and lateral bending. Moreover, the gradient governing the varying thickness shows significant influence on the crashworthiness performance of FLGT. To seek for the optimal gradient, a multi-objective optimization is carried out using multi-objective particle swarm optimization (MOPSO) algorithm, where response surface models are established to formulate the objectives functions, i.e. specific energy absorption (SEA) and peak impact force ( F peak ). The optimization results show that the foam-filled structure with FLGT can produce more promising Pareto solutions than traditional UT counterparts. Therefore, the FLGT structure could have potential applications subjected to different loading conditions.

93 citations


Journal ArticleDOI
TL;DR: In this paper, the generalized differential quadrature method (GDQ) and shell theories of different order were used to study free vibrations of laminated cylinders of oval and elliptic cross-sections.
Abstract: We use the generalized differential quadrature method (GDQ) and shell theories of different order to study free vibrations of laminated cylinders of oval and elliptic cross-sections. In the GDQ method partial derivatives of a function at a point are expressed as weighted sums of values of the function at several neighboring points. Thus, strong forms of equations of motion are analyzed. It is found that the computed frequencies rapidly converge with an increase in the number of grid points along the oval or elliptic circumference defining the cross-section of the mid-surface of the cylinder. For a clamped-free elliptic cylinder the converged frequencies match well with the corresponding experimental ones available in the literature. Furthermore, the lowest ten frequencies computed with either an equivalent single layer theory or a layer wise theory of first order and using shear correction factor are accurate.

93 citations


Journal ArticleDOI
TL;DR: In this paper, the issue of buckling load determination in composite channel section beams subjected to pure bending and channel section columns subjected to uniform compression is considered, and some selected problems with determination of bucking load on the basis of the collected and processed experimental data are discussed.
Abstract: The issue of buckling load determination in composite channel section beams subjected to pure bending and channel section columns subjected to uniform compression is considered. Some selected problems with determination of buckling load on the basis of the collected and processed experimental data are discussed. The data necessary to determine buckling load (applied load and the corresponding displacement, strains at chosen points of beam-columns and displacements in three perpendicular directions of all visible points of the considered beam-columns) were collected with a strain gauge system, an Aramis® 3D optical system and a universal testing machine. Buckling load was determined by means of the following well-known methods: the mean strain method, the method of straight-lines intersection on the graph of load vs. mean strains, the curve inflection point method, the load-square of deflection curve method and Koiter’s method. All results were obtained during the experimental investigations and the numerical FEM analysis of the channel section profile made of a GFRP laminate with the symmetrical eight-layer arrangement [45/-45/90/0]s. The profiles under consideration were subjected to compression or pure bending (four-point bending test). The rules for each methods of buckling load determination are proposed on the basis of the obtained results.

92 citations


Journal ArticleDOI
TL;DR: In this paper, a multi-objective optimization of foam-filled tubular tubes under pure axial and oblique impact loadings is presented, and the optimal crash parameter solutions, namely the minimum peak crushing force and the maximum specific energy absorption, are constructed by the Non-dominated Sorting Genetic Algorithm-II and the Radial Basis Function.
Abstract: This paper presents the multi objective optimization of foam-filled tubular tubes under pure axial and oblique impact loadings. In this work, the double circular tubes, whose bottom is the boundary condition, while at the top, is the impacted rigid wall; with respect to the axis of the tubes. The optimal crash parameter solutions, namely the minimum peak crushing force and the maximum specific energy absorption, are constructed by the Non-dominated Sorting Genetic Algorithm-II and the Radial Basis Function. Different configurations of structures, such as empty empty double tube (EET), foam filled empty double tube (FET), and foam filled foam filled double tube (FFT), are identified for their crashworthiness performance indicators. The results show that the optimal foam filled foam filled tube (FFT) had better crashworthiness than the others under pure axial loading. However, the foam filled empty tube (FET) was the best choice for structures under an oblique loading.

86 citations


Journal ArticleDOI
TL;DR: In this article, a comparison between steel plate and stiffened panels subject to localised corrosion was performed, showing the structural element selection can strongly influence the accuracy of the estimated corrosion damage effect.
Abstract: This study concentrates on a comparison between steel plate and stiffened panels subject to localised corrosion. A finite element analysis is used to investigate the effect of random corrosion on the compressive strength capacity of marine structural units. Variables include the extent of corrosion; slenderness ratio and aspect ratio. A corrosion prediction model is incorporated to determine the thickness reduction with time. Corrosion-induced volume loss results in a greater reduction of ultimate strength for slender plates compared to stiffened panels, up to 45%, showing the structural element selection can strongly influence the accuracy of the estimated corrosion damage effect.

Journal ArticleDOI
TL;DR: In this paper, a comparative study on the crushing responses of aluminum foam-filled corrugated single and double-tubes with different corrugation lengths was performed on finite element software LS-DYNA at impact velocity of 16.7m/s (corresponding to 60m/h).
Abstract: In this paper, aluminum foam-filling method was applied to corrugated tubes numerically, offering a novel structure that may have excellent energy absorption capacity. The study aims to provide a comparative study on the crushing responses of aluminum foam-filled corrugated single- and double-tubes with different corrugation lengths. The effects of geometric parameters like radius and wall thickness of inner tube in double-tubes on the energy absorption were also discussed. Dynamic crushing simulations were performed on finite element software LS-DYNA at impact velocity of 16.7 m/s (corresponding to 60 km/h). The comparisons revealed that tubes with corrugations experienced progressive and concertina type of deformation and tubes with smaller corrugation length showed smooth force–displacement curve with low initial peak force. SEA of foam-filled corrugated double-tubes was found to be superior to foam-filled straight tubes.

Journal ArticleDOI
TL;DR: In this paper, the authors present a review of recent research on the strength, stability and vibration behaviour of liquid-containment shell structures, and traces the developments pertaining to the design of these facilities to withstand various loading and environmental effects such as liquid pressure, wind pressure, ground movement and thermal effects.
Abstract: In civil engineering, shell structures are widely used as liquid-containment vessels. Understanding how the shell responds to relevant loading conditions is important for the design of safe and economical liquid-containment shell structures. This paper reviews recent research on the strength, stability and vibration behaviour of liquid-containment shell structures, and traces the developments pertaining to the design of these facilities to withstand various loading and environmental effects such as liquid pressure, wind pressure, ground movement and thermal effects. Results of recent feasibility studies of non-conventional shell forms for liquid containment are also reported, and areas of focus for future research are suggested.

Journal ArticleDOI
Hanfeng Yin1, Youye Xiao1, Guilin Wen1, Qixiang Qing1, Yufeng Deng1 
TL;DR: In this paper, the performance of foam-filled multi-cell thin-walled structure (FMTSs) with different cross-sectional configurations under lateral crushing load conditions was investigated using nonlinear finite element method through LS-DYNA.
Abstract: Nowadays, foam-filled multi-cell thin-walled structure (FMTS) has been widely used in the field of automotive due to their extraordinary energy absorption capacity and light weight. In this study, nine kinds of FMTSs with different cross-sectional configurations under lateral crushing load conditions were investigated using nonlinear finite element method through LS-DYNA. The complex proportional assessment (COPRAS) method was used to make clear which kind of FMTSs has the most excellent crashworthiness. According to this method, it can be found that FMTSs with 2, 3 and 9 cells are the top-3 excellent structures in our considered cases. In order to improve the crashworthiness of the three FMTSs, they were optimized by metamodel-based multiobjective optimization method which was developed by employing polynomial regression (PR) metamodel and multiobjective particle swarm optimization (MOPSO) algorithm. In the optimization process, we aimed to achieve maximum value of specific energy absorption (SEA) and minimum value of maximum impact force (MIF). Based on the comparison of the Pareto fronts obtained by multiobjective optimization, we can find that FMTS with 9 cells (FTMT9) performs better than FMTSs with 2 and 3 cells. Thus, the optimal design of FMTS9 is exactly an excellent energy absorption candidate under lateral impact and can be used in the future vehicle body.

Journal ArticleDOI
TL;DR: In this paper, the shear performance of double-layer wallboard sheathed with gypsum wallboard (GWB), bolivian magnesium board (BMG) and calcium silicate board (CSB) was investigated.
Abstract: To satisfy the requirements of fire resistance and loading capacity of the walls in multi-story cold-formed steel (CFS) structures, shear walls sheathed with double-layer wallboards on both sides were proposed. Sheathing materials in these walls included gypsum wallboard (GWB), bolivian magnesium board (BMG) and calcium silicate board (CSB). Cyclic loading tests on six full-scale walls of this configuration were conducted, from which the shear performance of the walls could be obtained. Factors such as the sheathing material, aspect ratio, stud section and stud spacing were considered. Another experimental study on the shear behavior of the screw connections was also performed to explore the potential relationship between the walls and the screw connections in shear performance. The results showed that the peak strength of the walls sheathed with bolivian magnesium boards as the face layer wallboards significantly exceeded the nominal value of the current standard. However, for the walls sheathed with calcium silicate boards as the face layer wallboards, the tested walls exhibited brittleness damage with poor ductility after the peak strength. The equivalent-bracing model was used to calculate the lateral stiffness of the walls, based on which a series of screw connection deformation limits and shear-wall drift angle limits was suggested.

Journal ArticleDOI
TL;DR: In this paper, the authors proposed the bionic non-convex multi-corner column (BI-NCMC) with bulkheads, which is a column with the smallest number of bulkheads.
Abstract: Collapse analysis of the non-convex multi-corner thin-walled columns under axial loads illustrates that the non-compact expansion-contraction deformation mode of collapse may occur in some cases, which reduces greatly the energy absorption property of these structures. Inspired from the way by which the bamboo nodes and nodal diaphragms enhance the transverse strength of bamboo, the non-convex multi-corner thin-walled column is modified by adding bulkheads in the column for improving the energy absorption property, and a new excellent energy absorption structure named as the bionic non-convex multi-corner column (BI-NCMC) is proposed in this article, which is a non-convex multi-corner thin-walled column with bulkheads. The energy absorption of BI-NCMC has been investigated numerically. A progressive deformation mode has been achieved and this structure shows a higher energy absorption than a similar column without the bulkheads. The role of the bulkheads is to change the deformation mode from an expansion-contraction mode to a progressive mode, while the bulkheads themselves absorb little energy. The influences of parameters in the energy absorption of BI-NCMC are analyzed. It was found that the column with highest energy absorption efficiency is the one with the smallest number of bulkheads while still maintaining the progressive deformation mode.

Journal ArticleDOI
TL;DR: In this article, a multi-cornered thin-walled sections were designed for axial collapse with the objective of maximizing specific energy absorption and minimizing peak to mean force ratio by seeking for the optimal design of these components.
Abstract: Plastic deformation of structures absorbs substantial kinetic energy when impact occurs. Therefore, energy-absorbing components have been extensively used in structural designs to intentionally absorb a large portion of crash energy. On the other hand, high peak crushing force, especially with regard to mean crushing force, may lead to a certain extent and indicate the risk of structural integrity. Thus, maximizing energy absorption and minimizing peak to mean force ratio by seeking for the optimal design of these components are of great significance. Along with this analysis, the collapse behavior of square, hexagonal, and octagonal cross-sections as the baseline for designing a newly introduced 12-edge section for stable collapse with high energy absorption capacity was characterized. Inherent dissipation of the energy from severe deformations at the corners of a section under axial collapse formed the basis of this study, in which multi-cornered thin-walled sections was focused on. Sampling designs of the sections using design of experiments (DOE) based on Taguchi method along with CAE simulations was performed to evaluate the responses over a range of steels grades starting from low end mild steels to high end strength. The optimization process with the target of maximizing both specific energy absorption (SEA) and crush force efficiency (CFE), as the ratio of mean crushing load to peak load, was carried out by nonlinear finite element analysis through LS-DYNA. Based on single-objective and multi-objective optimizations, it was found that octagonal and 12-edge sections had the best crashworthiness performance in terms of maximum SEA and CFE.

Journal ArticleDOI
TL;DR: In this article, a composite energy-absorbing structure for used in subway vehicles and investigates its collision performance through experiments and numerical simulations is proposed, and the results showed that the proposed structure provides a controllable crashing pattern that maximizes energy absorption and minimizes the peak forces during a collision.
Abstract: This study proposes a composite energy-absorbing structure for used in subway vehicles and investigates its collision performance through experiments and numerical simulations. The structure is described in detail and primarily consists of a front-end plate; square, thin-walled diaphragm; aluminum honeycomb structure; rear-end plate; and guide rail. In this study, a finite element (FE) model of the composite energy-absorbing structure was created and validated by experimental data. Based on the validated FE model of the composite energy-absorbing structure, the influence of the tube thickness and honeycomb material parameters on the crashworthiness of the composite energy-absorbing structure was analyzed in an LS-DYNA simulation environment. The results showed that the proposed structure provides a controllable crashing pattern that maximizes energy absorption and minimizes the peak forces during a collision. The tube thickness and honeycomb parameters affect the energy absorption of the composite structure. The results also indicated that as the thickness or honeycomb yield strength increase, the initial peak force and average crashing force increase, whereas the energy absorption does not follow the same trend.

Journal ArticleDOI
Xiaonong Guo1, Zhe Xiong1, Yongfeng Luo1, Liqiu Qiu1, Jia Liu1 
TL;DR: In this paper, the failure modes of the AAG joints are summarized in terms of their collapse phenomena and the stress distributions of the plates are discussed based on the measured strain, and the primary characteristics of the M-φ curves of the Gusset joints are obtained.
Abstract: Aluminium alloy gusset (AAG) joints are typical semi-rigid joints widely used in single-layer reticulated shells. Despite the semi-rigid behaviour of the AAG joints, structural analyses still show that dangerous situations can occur. To study the semi-rigid performance of the AAG joints, experiments on fourteen AAG joints are conducted. Initially, the failure modes of the AAG joints are summarised in terms of their collapse phenomena and the stress distributions of the plates are discussed based on the measured strain. Subsequently, the primary characteristics of the M-φ curves of the AAG joints are obtained. The bending stiffness properties of AAG joints are also investigated. The experimental results indicate the following: (1) the primary failure modes include member rupture, member buckling, block tearing of the top plates and local buckling in the bottom plates; (2) the moment-rotation relationship of the AAG joints exhibits a significant inelastic response; and (3) as the thickness of the gusset plate increases, the initial stiffness of the joint increases.

Journal ArticleDOI
TL;DR: In this paper, the effects of diameter and wall-thickness of bitubal circular energy absorbers and the interaction between two tubes on the crashworthiness parameters are investigated in detail.
Abstract: In this article, bitubal circular energy absorbers consist of two AL-6063-O tubes with unequal diameters placed coaxially and compressed under quasi-static axial load are studied experimentally. The effects of diameter and wall-thickness of each tube and the interaction between two tubes on the crashworthiness parameters are investigated in detail. In order to reduce the high value of peak load induced in the bitubal absorbers, two worthwhile solutions are proposed. The first one is to use two tubes with different lengths and the other one is to cut groove at the end portion of one of the tubes.

Journal ArticleDOI
TL;DR: In this article, a batch of T-shaped concrete-filled steel tubular (CFST) columns, T-shape steel tube confined concrete (STCC) columns and T reinforced concrete (RC) counterparts were tested subjected to concentric compressive load or eccentric compressive loads.
Abstract: In this paper, a batch of T-shaped concrete-filled steel tubular (CFST) columns, T-shaped steel tube confined concrete (STCC) columns and T-shaped reinforced concrete (RC) counterparts were tested subjected to concentric compressive load or eccentric compressive load. The battlement-shaped bar and tensile bar were developed as stiffeners to delay local buckling in tube wall. The stiffening mechanism, the failure modes of concrete and steel tubes, the strength and ductility of specimens were investigated in detail during the experimental research. A numerical modeling program was developed and verified against the experimental data. The numerical program, which incorporates the effect of the stiffeners on postponing local buckling of the tube and the confinement of the tube on concrete core, was used to carry out comprehensive parametric analysis of influencing factors on the structural behavior of T-shaped CFST columns.

Journal ArticleDOI
TL;DR: In this article, a comparative study on the crashworthiness of different functionally-graded thin-wall tubes under multiple loading angles, which include hollow uniform thickness, hollow functionally graded thickness (H-FGT), foam-filled uniform thickness (F-UT), and foam-filled functional graded thickness(FGT) configurations, is provided.
Abstract: This paper provides a comparative study on the crashworthiness of different functionally-graded thin-wall tubes under multiple loading angles, which include hollow uniform thickness (H-UT), hollow functionally graded thickness (H-FGT), foam-filled uniform thickness (F-UT) and foam-filled functionally graded thickness (F-FGT) configurations. First, finite element analyses of these differently graded circular tubes reveal that the F-FGT tube has the best crashworthiness under multiple loading angles. Second, parametric study on the F-FGT tube indicates that the thickness gradient and variation range significantly influence its crashworthiness. Third, the Non-dominated Sorting Genetic Algorithm (NSGA-II) is used to optimize the F-FGT tube, in which the optimal thickness variation is sought for maximizing specific energy absorption (SEA) and minimizing initial peak force (IPF) under multiple loading angles. The optimized F-FGT tube exhibits better crashworthiness than other three equivalent tube configurations, indicating that the F-FGT tube can be a potential energy absorber when oblique impact loading is inevitable.

Journal ArticleDOI
TL;DR: In this paper, the authors analyzed the squared plan-form single-layer structures, examining the influence of joint-rigidity on the mechanical performances of the structures, and found that the behavior determined using the finite element analysis (FEA) models correlates well with the experimentally observed behavior for the single layer structures with semi-rigid joints.
Abstract: Most existing studies on single-layer spatial structures with semi-rigid joints were focused on spherical domes. The present paper analyzed the squared plan-form single-layer structures, examining the influence of joint-rigidity on the mechanical performances of the structures. An experiment has been conducted on a 5×6 m single-layer cylindrical reticulated shell with semi-rigid bolt-ball joints. The mechanical performance of the latticed shell is investigated in detail. Finite element analysis (FEA) model of the latticed shell is established taking material and geometric nonlinearities into account. The results show that the behavior determined using the FEA models correlates well with the experimentally observed behavior for the single-layer structures with semi-rigid joints.

Journal ArticleDOI
TL;DR: In this article, the analytical and numerical studies of elastic buckling of a three-layered beam with metal foam core were conducted in ANSYS environment, where finite elements analysis has been performed using a linear buckling model.
Abstract: This paper deals with the analytical and numerical studies of elastic buckling of a three-layered beam with metal foam core. Mechanical properties of the core are variable along the z -axis. There are two schemes of displacement of the faces and core of the beam: a broken line hypothesis and a non-linear hypothesis. The mathematical models for both types of displacements are presented. The governing differential equations of the sandwich beam are derived. Numerical analysis of sandwich beams is conducted in ANSYS environment. The finite elements analysis has been performed using a linear elastic buckling model. The analysis with constant and variable Young׳s modulus of the core of the beam is carried out. The values of the critical load obtained by the analytical and numerical (FEM) methods are compared.

Journal ArticleDOI
TL;DR: In this paper, the effect of flange corrosion on axial capacity of steel bridge piles was investigated and a total of 13 H-shaped short columns were tested under monotonic axial load.
Abstract: To investigate the effect of corrosion on the axial capacity of steel bridge piles, a total of 13 H-shaped short columns were tested under monotonic axial load. The columns were machined to simulate different degrees and patterns of corrosion. The remaining axial capacity of the deteriorated members was assessed. To simulate the corrosion, webs and flanges were milled near the mid-height of the columns to reduce their thicknesses. The experimental results were compared to the axial capacities predicted by the design provisions of the American Institute of Steel Construction (AISC), American Association of State Highway and Transportation Officials (AASHTO), and American Iron and Steel Institute (AISI). The results of this study indicate that the degree of flange corrosion is the single factor that has the most significant effect on the column capacity. Other factors, including unsymmetry of the corrosion pattern or reduction of the flange width had a minor influence on the capacity. The results also indicate that, among the design methods considered, the effective width method recommended by AISI provides the best prediction of the capacity of severely deteriorated steel columns.

Journal ArticleDOI
TL;DR: In this article, a new strategy has been proposed to improve energy absorption efficiency of thin-walled columns by introducing extra stable corners in the cross-section, and several profiles of multi-corner thin-wall columns obtained through this strategy were presented and their crashworthiness capacities under axial crush loading were investigated analytically, experimentally, and numerically.
Abstract: Crash energy management in frontal crumple zone of the automotive body is one of the key elements for the design of automotive structure. Improving energy absorption characteristics reduces the magnitude of forces transferred to the occupant compartments. Here, a new strategy has been proposed to improve energy absorption efficiency of thin-walled columns by introducing extra stable corners in the cross-section. Several profiles of multi-corner thin-walled columns obtained through this strategy were presented and their crashworthiness capacities under axial crush loading were investigated analytically, experimentally, and numerically. First, explicit formulations for predicting the mean crushing force of multi-corner thin-walled columns were derived using the theory of super folding element (SFE). Predicted results of these formulations showed a good agreement with the results of quasi-static experiments and CAE simulations, which were performed by explicit non-linear finite element code through LS-DYNA. Based on this agreement, other significant crashworthiness assessment parameters were then investigated experimentally and numerically. Newly introduced 12-edge section with high energy absorption capacity was developed and its dominance was established through the responses in quasi-static experiments and CAE simulations. Finally, the foundational dominance of the 12-edge section was extended to the dynamic environment through a full vehicle crash test simulation to evaluate overall reduction in crashworthiness parameters which reflected occupant safety. Interestingly, in the case of using 12-edge section as crush absorbers, specific energy absorption (SEA), dash intrusion and maximum occupant’s chest deceleration showed significant improvement, compared to the baseline design which used a rectangular section.

Journal ArticleDOI
TL;DR: In this paper, the effects of two openings on the structural behavior of SPSWs were studied experimentally, and the experimental results were utilized to compare the ultimate shear strength, stiffness and energy absorption of specimens; to evaluate the performance of central, lateral, top and bottom panels; and to investigate the effect of distance between the openings and the columns on the formation of plastic hinges on the column flanges.
Abstract: One of the most important advantages of steel plate shear wall (SPSW) is to create openings with different sizes and arbitrary locations on the infill plate depending on their application. In this research, the effects of two openings on the structural behavior of SPSWs were studied experimentally. Experimental testing was performed on three one-third scaled single-story SPSW specimens with two rectangular openings under quasi-static cyclic loading. The differences between the three perforated experimental specimens were the interval between two openings and their closeness to the frame columns. The structural parameters of perforated specimens were compared to the similar specimen without any opening. The experimental results were utilized (a) to compare the ultimate shear strength, stiffness and energy absorption of specimens; (b) to evaluate the performance of central, lateral, top and bottom panels; (c) to investigate the effect of distance between the openings and the columns on the formation of plastic hinges on the column flanges; (d) to study the behavior of stiffeners around the openings. Test results showed that the ultimate shear strength, stiffness and energy absorption were the same in all three perforated specimens and the interval between the two openings had no effect on these values. Moreover, existence of openings will lead to reduction in values of structural parameters.

Journal ArticleDOI
TL;DR: In this article, an analytical solution for free vibration analysis of a functionally graded (FG) plate integrated with piezoelectric layers using four-variable refined plate theory is presented.
Abstract: This study presents an analytical solution for free vibration analysis of a functionally graded (FG) plate integrated with piezoelectric layers using four-variable refined plate theory. Equations of motion for simply supported rectangular plates are derived using Hamilton׳s principle and Maxwell׳s equation, and Navier method is employed for solution of equations. The numerical results are presented for isotropic, transversely isotropic and FG plates integrated with piezoelectric layers. The obtained natural frequencies for different examples are compared with the results of other common plate theories. The results demonstrate the simplicity, accuracy and efficiency of presented formulation in vibration analysis of investigated problems.

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TL;DR: In this article, the effects of the radius-thickness ratio, wavelength, and amplitude of corrugated tubes under an axial impact were determined using the LS-DYNA.
Abstract: Corrugated tubes with sinusoidal patterns were studied to improve the energy absorption properties of traditional circular tubes and reduce the initial peak force. The effects of the radius-thickness ratio, wavelength, and amplitude of corrugated tubes under an axial impact were determined using the LS-DYNA. The numerical simulations show that tube deformation can be classified into three crushed modes, namely, dynamic asymptotic buckling, dynamic plastic buckling, and transition buckling. The theoretical equation for dynamic plastic buckling was developed to predict the impact force using certain assumptions. The theoretical prediction results are consistent with the findings of the numerical simulations.

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TL;DR: In this paper, an investigation into the material response and local buckling behaviour of ferritic stainless steel structural cross-sections is presented, with particular attention given to the strain hardening characteristics and ductility.
Abstract: An investigation into the material response and local buckling behaviour of ferritic stainless steel structural cross-sections is presented in this paper. Particular attention is given to the strain hardening characteristics and ductility since these differ most markedly from the more common austenitic and duplex stainless steel grades. Based on collated stress-strain data on ferritic stainless steel, key aspects of the material model given in Annex C of EN 1993-1-4 [1] were evaluated and found to require adjustment. Proposed modifications are presented herein. The local buckling behaviour of ferritic stainless steel sections in compression and bending was examined numerically, using the finite element (FE) package ABAQUS. The studied section types were cold-formed square hollow sections (SHS), rectangular hollow sections (RHS) and channels, as well as welded I-sections. The models were first validated against experimental data collected from the literature, after which parametric studies were performed to generate data over a wide range of section geometries and slendernesses. The obtained numerical results, together with existing experimental data from the literature were used to assess the applicability of the slenderness limits and effective width formulae set out in EN 1993-1-4 [1] to ferritic stainless steel sections. The comparisons of the generated FE results for ferritic stainless steel with the design provisions of EN 1993-1-4 [1] , highlighted, in line with other stainless steel grades, the inherent conservatism associated with the use of the 0.2% proof stress as the limiting design stress. To overcome this, the continuous strength method (CSM) was developed as an alternative design approach to exploit the deformation capacity and strain hardening potential of stocky cross-sections. An extension of the method to ferritic stainless steels, including the specification of a revised strain hardening slope for the CSM material model, is proposed herein. Comparisons with test and FE data showed that the CSM predictions are more accurate and consistent than existing provisions thus leading to significant material savings and hence more efficient structural design.