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Showing papers in "Thin-walled Structures in 2009"


Journal ArticleDOI
TL;DR: In this article, a nonlinear analysis and design of stiffened square stub columns under axial compression is performed using ABAQUS, a commercially available finite element (FE) program.
Abstract: Longitudinal stiffeners are effective in improving the overall performance of concrete-filled square or rectangular thin-walled steel tubular columns. This paper is concerned with the nonlinear analysis and design of stiffened square stub columns under axial compression. The nonlinear analysis is performed using ABAQUS, a commercially available finite element (FE) program. Close agreement is shown between the test and predicted results in terms of the load-deformation curves and ultimate strength. The column behaviour is investigated and discussed using this modelling. The limit of width-to-thickness ratio for the sub-panels and the rigidity requirement for the stiffeners is discussed. The feasibility using existing design codes to predict the load-carrying capacities of the stiffened composite columns is also dealt with in this paper.

228 citations


Journal ArticleDOI
TL;DR: Bambach et al. as mentioned in this paper described 20 experiments on short, axially compressed square hollow sections (SHS) cold-formed from G450 steel and strengthened with externally bonded carbon fiber reinforced polymer (CFRP).
Abstract: Carbon fibre reinforced polymer (CFRP) strengthening of structures has been gaining increasing interest, traditionally applied to concrete structures, and more recently applied to steel structures. This paper describes 20 experiments on short, axially compressed square hollow sections (SHS) cold-formed from G450 steel and strengthened with externally bonded CFRP. The SHS were fabricated by spot-welding and had plate width-to-thickness ratios between 42 and 120, resulting in plate slenderness ratios between 1.1 and 3.2. Two different matrix layouts of the CFRP were investigated. It is shown that the application of CFRP to slender sections delays local buckling and subsequently results in significant increases in elastic buckling stress, axial capacity and strength-to-weight ratio of the compression members. The experiments are an extension of a previous study [Bambach MR, Elchalakani M. Plastic mechanism analysis of steel SHS strengthened with CFRP under large axial deformation. Thin-Walled Structures 2007;45(2):159–70] in which 25 commercially produced SHS with plate slenderness values between 0.3 and 1.6 were strengthened with CFRP in the same manner. A design method is developed whereby the theoretical elastic buckling stress of the composite steel–CFRP sections is used to determine the axial capacity, and is shown to compare well with the 45 test results. A reliability analysis shows the method to be suitable for design.

165 citations


Journal ArticleDOI
TL;DR: In this article, closed-form expressions for approximating the influence of single or multiple holes on the critical elastic buckling stress of plates in bending or compression are developed, validated and summarized.
Abstract: Closed-form expressions for approximating the influence of single or multiple holes on the critical elastic buckling stress of plates in bending or compression are developed, validated and summarized. The expressions are applicable to plates simply supported on 4 sides and plates simply supported on 3 sides, commonly called stiffened and unstiffened elements in design. The expressions serve as a convenient alternative to shell finite element eigen-buckling analysis, which requires commercial software not typically accessible to the engineering design community. The forms of the expressions are founded on classical plate stability approximations, and are developed and validated with parametric studies employing shell finite elements. The finite element parametric studies demonstrate that holes may create unique buckling modes, and can either decrease or increase a plate's critical elastic buckling stress depending on the hole geometry and spacing. The validated closed-form expressions and their associated limits are intended to be general enough to accommodate the range of hole shapes, locations, and spacings common in engineering practice, while at the same time also defining regimes where explicit use of shell finite element analyses is still needed for adequate accuracy.

133 citations


Journal ArticleDOI
TL;DR: An innovative use of fiber-reinforced polymer (FRP) composite materials, to control the manifestation of local buckling in a flanged steel section, is proposed in this article.
Abstract: An innovative use of fiber-reinforced polymer (FRP) composite materials, to control the manifestation of local buckling in a flanged steel section, is proposed. In this method, the high stiffness and linear behavior of FRP materials are utilized to provide “bracing” against web or flange local buckling in a manner that strategically leverages the unique mechanical properties of each material in an efficient application domain. The experimental research reported is aimed at demonstrating the feasibility of using small quantities of FRP to provide cross-sectional stability through the bonding of FRP strips to flange elements of the cross-section, thereby increasing the critical load of the member; constraining plastic flow in the cross-sectional flange elements; and facilitating the manifestation of a well-formed and stable hysteretic response of the member under cyclic loading. The member becomes, in effect, an FRP stabilised steel section .

130 citations


Journal ArticleDOI
TL;DR: In this paper, an equivalent rectangular hollow sections (RHS) is proposed to derive the yield slenderness limit for EHS sections in axial compression, and an experimental investigation has also been carried out on the behaviour of concrete-filled EHS stub columns.
Abstract: Similar to concrete-filled tubular columns, void-filling of elliptical hollow sections (EHS) will produce increased strength, stiffness, energy absorption and fire resistance. Stub column tests on unfilled EHS were performed first. Discussions are made on the equivalent diameters in the literature for deriving the yield slenderness limit. An equivalent rectangular hollow sections (RHS) is proposed to derive such a limit for EHS sections in axial compression. An experimental investigation has also been carried out on the behaviour of concrete-filled EHS stub columns. Both normal concrete and self consolidating concrete (SCC) were used in the testing program. Different loading methods were investigated; e.g., loading through steel alone, loading through concrete alone and loading through the whole cross-section. This paper is based on experimental data on carbon steel EHS with an aspect ratio of 2, which is also the only product type currently produced. The load carrying capacity is compared with that predicted using EC4 and CAN/CSA-S16. Proposed design formulae are given.

123 citations


Journal ArticleDOI
TL;DR: In this paper, the results of the theoretical and finite element analyses of the lateral-torsional buckling of I-girders with corrugated webs under uniform bending were presented.
Abstract: This paper presents the results of the theoretical and finite element analyses of the lateral–torsional buckling of I-girders with corrugated webs under uniform bending. Even though lateral–torsional buckling could dominate the flexural strength of I-girders composed of thin-walled members, the torsional rigidity of the I-girder with corrugated webs is not yet sufficiently understood, for example, the method to evaluate the warping constant. In this paper, previous studies on the bending and torsional rigidities of the I-girder with corrugated webs are first discussed. Then, approximated methods for locating its shear center and calculating the warping constant are proposed. Using the proposed methods, the lateral–torsional buckling strength of I-girder with corrugated webs under uniform bending can be calculated easily. A series of finite element analyses are conducted and their results are compared with those of the proposed methods. Based on these comparisons, the proposed methods are successfully verified. Finally, the effects of the corrugation profiles of the web on the lateral–torsional buckling strength of the I-girder with corrugated webs are further discussed.

118 citations


Journal ArticleDOI
TL;DR: In this paper, an analytical formulation for the study of linearized local skin buckling load and nonlinear post-buckling behavior of isotropic and composite stiffened panels subjected to axial compression is presented.
Abstract: This paper presents an analytical formulation for the study of linearized local skin buckling load and nonlinear post-buckling behaviour of isotropic and composite stiffened panels subjected to axial compression. The skin is modelled as a thin plate introducing Donnell-Von Karman and Kirchhoff hypothesis and applying classical lamination theory, while the stiffeners are considered as torsion bars. The first part of the work deals with the study of linearized buckling load, and two analytical solutions are presented: one is based on Kantorovich method and the other one on Ritz method. The second part of the work regards the development of a semi-analytical formulation for the study of the post-buckling field, using a variational approach and applying Ritz method. Results are compared with a serie of finite element analysis. It is shown that analytical buckling loads differ from numerical ones for less than 12%, and that force–displacement curves are well predicted. A computer program called stiffened panels analysis (StiPAn) is developed on the basis of the presented formulation. It allows quick analysis of stiffened laminated panels and is suited to be used in optimization routines for preliminary design.

117 citations


Journal ArticleDOI
TL;DR: In this paper, over 150 experimental compression tests on closed-section, built-up members formed of intermediately welded c-channels were conducted, and these experimental values were compared to theoretical buckling capacities based on the Section C4.5 modified slenderness ratio.
Abstract: Cold-formed, built-up members are common compression elements in cold-formed steel joists, and these built-up members are susceptible to unique buckling behaviors. Built-up member design is addressed in Section C4.5 of the American Iron and Steel Institute 2001 Specification. Over 150 experimental compression tests on closed-section, built-up members formed of intermediately welded c-channels were conducted, and these experimental values were compared to theoretical buckling capacities based on the Section C4.5 modified slenderness ratio. Use of the modified slenderness ratio was exceedingly conservative. Capacities based on the unmodified slenderness ratio and C4.5 fastener and spacing provisions were consistently conservative.

116 citations


Journal ArticleDOI
TL;DR: In this paper, a simple analytical method is presented for estimating the fatigue crack growth and fatigue life of the CFRP repaired steel plates, and double-sided and single-sided repairs are investigated.
Abstract: Carbon fibre reinforced polymer (CFRP) composites have proven to be effective in enhancing the load-carrying capacity and in extending the fatigue life of structural steel elements. Most studies have relied extensively on experimental testing and numerical simulations. It is important to develop some efficient analytical methods for predicting the fatigue behaviour of the composites repaired structures. In this paper, a simple analytical method is presented for estimating the fatigue crack growth and fatigue life of the CFRP repaired steel plates. Two types of fibre sheets are studied. These are normal modulus (E=240 GPa) and high modulus CFRP (E=640 GPa) sheets. Both double-sided and single-sided repairs are investigated. The analytical models are verified by experimental results.

115 citations


Journal ArticleDOI
TL;DR: In this article, a mechanics model for CFDST beam-columns subjected to constant axial load and cyclically increasing flexural loading was developed for bridge and building construction and parametric analysis was performed on the behaviors of moment (M ) versus curvature ( φ ) response and lateral load (P ) versus lateral displacement ( Δ ) relationship for the composite columns.
Abstract: Concrete-filled double skin steel tubes (CFDST) have a great potential to be used in the construction of bridges and buildings. Limited information is available on the models for the moment ( M ) versus curvature ( φ ) response, and the lateral load ( P ) versus lateral displacement ( Δ ) relationship of these columns subjected to axial load and cyclically increasing flexural loading. A mechanics model is developed in this paper for CFDST beam-columns subjected to constant axial load and cyclically increasing flexural loading. The predicted cyclic responses for the composite columns are in good agreement with test results. Based on the theoretical model, parametric analysis was performed on the behaviours of moment ( M ) versus curvature ( φ ) response and lateral load ( P ) versus lateral displacement ( Δ ) relationship for the composite columns. Finally, simplified models for the moment ( M ) versus curvature ( φ ) response, and the lateral load ( P ) versus lateral displacement ( Δ ) relationship were suggested.

114 citations


Journal ArticleDOI
TL;DR: In this paper, an experimental study consisting of circular hollow section (CHS) beams reinforced by carbon fiber reinforced polymers (CFRP) was performed under pure bending and the results revealed that the strength of composite beams is influenced mainly by the amount of fibre reinforcement and the orientation of fibre skin.
Abstract: Particular structural forms such as circular tubular sections when under load may experience premature local buckling of the steel component, attributable to the thin-walled nature of the section. The use of high-strength advanced composite materials tends to accompany the minimum of structural weight, and is hence presently being assessed for effectiveness as supplementary external reinforcing materials. Composite beams of fibre-reinforced polymers (FRP) and steel, formed as tubular steel sections externally reinforced by thin-bonded carbon FRP (CFRP) sheets, exhibit many phenomena not found in conventional structural steel components, and these can have a marked bearing both on the behaviour of members composed of these materials and, by connotation, on the way in which such members are designed. The potential identification of CFRP reinforcement incorporated onto steel circular hollow section (CHS) beams has not been adequately explored, particularly in pure moment regions. This paper provides an experimental study consisting of CHS beams reinforced by CFRP sheets under pure bending. The role of the composite reinforcement is to interact with the enveloped steel component and to restrain the section to deform in a favourable fashion for strength enhancement. It is shown how these sections exploit the best attributes of both reinforcing fibres and steel, conferring greater strength to CHS beams made with thin-walled steel sections. The tests reveal that the strength of composite beams is influenced mainly by the amount of fibre reinforcement and the orientation of fibre skin. Also presented in this paper is an analytical method employing the modular ratio concept and considering the sectional slenderness limits of AS 4100 for evaluation of the strength of CFRP-reinforced CHS beams.

Journal ArticleDOI
TL;DR: In this article, the authors presented a buckling analysis of isotropic and orthotropic plates using the two variable refined plate theory, which takes account of transverse shear effects and parabolic distribution of the transversal shear strains through the thickness of the plate.
Abstract: Buckling analysis of isotropic and orthotropic plates using the two variable refined plate theory is presented in this paper. The theory takes account of transverse shear effects and parabolic distribution of the transverse shear strains through the thickness of the plate, hence it is unnecessary to use shear correction factors. Governing equations are derived from the principle of virtual displacements. The closed-form solution of a simply supported rectangular plate subjected to in-plane loading has been obtained by using the Navier method. Numerical results obtained by the present theory are compared with classical plate theory solutions, first-order shear deformable theory solutions, and available exact solutions in the literature. It can be concluded that the present theory, which does not require shear correction factor, is not only simple but also comparable to the first-order shear deformable theory.

Journal ArticleDOI
TL;DR: In this article, a front bumper beam made of three materials: aluminum, glass mat thermoplastic (GMT) and high-strength sheet molding compound (SMC) is studied by impact modelling to determine the deflection, impact force, stress distribution and energy-absorption behavior.
Abstract: In this paper, the most important parameters including material, thickness, shape and impact condition are studied for design and analysis of an automotive front bumper beam to improve the crashworthiness design in low-velocity impact. The simulation of original bumper under condition impact is according to the low-speed standard of automotives stated in E.C.E. United Nations Agreement, Regulation no. 42, 1994. The bumper beam analysis is accomplished for composite and aluminum material to compare the weight and impact behavior. The strength in elastic mode is investigated with energy absorption and impact force in maximum deflection situation. A good design of this part of automotives must prepare for the safety of passengers; meanwhile, should have low weight. Beside the role of safety, fuel efficiency and emission gas regulations are being more important in recent years that encourage manufacturer to reduce the weight of passenger cars. In this research, a front bumper beam made of three materials: aluminum, glass mat thermoplastic (GMT) and high-strength sheet molding compound (SMC) is studied by impact modelling to determine the deflection, impact force, stress distribution and energy-absorption behavior. The mentioned characteristics are compared to each other to find best choice of material, shape and thickness. The results show that a modified SMC bumper beam can minimize the bumper beam deflection, impact force and stress distribution and also maximize the elastic strain energy. In addition, the effect of passengers in the impact behavior is examined. The time history of the calculated parameters is showed in graphs for comparison. Furthermore, beside the above-mentioned benefits, some more advantages like easy manufacturing due to simple shape without-ribs, economical aspects by utilizing low-cost composite material and reducing weight with respect to others can be achieved by SMC material.

Journal ArticleDOI
TL;DR: In this article, the authors examined a composite damage constitutive model, MAT58, in LS-DYNA and its application for use in braided composite tube axial crush simulations.
Abstract: This paper examines a composite damage constitutive model, MAT58, in LS-DYNA and its application for use in braided composite tube axial crush simulations. The constitutive response of MAT58 was investigated using single element simulations. It was found that MAT58 reproduced the softening behavior of the braided composite under monotonic compressive loading, but failed in subsequent unloading and tensile loading cycles. A deficiency in the damage law in MAT58 was identified. Unloading and reloading a volume of material that had suffered some degree of damage was a part of the process with the progressing of crush zone during the axial crush of composite tubes. Consequently, this deficiency hinders the success of MAT58 in such applications. In tri-axial braided composite tube axial crush simulations, although the predicted initial peak forces were within 20% of the experimental values, the predictions for the specific energy absorption (SEA) values were consistently low, particularly for tubes without a plug as crush initiator. These discrepancies are attributable to the deficiency in the damage law in MAT58.

Journal ArticleDOI
TL;DR: In this article, a finite element analysis (FEA) model was used to study the flexural performance of circular concrete-filled thin-walled steel tubular (CFST) beam.
Abstract: This paper presents a finite element analysis (FEA) modeling to study the flexural performance of circular concrete-filled thin-walled steel tubular (CFST) beam. A set of test data was used to verify the FEA modeling; generally, good agreement was achieved. The FEA modeling was then used to investigate the stress and strain distributions across the composite section in the whole loading procedure. The composite action between the steel tube and its concrete core was analyzed. A strut–tie model was proposed for the load transfer mechanism of the circular composite member subjected to pure bending.

Journal ArticleDOI
TL;DR: In this paper, the use of composite materials for strengthening and repair of steel structures has attracted a great deal of attention during the last years and the results from various types of tests are summarized and discussed.
Abstract: The use of composite materials for strengthening and repair of steel structures has attracted a great deal of attention during the last years. In this paper, the research work conducted at Chalmers University of technology during the last five years in this field is reviewed. The results from various types of tests are summarized and discussed. Aspects related to stress analysis of adhesive joints, joint modification and failure modes in steel elements strengthened with bonded CFRP-laminates are discussed. Research needs within the studied problems are also highlighted.

Journal ArticleDOI
TL;DR: In this article, the authors developed useful insights on nonlinear finite element method application for ultimate limit state assessment of steel stiffened-plate structures subject to combined biaxial compression and lateral pressure actions.
Abstract: For design and strength assessment of various types of structures such as ships, offshore platforms, land-based structures, and aerospace structures, it has been realized that ultimate limit states (or ultimate strength) are much better basis than the allowable working stresses. Within the framework of ultimate limit state design and strength assessment, the primary task is to determine the level of imposed actions which causes the ultimate limit states. The aim of the present study is to develop some useful insights on nonlinear finite element method application for ultimate limit state assessment of steel stiffened-plate structures subject to combined biaxial compression and lateral pressure actions. As an illustrative example, outer bottom stiffened-plate structures of 100,000 ton class double-hull oil tankers are considered. The present study consists of two parts; Part I deals with plate elements surrounded by stiffeners or support members, and Part II treats stiffened panels, where some important factors of influence such as structural dimensions, initial imperfections, loading types and computational techniques in association with ultimate limit states are studied. For ultimate limit state computations, ANSYS nonlinear finite element method together with ALPS/ULSAP semi-analytical method is employed. Important insights developed from the present study are documented.

Journal ArticleDOI
Xiong Zhang1, Hoon Huh1
TL;DR: In this paper, the authors investigated the energy absorption characteristics of longitudinally grooved square tubes under axial compression by using explicit nonlinear finite element code LS-DYNA.
Abstract: This paper investigates the energy absorption characteristics of longitudinally grooved square tubes under axial compression by using explicit nonlinear finite element code LS-DYNA. The grooves are fabricated by stamping and the distributions of the effective plastic strain and the thickness variation from the stamping process are considered in the following crash analyses. From the simulation results, we find that when grooves are introduced on the sidewalls, the specific energy absorption of conventional tubes can be increased by up to 82.7% and the peak force can be reduced by up to 22.3%. The influences of several parameters, including the width of the tube, the length of the groove and the number of the grooves, are analyzed and the features of the deformation modes of grooved tubes are described. The introduction of groove is found to be an effective way to improve the crashworthiness of thin-walled structures.

Journal ArticleDOI
TL;DR: In this article, a generalised beam theory (GBT) formulation is proposed to perform first-order and buckling analyses of arbitrary thin-walled members, namely members with cross-sections that combine closed cells with open branches.
Abstract: This paper presents the derivation, validation and illustration of a generalised beam theory (GBT) formulation intended to perform first-order and buckling analyses of arbitrary thin-walled members, namely members with cross-sections that combine closed cells with open branches. Following a brief overview of the so-called “conventional GBT formulation”, as well as of the available extensions for different specific cross-section types, the paper addresses in detail the modifications that must be incorporated into the GBT cross-section analysis procedure to handle the simultaneous presence of closed cells and open branches. The proposed formulation is then employed to analyse the first-order and buckling behaviours of thin-walled members (mostly beams) with complex cross-sections. For validation purposes, the GBT-based numerical results are compared with values yielded by shell finite element and finite strip analyses.

Journal ArticleDOI
TL;DR: In this article, the authors investigated the strengthening of intact steel-concrete composite girders and the repair of notched steel beams, using carbon-fibre-reinforced polymer (CFRP) materials with Young's modulus varying from 150 to 400 GPa.
Abstract: This study investigates the strengthening of intact steel–concrete composite girders and the repair of notched steel beams, using carbon-fibre-reinforced polymer (CFRP) materials with Young's modulus varying from 150 to 400 GPa Three large-scale (6100 mm long) steel–concrete girders scaled down (4:1) with accurate proportional dimensions from a bridge, were tested Also, 15 small-scale (1000 mm long) W-sections with various levels and configurations of loss in the tension flange, induced by notching, were tested Flexural strength and stiffness of the composite girders were increased by 51% and 19%, respectively The outer CFRP short layer debonded prematurely, followed by concrete crushing No debonding occurred between the inner CFRP layer and steel Complete cutting of tension flanges in W-sections reduced their ultimate capacity and stiffness by 62% and 45%, respectively, whereas 50% loss of the flanges resulted in insignificant reductions In the former, the CFRP repair resulted in strength recoveries, up to 79% In the latter, insignificant gains were observed A model was developed for CFRP-strengthened composite girders, verified, and used in a parametric study It showed that the higher the CFRP modulus, the higher the gain in stiffness, but the lower the gain in flexural strength, due to the inherent reduction of tensile strength of CFRPs with higher modulus

Journal ArticleDOI
TL;DR: In this paper, the authors presented repair methods of fatigue cracks using CFRP strips using welded web gusset joints, which are the typical details in steel bridges, and confirmed the feasibility of the proposed technique as a useful repair method to improve fatigue life of steel structures.
Abstract: This paper presents repair methods of fatigue cracks using CFRP strips. In particular, the subject of repair is fatigue cracks initiated at welded web gusset joints, which are the typical details in steel bridges. Several repair methods were investigated experimentally focusing on weld details. In addition, more effective repair methods were also investigated using combination of CFRP strips and drill-holes. As a result, it was found that fatigue life after repair was significantly improved. Therefore, the authors confirmed the feasibility of the proposed technique as a useful repair method to improve fatigue life of steel structures.

Journal ArticleDOI
TL;DR: In this article, the vibrational analysis of single-walled carbon nanotubes (SWCNTs) is performed using a finite element method (FEM) using three-dimensional elastic beams and point masses and the beam element elastic properties are calculated by considering mechanical characteristics of the covalent bonds between the carbon atoms in the hexagonal lattice.
Abstract: Vibrational analysis of single-walled carbon nanotubes (SWCNTs) is performed using a finite element method (FEM). To this end, the vibrational behavior of bridge and cantilever SWCNTs with different side lengths and diameters is modeled by three-dimensional elastic beams and point masses. The beam element elastic properties are calculated by considering mechanical characteristics of the covalent bonds between the carbon atoms in the hexagonal lattice. The mass of each beam element is assumed as point masses at nodes coinciding with the carbon atoms. Implementing the atomistic simulation approach, the natural frequencies of zigzag and armchair SWCNTs are computed. It is observed that the findings are in good agreement with the molecular structural mechanics data available in the literature. Then, the computational results are adopted to develop a predictive equation to propose a quick tool for estimating natural frequencies of the SWCNTs with different boundary conditions and geometrical parameters.

Journal ArticleDOI
TL;DR: In this article, numerical simulations of thin-walled square hollow steel beams subjected to a uniform transverse blast load are presented to gain an insight into the temporal distribution of the global and local deformation and the adiabatic temperature rise in the beams.
Abstract: This paper presents the numerical simulations of thin-walled square hollow steel beams subjected to a uniform transverse blast load. The objectives of the numerical simulations were to gain an insight into the temporal distribution of the global and local deformation and the adiabatic temperature rise in the beams as a result of impulsive loading. Additionally, the finite element predictions using Ls-Dyna are compared to the experimentally observed global and local deformations. The full lengths of the beams were modelled using three material models based on the linear piecewise plasticity material model which incorporated strain hardening, with and without strain-rate hardening and with strain-rate hardening and temperature softening. The blast wave was simulated as a rectangular pressure pulse distributed over the top surface of the beams. Ls-Dyna and the material model used were found to predict the global and local deformation of the beams reasonably well. Incorporating strain-rate hardening was found to be important to be able to predict the global and local deformation of the beams. Thermal softening was found to play a small but not negligible role.

Journal ArticleDOI
TL;DR: In this paper, a numerical nonlinear large deflection elastoplastic finite element study is conducted to clarify how, when, and why plastic hinges that emerge in experimental tests actually form.
Abstract: A number of full-scale plate girders are modeled and analyzed to determine their shear failure mechanism characteristics. An objective of this numerical nonlinear large deflection elastoplastic finite element study is to clarify how, when, and why plastic hinges that emerge in experimental tests actually form. It is observed that shear-induced plastic hinges only develop in the end panels. These hinges are caused by the shear deformations near supports and not due to bending stresses arising from tension fields. Also, a comparison between the ultimate capacity of various plate girders and different codes and theories is presented. Finally, it is shown that simple shear panels, in the form of detached plates, do not accurately represent the failure mechanism of web plates.

Journal ArticleDOI
TL;DR: In this article, a rib-reinforced beam is compared with thin-walled hollow tube-like beams filled with and without foam materials (empty beam and foam-filled beam) in crashworthiness.
Abstract: In this paper, a rib-reinforced thin-walled hollow tube-like beam (named as rib-reinforced beam) is presented for potential application in vehicle bumper. Through numerical simulation of the bending behavior under impact loads, the rib-reinforced beam is compared with thin-walled hollow tube-like beams filled with and without foam materials (empty beam and foam-filled beam) in crashworthiness. The effects of the shape of the reinforced rib are investigated and the shape optimization design is performed for increasing energy absorption and reducing the initial peak force. A multi-objective crashworthiness optimization formulation including maximum energy absorption, maximum specific energy absorption and minimum initial peak force is constructed based on the ideal point method (IPM). The optimum configuration of the reinforced rib is given with a normalized cubic spline function. Numerical example results show that, compared with the empty and foam-filled beams with same weights, the optimized rib-reinforced beam has higher energy absorption performance and lower initial crash force. It is found that for the rib-reinforced beam little rumple is formed around the compressed indention, which helps to retard the collapse of the side wall and means more energy absorption.

Journal ArticleDOI
TL;DR: In this article, a closed-form solution to predict the moment-rotation response of a circular tube subjected to pure bending was developed based on the principle of energy rate conservation.
Abstract: Circular tubes have been widely used as structural members in many engineering applications. Therefore, its collapse behavior has been studied for many decades, focusing on its energy absorption characteristics and collapse mechanism. In order to predict the collapse behavior of members, one could rely on the use of finite element codes or experiments. These tools are helpful and have high accuracy but are costly and require extensive running time. Therefore, an approximate model of tubes collapse mechanism is an alternative especially for the early step of design. This paper is also aimed to develop a closed-form solution to predict the moment–rotation response of circular tube subjected to pure bending. The model was derived based on the principle of energy rate conservation. The collapse mechanism was divided into three phases. New analytical model of ovalisation plateau in phase 2 was derived to determine the ultimate moment. In phase 3, the Elchalakani et al. model [Int. J. Mech. Sci. 2002; 44:1117–1143] was developed to include the rate of energy dissipation on rolling hinge in the circumferential direction. The 3-D geometrical collapse mechanism was analyzed by adding the oblique hinge lines along the longitudinal tube within the length of the plastically deformed zone. Then, the rates of internal energy dissipation were calculated for each of the hinge lines which were defined in terms of velocity field. Inextensional deformation and perfect plastic material behavior were assumed in the derivation of deformation energy rate. In order to compare, the experiment was conducted with a number of tubes having various D/t ratios. Good agreement was found between the theoretical prediction and experimental results.

Journal ArticleDOI
TL;DR: In this paper, the authors describe eight tests carried out on thin-walled steel tube confined concrete (TWSTCC) column to reinforced concrete (RC) beam joints subjected to cyclic loading, where the column cross-sectional type and the level of axial load in the column were selected as test parameters.
Abstract: This paper describes eight tests carried out on thin-walled steel tube confined concrete (TWSTCC) column to reinforced concrete (RC) beam joints subjected to cyclic loading, where the column cross-sectional type and the level of axial load in the column were selected as test parameters. In addition, two concrete filled thin-walled steel tubular column to RC beam joints were also tested for comparison. Each TWSTCC joint specimen consisted of a TWSTCC column and a RC beam pass through the column to represent an interior joint in a building. The experimental results are analysed to evaluate the influences of different testing parameters on the performance of the beam-column joints. It was found that the TWSTCC joints show generally excellent seismic performance and is adoptable in practical engineering, particularly in earthquake zone.

Journal ArticleDOI
TL;DR: In this paper, the effects of the material grading index and the geometry of the rotating disk on the stress and displacement fields were investigated and the results were verified with the known results in the literature, which can be concluded that the gradation of the metal-ceramic components and the geometrical properties of the disk are significant parameters in the thermomechanical responses of FG disks.
Abstract: A theoretical solution for thermoelastic analysis of functionally graded (FG) rotating disk with variable thickness based on first-order shear deformation theory (FSDT) is presented. Material properties and disk thickness profile are assumed to be represented by power law distributions. A semi analytical solution for displacement field is given under two types of boundary conditions applied for solid and annular disks. The effects of the material grading index and the geometry of the disk on the stress and displacement fields are investigated. Mechanical responses homogeneous disks versus FG disks are compared and verified with the known results in the literature. It is seen that the transverse displacements in FG solid disks with roller support condition at the outer surface remain between the minimum displacement value for the full-ceramic disk and the maximum displacement value for the full-metal disk. It is found that the transverse displacements in FG mounted disks with free condition at outer surface may not lie in between the displacement values for full-metal and full-ceramic disks. It is observed that the absolute moment resultant for FG mounted disk with concave profile is lowest compared to the FG mounted disk with linear or convex profile. It can be concluded that the gradation of the metal–ceramic components and the geometry of the disk are significant parameters in the thermomechanical responses of FG disks.

Journal ArticleDOI
TL;DR: In this article, the necessary similarity conditions for free vibrations of orthogonally stiffened cylindrical shells are developed using the similitude theory, and different examples are solved to validate the scaling laws numerically and experimentally.
Abstract: In this paper, the necessary similarity conditions, or scaling laws, for free vibrations of orthogonally stiffened cylindrical shells are developed using the similitude theory. The Donnell-type nonlinear strain–displacement relations along with the smearing theory are used to model the structure. Then the principle of virtual work is used to analyze the free vibration of the stiffened shell. After non-dimensionalizing the derived formulations, the scaling laws are developed, using the similitude theory. Then, different examples are solved to validate the scaling laws numerically and experimentally. The obtained results show the effectiveness of the derived formulations.

Journal ArticleDOI
TL;DR: In this article, the authors present a procedure to determine an element-length dependent strain and stress relation until fracture that is suitable for implementation in finite element models. But this procedure is not suitable for non-linear numerical simulations.
Abstract: This paper presents a procedure to determine an element-length dependent strain and stress relation until fracture that is suitable for implementation in finite element models. This material relation is obtained experimentally with an optical measuring system. The strain until fracture is calculated from the measured surface displacements. The stress is derived from the measured force and the cross-sectional area in the necking region. Furthermore, because of the digital nature of the optical measurements, the strain reference length, being a function of the pixel size, is clearly defined. For the numerical simulation the finite element length is equal to this strain reference length. The overall procedure allows a precise numerical simulation of the tensile experiment until the point of fracture without curve fitting or an iterative procedure to adjust the material relation for the chosen mesh size. This precise material relation can improve non-linear numerical simulations.