scholarly journals GBT-Based Elastic-Plastic Post-Buckling Analysis of Stainless Steel Thin-Walled Members

2019 ◽  
Author(s):  
Miguel Abambres ◽  
Dinar Camotim ◽  
Nuno Silvestre
Keyword(s):  
Stainless Steel ◽  
Life Cycle Cost ◽  
Strain Curve ◽  
X Rays ◽  
Structural Behaviour ◽  
Elastic Plastic ◽  
Equilibrium Configurations ◽  
Non Linear ◽  
Thin Walled ◽  
Deformation Modes

When compared with carbon steel, stainless steel exhibits a more pronounced non-linearity and no well-defined yield plateau, as well as appealing features such as aesthetics, higher corrosion resistance and lower life cycle cost. Due to its considerably high ductility/strength and cost, stainless steel structural solutions tend to be adopted mostly for slender/light structures, thus rendering the assessment of their structural behaviour rather complex, chiefly because of the high susceptibility to instability phenomena. The first objective of this paper is to present the main concepts and procedures involved in the development of a geometrically and physically non-linear Generalised Beam Theory (GBT) formulation and numerical implementation (code), intended to analyse the behaviour and collapse of thin-walled members made of materials with a highly non-linear stress-strain curve (e.g., stainless steel or aluminium). The second objective is to validate and illustrate the application of the proposed GBT formulation, by comparing its results (equilibrium paths, ultimate loads, deformed configurations, displacement profiles and stress distributions) with those provided by shell finite element analyses of two lean duplex square hollow section (SHS) columns previously investigated, both experimentally and numerically, by Theofanous and Gardner [1]. The stainless steel material behaviour is modelled as non-linear isotropic and the GBT analysis includes initial geometrical imperfections, but neglects corner strength enhancements and membrane residual stresses. It is shown that the GBT unique modal nature makes it possible to acquire in-depth knowledge concerning the mechanics of the column behaviour, by providing “structural x-rays” of the (elastic or elastic-plastic) equilibrium configurations: modal participation diagrams showing the quantitative contributions of the global, local, warping shear and transverse extension deformation modes moreover, this feature makes it possible to exclude, from future similar GBT analyses, those deformation modes found to play a negligible role in the mechanics of the behaviour under scrutiny, thus further reducing the number of degrees of freedom involved in a GBT analysis, i.e., increasing its computational efficiency.

First and Second Order Elastoplastic Analyses of Thin-Walled Metal Members using Generalized Beam Theory

2018 ◽  
Author(s):  
Miguel Abambres
Keyword(s):  
Finite Element ◽  
Stainless Steel ◽  
Cross Section ◽  
Beam Theory ◽  
Second Order ◽  
Flow Rule ◽  
Non Linear ◽  
Thin Walled ◽  
Shell Finite Element ◽  
Generalized Beam Theory

Original Generalized Beam Theory (GBT) formulations for elastoplastic first and second order (postbuckling) analyses of thin-walled members are proposed, based on the J2 theory with associated flow rule, and valid for (i) arbitrary residual stress and geometric imperfection distributions, (ii) non-linear isotropic materials (e.g., carbon/stainless steel), and (iii) arbitrary deformation patterns (e.g., global, local, distortional, shear). The cross-section analysis is based on the formulation by Silva (2013), but adopts five types of nodal degrees of freedom (d.o.f.) – one of them (warping rotation) is an innovation of present work and allows the use of cubic polynomials (instead of linear functions) to approximate the warping profiles in each sub-plate. The formulations are validated by presenting various illustrative examples involving beams and columns characterized by several cross-section types (open, closed, (un) branched), materials (bi-linear or non-linear – e.g., stainless steel) and boundary conditions. The GBT results (equilibrium paths, stress/displacement distributions and collapse mechanisms) are validated by comparison with those obtained from shell finite element analyses. It is observed that the results are globally very similar with only 9% and 21% (1st and 2nd order) of the d.o.f. numbers required by the shell finite element models. Moreover, the GBT unique modal nature is highlighted by means of modal participation diagrams and amplitude functions, as well as analyses based on different deformation mode sets, providing an in-depth insight on the member behavioural mechanics in both elastic and inelastic regimes.

scholarly journals GBT-Based Structural Analysis of Elastic-Plastic Thin-Walled Members

2019 ◽  
Author(s):  
Miguel Abambres ◽  
Dinar Camotim ◽  
Nuno Silvestre
Keyword(s):  
Finite Element ◽  
Structural Response ◽  
Beam Theory ◽  
High Strength ◽  
Elastic Plastic ◽  
Collapse Mechanisms ◽  
Non Linear ◽  
Steel Grades ◽  
Thin Walled ◽  
Shell Finite Element

Structural systems made of high-strength and/or high-ductility metals are usually also rather slender, which means that their structural behavior and ultimate strength are often governed by a combination of plasticity and instability effects. Currently, the rigorous numerical analysis of such systems can only be achieved by resorting to complex and computationally costly shell finite element simulations. This work aims at supplying to designers/researchers an efficient and structurally clarifying alternative to assess the geometrically and/or materially non-linear behavior (up to and beyond the ultimate load) of prismatic thin-walled members, such as those built from cold-formed steel. The proposed approach is based on Generalized Beam Theory (GBT) and is suitable for members exhibiting arbitrary deformation patterns (e.g., global, local, distortional, shear) and made of non-linear isotropic materials (e.g., carbon/stainless steel grades or aluminum alloys). The paper begins by providing a critical overview of the physically and geometrically non-linear GBT formulation recently developed and validated by the authors (Abambres et al. 2012a), which is followed by the presentation and thorough discussion of several illustrative numerical results concerning the structural responses of 4 members (beams and columns) made of distinct (linear, bi-linear or highly non-linear) materials. The GBT results consist of equilibrium paths, modal participation diagrams and amplitude functions, stress contours, displacement profiles and collapse mechanisms some of them are compared with values obtained from ABAQUS shell finite element analyses. It is shown that the GBT modal nature makes it possible (i) to acquire in-depth knowledge on the member behavioral mechanics at any given equilibrium state (elastic or elastic-plastic), as well as (ii) to provide evidence of the GBT computational efficiency, which is achieved by excluding from the analyses all the deformation modes that do not play any role in a particular member structural response.

Non-linear delamination fracture analysis by using power-law hardening

2016 ◽  
Vol 12 (1) ◽  
pp. 80-92 ◽  
Author(s):  
Victor Iliev Rizov
Keyword(s):  
Power Law ◽  
Strain Curve ◽  
Fracture Analysis ◽  
Stress Strain Curve ◽  
Stress Strain ◽  
Content Type ◽  
Elastic Plastic ◽  
Linear Fracture ◽  
Delamination Fracture ◽  
Non Linear

Purpose – The purpose of this paper is to perform a theoretical analysis of non-linear delamination fracture in cantilever beam opened notch (CBON) configuration. It is assumed that the non-linear mechanical behavior of the CBON can be described by using a stress-strain curve with power-law hardening. Design/methodology/approach – The fracture analysis is carried-out by applying the integration contour independent J-integral. For this purpose, a model based on the technical beam theory is used. Equation is derived for determination of the CBON specimen curvature in elastic-plastic stage of deformation. The equation is solved by using the MatLab program system. Solutions of the J-integral are obtained at linear-elastic as well as elastic-plastic behavior of the CBON. The influence of the power-law exponent on the non-linear fracture is evaluated. Findings – The analysis reveals that the J-integral value increases when the exponent of the power-law increases. The solution obtained here is very useful for parametric analyses of the non-linear fracture behavior, since the simple formulas derived capture the essentials of the fracture response. Practical implications – Beside for parametric investigations, the solution obtained here can also be applied for calculating the critical J-integral value at non-linear behavior using experimentally determined critical fracture load at the onset of crack growth from the initial crack tip position in the CBON configuration. Originality/value – An analysis is performed of the non-linear fracture in the CBON configuration by applying the J-integral approach, assuming that the mechanical response can be modeled using a stress-strain curve with power-law hardening.

Delamination analysis of a layered elastic-plastic beam

2017 ◽  
Vol 8 (5) ◽  
pp. 516-529 ◽  
Author(s):  
Victor Rizov
Keyword(s):  
Fracture Behaviour ◽  
Strain Curve ◽  
Integral Approach ◽  
Stress Strain Curve ◽  
Stress Strain ◽  
Content Type ◽  
Elastic Plastic ◽  
Lap Shear ◽  
Delamination Fracture ◽  
Non Linear

Purpose The purpose of this paper is to perform a theoretical analysis of delamination fracture behaviour of the Crack Lap Shear layered beam configuration taking into account the material non-linearity. A delamination crack located arbitrarily along the beam height was considered in this study. Design/methodology/approach The beam mechanical behaviour was described by using the Ramberg-Osgood stress-strain relation. Fracture was analysed by applying the J-integral approach. Besides by using symmetric Ramberg-Osgood stress-strain curve, fracture was investigated also by Ramberg-Osgood stress-strain curve that is not symmetric with respect to tension and compression. The J-integral solutions were verified by performing elastic-plastic analyses of the strain energy release rate. Findings The effects of crack location and material properties on the non-linear fracture behaviour were evaluated. It was found that the material non-linearity leads to increase of the J-integral values. Therefore, the material non-linearity has to be taken into account in fracture mechanics based safety design of structural members composed by layered materials. The analytical solutions derived are very useful for parametric investigations of delamination fracture with considering the material non-linearity. The results obtained can be applied for optimisation of the beam structure with respect to fracture performance. Originality/value The present study contributes for the understanding of delamination fracture in layered beams that exhibit non-linear material behaviour.

scholarly journals OPTIMIZATION OF ELASTIC-PLASTIC GEOMETRICALLY NON‐LINEAR LIGHTWEIGHT STRUCTURES UNDER STIFFNESS AND STABILITY CONSTRAINTS

2004 ◽  
Vol 10 (2) ◽  
pp. 97-106
Author(s):  
Romanas Karkauskas
Keyword(s):  
Optimization Problem ◽  
Optimality Criteria ◽  
Structural Behaviour ◽  
Lightweight Structures ◽  
Elastic Plastic ◽  
Compression Members ◽  
Non Linear ◽  
Design Values ◽  
Nodal Displacements ◽  
Tension Members

An actual structural design, especially that of lightweight structures, must evaluate strength, stiffness and stability constraints. A designed structure must satisfy optimality criteria. One faces known difficulties when trying to implement several from above mentioned requirements into optimization problem for further successful numerical realisation. A method to formulate the optimization problem, incorporating all above described criterions, mathematical model and algorithm to solve it numerically, taking into account the geometrically non‐linear structural behaviour are presented for truss type structure. In each optimization cycle the member forces obtained in the previous optimization cycle via elastic‐plastic non‐linear analysis procedure are employed to obtain the new optimal design values. During the optimization procedures, the tension members are assumed to be loaded up to the yield limit, compression members are assumed to be stressed up to their critical limits, the nodal displacements are restricted to limited magnitudes in prescribed directions. Design examples are presented to demonstrate the application of the algorithm.

scholarly journals A Novel Approach to Perform the Identification of Cross-Section Deformation Modes for Thin-Walled Structures in the Framework of a Higher Order Beam Theory

2019 ◽  
Vol 9 (23) ◽  
pp. 5186
Author(s):  
Lei Zhang ◽  
Aimin Ji ◽  
Weidong Zhu
Keyword(s):  
Cross Section ◽  
Higher Order ◽  
Preliminary Deformation ◽  
Structural Behaviour ◽  
Order Model ◽  
Thin Walled Structures ◽  
Novel Approach ◽  
Generalized Eigenvectors ◽  
Thin Walled ◽  
Deformation Modes

This paper presents a novel approach to identify cross-section deformation modes for thin-walled structures by assembling preliminary deformation modes (PDM) considering their participation in free vibration modes. These PDM, defined over the cross-section through kinematic concepts, are integrated in the governing equations of a higher order model and then uncoupled in the form of generalized eigenvectors. The eigenvectors are deemed to inherit the attributes of structural behaviours and can serve as the basis to assemble PDM. Accordingly, a criterion was developed to handle the eigenvectors, pursuing (i) the clustering of PDM that participate in a same structural behaviour, (ii) the assignation of the corresponding weights that indicate their participation and (iii) the decomposition of an amplitude function when it is related to several structural behaviours. Moreover, a numbering system was proposed to hierarchically organize the deformation modes, which is conducive to a reduced higher order model. The main features of this approach are found in its ability to be performed in a more operational way and its nature to give deformation modes physical interpretation inherited from the dynamic behaviours. The versatility of the approach was validated through both numerical examples and comparisons with other theories.

scholarly journals Geometrically and Materially Non-Linear GBT Analysis of Tubular Thin-Walled Metal Members

2019 ◽  
Author(s):  
Miguel Abambres ◽  
Dinar Camotim ◽  
Nuno Silvestre
Keyword(s):  
Beam Theory ◽  
Finite Element Analyses ◽  
Collapse Mechanisms ◽  
Non Linear ◽  
Post Buckling ◽  
Linear Material ◽  
Thin Walled ◽  
Shell Finite Element ◽  
Deformation Modes ◽  
Generalised Beam Theory

After providing a brief overview of a recently developed and validated elastoplastic post-buckling Generalised Beam Theory (GBT) formulation, the paper presents and discusses illustrative numerical results concerning three tubular members exhibiting bi-linear and non-linear material behaviours. The GBT results consist of equilibrium paths, modal participation diagrams, stress contours, displacement profiles and collapse mechanisms, most of which are compared with values obtained from Abaqus shell finite element analyses. The GBT modal nature makes it possible to (i) acquire in-depth knowledge about the member behavioural mechanics at any given equilibrium state (elastic or elastic-plastic), as well as (ii) evidence the GBT computational efficiency (d.o.f. reduction of over 75%), partly due to the exclusion from the analyses of all deformation modes playing no role in a given member response.

scholarly journals Semi-Precast Segmental Bridge Construction Method: Experimental Investigation on the Shear Transfer in Longitudinal and Transverse Direction

2021 ◽  
Vol 11 (12) ◽  
pp. 5502
Author(s):  
Stephan Johann Fasching ◽  
Tobias Huber ◽  
Michael Rath ◽  
Johann Kollegger
Keyword(s):  
Finite Element ◽  
Deformation Behaviour ◽  
Lateral Force ◽  
Concrete Bridges ◽  
Structural Behaviour ◽  
Element Analysis ◽  
Linear Finite Element ◽  
Non Linear ◽  
Thin Walled ◽  
The Stability

Large span concrete bridges with a box-shaped girder are usually built from prefabricated concrete segments or by in-situ casting of the concrete on a scaffolding system. Both technologies have their advantages and drawbacks. Recently a new approach to the construction of such bridges which combines the advantages of both existing solutions was proposed at the TU Wien. This method uses the standard precast segmental erection methods with their high construction speed, but divides the segments into easily transportable pre-fabricated thin-walled elements to create new, lighter versions of the segments. Following the installation of these lightweight segments, they are strengthened with additional concrete in their final position in the superstructure. This paper focuses on the transmission of shear forces during construction stages. Firstly, on the level of individual segments, where rigid cross-frames are necessary to guarantee the stability of the segments and secondly, on the level of a bridge girder built from such segments, where new joint types must be developed to ensure the force transfer between the segments. Different options for the formation of cross-frames as well as shear tests on double walls and concrete panels with steel girders are shown. In this experimental series, different shear transmitting elements were compared to each other and to calculations with non-linear finite element analysis, showing that all the investigated solutions are suitable for use in thin-walled bridge segments. Several methods, including a new concept for joining thin-walled pre-fabricated elements, are described for the joints between the segments. Push-off tests with a constant lateral force were carried out to assess the shear strength and deformation behaviour. The main parameters were the joint type (wet joints: plain, grooved, keyed; dry joints), the grout type, and the lateral force level. The test results are presented and the structural behaviour is further analysed using non-linear finite-element simulations.

DURACORR

Alloy Digest ◽  
1997 ◽  
Vol 46 (5) ◽  
Keyword(s):  
Fracture Toughness ◽  
Stainless Steel ◽  
Corrosion Resistance ◽  
Life Cycle ◽  
Physical Properties ◽  
Tensile Properties ◽  
Life Cycle Cost ◽  
Low Cost ◽  
Bend Strength ◽  
Steel Company

Abstract Duracorr is low-cost, utilitarian 11% Cr stainless steel with more corrosion resistance and life-cycle cost advantages than weathering steels. The steel may be used where a combination of abrasion and corrosion resistance is required. This datasheet provides information on composition, physical properties, microstructure, hardness, tensile properties, and bend strength as well as fracture toughness. It also includes information on corrosion resistance as well as joining. Filing Code: SS-680. Producer or source: Lukens Steel Company.

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