bluuebunny/crossref_metadata_2025_split huggingface dataset:
04.12: Analysis of silo supporting ring beams: Resting on discrete supports
Authors: Zeybek Özer , Topkaya Cem , Rotter J. Michael 
Published: September 2017

ABSTRACTSilos in the form of a cylindrical metal shell are often supported on a ring beam which rests on discrete column supports. The function of the ring beam is twofold. First, it is required to carry circumferential forces to maintain equilibrium at the transition junction between the cylinder and hopper. Second, the ring beam plays an important role in redistributing the majority of the discrete forces from the column supports into a more uniform stress state in the cylindrical wall. The Eurocode EN 1993‐4‐1 [1] only provides design equations for stress resultants produced in the isolated ring beam under uniform transverse loading. This paper explores the extent to which a practical silo shell causes these stress resultants to be reduced when the ring beam has only practical stiffness.The behaviour of a ring beam which interacts with the silo shell is much more complex than that of an isolated ring beam. In traditional design treatments, it is assumed that the discrete support forces are redistributed entirely by the ring beam to provide circumferentially uniform axial membrane stresses in the silo shell. But this assumption is only even approximately valid if the ring beam is much stiffer than the silo shell [2]. Since the cylindrical shell is very stiff in its own plane, the ring beam that responds with both flexure and twisting must be remarkably stiff to be stiffer than the shell. A ring beam stiffness ratio was previously developed by the authors to find the requirement for the ring beam stiffness to meet this traditional role [2]. This paper presents a new study to explore the ring beam stress resultants when closed section ring beams of lower stiffness and practical dimensions are used. A finite element parametric study is undertaken to explore the stress resultants and displacements in more flexible ring beams connected to a silo shell. The results show that the level of reduction from the isolated ring beam values can be directly related to the ring beam to shell stiffness ratio.
04.16: Rethinking imperfections in tanks and silos
Authors: Knoedel Peter , Ummenhofer Thomas , Rotter J. Michael 
Published: September 2017

ABSTRACTA careful consideration of imperfections is critical to the design of shell structures to ensure that they are both adequately safe and economically built. Following the development of the Eurocode for shell structures EN 1993‐1‐6, the situation has considerably improved:
the extensive literature on the imperfection sensitivity of shells has been introduced into practical designs;
fabrication tolerance classes have been defined, which allow the designer to adjust his design to the professional efforts of the fabricator; and
numerical and experimental results have been matched by defining an axisymmetrical weld depression as a substitute imperfection in the recent amendment.
These advances seem to have established a very good position, and it might be thought that little more needs to be done. However, a closer look at some of the above items reveals the need to reconsider the management of imperfections, especially from the designers point of view. In this paper the authors attempt to make a first step to resolve the role of imperfections from different points of view. In addition, some unpublished results from researches at KIT are presented.
04.17: Cylindrical shell buckling under a hydraulic constraint: Numerical study
Authors: Sabau Gabriel , Koltsakis Efthymios , Lagerqvist Ove 
Published: September 2017

ABSTRACTSteel cylindrical shell structures are used in a large variety of civil engineering applications such as off‐ shore platforms, tanks, silos, wind turbine towers, etc. The local stability of such structures and their sensitivity to imperfections is a well‐known problem. In current engineering practice the design method is based on the selection of an imperfection class for the shell and subsequently calculating a reduction factor,χ, to the resistance of the shell. One such methodology is supplied by the EN1993‐1‐6; special conditions are given to pressurized tubes subjected to meridional compression.Past studies have focused on the stability of cylindrical shells with internal pressure. The stability problem of a long cylinder considering the internal pressure as a simple static load was addressed. Thus, the approaches considered the fluid as compressible.The purpose of the present work is to investigate numerically the potential benefit of using an incompressible fluid fully enclosed in a circular cylindrical shell. The constraint imposed by the presence of the liquid in the interior of a shell will be referred to as “hydraulic constraint”. As liquids are nearly incompressible, the buckling of a liquid‐filled shell has to satisfy the condition that the integral of all the displacements normal to the shell surface is equal to the volume variation of the contained liquid. The volume variation of the shell interior has to be equal to the dilation of the shell due to liquid pressure increments associated to the onset of geometrical instability. Additionally, the weight of the contained liquid causes additional circumferential tension in the cases of vertically placed cylinders.The methodology followed is the numerical analysis of cylindrical shells by means of the ABAQUS Finite Element code and a comparison with the methods given in the Eurocode.
05.05: A flexibility‐based element for second‐order inelastic analysis using plastic hinge method
Authors: Du Zuo‐Lei , Liu Yao‐Peng , Chan Siu‐Lai , Tan Wei‐Qi 
Published: September 2017

ABSTRACTIn the past decades, the stiffness‐based elements with plastic hinge method and the flexibility‐based elements with plastic zone method are widely used for second‐order inelastic analysis. The former emphasizes the computational efficiency with relatively less accurate structural responses while the later aims to precisely simulate the structural behaviour but normally needs more computer times. For the member under complex loads, several stiffness‐based elements are generally required to capture its plastic behaviour. In such case, one‐element‐per‐member for member initial imperfection required in second‐order direct analysis is violated. On the contrary, a flexibility‐based element with several integration points is sufficient for material yielding. However, the more integration points associated with fibre section the more computational efforts are needed. It is also noted that the conventional flexibility‐based type elements cannot meet the codified requirements of direct analysis due to lack of consideration of member initial imperfection. In this paper, a new flexibility‐based element equipped with plastic hinge method without huge computational time is proposed for second‐order inelastic analysis. This element is also able to take the member initial bowing into account. Thus, an innovative solution is proposed for routine design. Finally, several numerical examples are used to demonstrate the validity and accuracy of the proposed method.
05.07: Structural behaviour of simple steel beams subject to axial compression, biaxial bending moments and torsion
Authors: Walter Adrian , Herbersagen Julia , Winkler Rebekka , Knobloch Markus 
Published: September 2017

ABSTRACTEuropean design rules provide simplified design models for steel beams subjected to biaxial bending moments and torsion (e.g. Annex A of EN 1993‐6 [1]). However, these rules do not consider axial forces. This paper presents a combined experimental and numerical study on the structural member behaviour of simple steel beams under axial compression, biaxial bending and torsion. First, an experimental study performed at Ruhr‐Universität Bochum is presented. Secondly, a numerical model is developed and validated with the results of the tests. Next, a numerical parametric study analyses the influence of the cross‐section, member slenderness ratio and ratio of internal forces on the member stability behaviour. The paper uses the results of both the numerical simulations as well as the experimental investigations for reviewing the existing simplified structural models. Finally, the paper develops and proposes a simplified model for simple steel members subjected to combined axial compressive forces, biaxial moments and torsion.
05.12: Effect of initial imperfection on elasto‐plastic behavior of SHS columns under axial force with bending moment
Authors: Mitsui Kazuya , Sato Atsushi , Aoyama Masahiro 
Published: September 2017

ABSTRACTSteel products which have various characteristic (e.g. high ductility, high yield stress, low yield stress and high weldability) are used as main structures by diversification of demanded application, and technology for steel manufacturing has developed. Because steel square tubular member is processed by cold‐forming and welding in the process of manufacturing, residual stress will exist in the products. Moreover, due to the cold‐forming process, geometrical initial imperfection, i.e., global and local, will exist. These initial imperfection are still remained even so the technology for steel manufacturing is developed. However, effect of the initial imperfection on elasto‐plastic behaviour of square hollow section columns under compressive axial force with bending moment is not clarified. In this paper, firstly, the effect of individual initial imperfection (e.g. initial global imperfection, initial local imperfection or residual stress) on elasto‐plastic performance is investigated independently; comparison between the experimental results are shown. It is shown that initial local imperfection has a significant impact on elasto‐plastic performance. Secondly, the effect of composite initial imperfections is investigated. The amplitude of the local imperfection is the most influential initial imperfection on the deformation capacity of the column, and the deformation capacity decreased with an increase of the amplitude of local imperfection. Validation of the numerical simulation were also performed and recommend values of imperfections are shown.
05.13: Efficient static and dynamic analysis of steel frames by one‐element‐per‐member models
Authors: Liu Si‐Wei , Liu Yao‐Peng , Chen Liang , Chan Siu‐Lai 
Published: September 2017

ABSTRACTThis paper proposes an efficient numerical analysis technique for static and dynamic analysis of space steel frames by one‐element‐per‐member model, considering material and geometric nonlinearities including P‐Δ‐δ effects, large global deflections and member deformations. The curved arbitrarily‐located‐hinge (ALH) beam‐column element is developed for capturing members' behaviours and simulating initial imperfections. Unlike the conventional plastic hinge element requiring two and more elements to capture the locations of plastic hinge along member length, which causes certain difficulties to model member initial imperfections, one proposed element per member is sufficient. The plastic hinges are simulated as gradually softening springs and the corresponding formulae are presented. The additional degrees of freedom in the element are condensed so that it can be easily incorporated into the existing software with dramatic improvement on numerical efficiency and accuracy. The consistent element mass matrix is derived based on the Hermite interpolation function, and the Rayleigh damping model is adopted for representing the system viscosity. Verification examples are given to validate the present model in simulating inelastic yielding and dynamic behaviours of the steel frames and members under loads. One distinct feature of the research is to propose an effective analytical framework using high‐performance elements, dramatically improving the numerical efficiency and making the method being practical.
05.17: Modeling the stiffness reduction conditions of steel beam‐columns
Authors: Rosson Barry 
Published: September 2017

ABSTRACTThe stiffness reduction that results from yielding of the cross‐section due to major and minor axis bending under axial compression and tension conditions is studied in detail for compact wide‐flange sections with an ECCS residual stress distribution pattern. For a given moment (m = M/Mp), axial load (p = P/Py), and residual stress ratio (cr = σr\σy), the distribution of stresses throughout the cross‐section and associated reduced stiffness (τ = EIep/EI) are evaluated using a fiber element model with 2,046 elements. Using increments of m and p of 0.01, detailed three‐dimensional m‐p‐τ surface plots for a given wide‐flange section are used to discuss the various stress states of the cross‐section and associated reduced flexural stiffness. Equations are provided for the m and p conditions around the perimeter of the 3‐D surfaces and for the various conditions at which yielding initiates in the flanges and web. For minor axis bending, figures are provided on the progression through the various stress states as m is increased from the initial yield point up to the fully plastic state for the axial compression conditions of p = 0.2 and 0.75. The m‐p‐τ surface plots are used to develop material models for direct implementation in MASTAN2. To study the effects of simplifying the 3‐D surface plots using a linear variation of stiffness between the initial yield surface and fully plastic conditions, the El‐Zanaty portal frame is modeled using MASTAN2 with p = 0.4 and 0.6 to compare the maximum lateral load and deflection results with published results. Discussion and recommendations are provided regarding the development and use of the m‐p‐τ surface plots for research and design purposes.
05.23: Optimal prestressing of triple‐bay prestressed stayed columns
Authors: Yu Jialiang , Wadee M. Ahmer 
Published: September 2017

ABSTRACTA nonlinear finite element model of the triple‐bay prestressed stayed column is developed within the commercial software ABAQUS. A linearly obtained ‘optimal prestress’ that maximizes the critical buckling load is investigated since this quantity has been demonstrated in previous work on single‐bay prestressed columns to provide a lower bound to the actual maximum load carrying capacity when compared to results from physical experiments and nonlinear modelling. The ratio of the crossarm to column length, the diameter of the cable stays and the ratio of the prestressing force to the linear optimal prestress are varied. Measures for the relative cost of the main column and the stays are defined and it is determined that the true optimal prestress is generally higher than the linearly obtained quantity but by a reduced factor when compared to an equivalent study for the single‐bay column case.
05.24: New interaction formulae for sensitive structures to the second order effects
Authors: Mercier Charlotte , Khelil Abdelouahab , Pamies Alain 
Published: September 2017

ABSTRACTEurocode 3 Part 1‐1 [1] gives a method to calculate the design criterion of a structure without include the imperfection in the model structure. This criterion enables to take into account the imperfection mainly with the buckling coefficient χ. However, we can highlight that the results obtained with this criterion (interaction formulae for beam‐column) are overestimated compared to the results obtained when the imperfection where included in the model structure. This difference comes from the coefficient χ which is overestimated.In order to overcome this problem, a new coefficient definition has been established in order to take into account the imperfection in the calculation without include it in the model structure. This new coefficient enables to take into account the charge level of the structure. First, vertically loaded structures have been studied. Then the study is extended to the vertically and horizontally loaded structures. The study results are more close to the actual results. Thus, this new coefficient enables to substitute for the establishment of an initial imperfection both a safe and a reasonable assessment of stress rate.
05.27: Resistance of mono‐axially bent beams of welded I‐sections: FEM verification of Eurocode's buckling curve formulation
Authors: Giżejowski Marian Antoni , Szczerba Radosław Bronisław , Gajewski Marcin Daniel 
Published: September 2017

ABSTRACTPresent Eurocode's approach to design of steel I‐section beams is based on the analytical resistance evaluation yielding from the interaction resistance criteria established for beam‐columns that cover two design situations: a) the flexural in‐plane failure (second order biaxial bending and compression), and b) the flexural‐torsional out‐of‐plane failure (second order spatial bending, warping torsion and compression). The Eurocode's unified resistance ultimate limit state criteria of I‐sections are depended upon the technological aspects of steel section production via the buckling curve differentiation for the evaluation of reduction factors for buckling in compression and lateral‐torsional buckling in bending about the major axis. This paper attempts to verify the Eurocode's buckling resistance criteria in case of welded I‐section in mono‐axial bending on the basis of finite element simulations and on the separate inclusion of material and geometrical imperfections. The finite element shell model is utilized and built within the ABAQUS software. The Eurocode's resistance criteria are verified by results of FEM simulations in case of moment gradient loading conditions. Concluding remarks in relation to analytical formulations presented in Eurocode 3 are drawn.
05.29: Interaction curves for local and distortional buckling of polygonal tubes in combined torsion and axial loading
Authors: Rendall Morgan A. , Hancock Gregory J. , Rasmussen Kim J.R. 
Published: September 2017

ABSTRACTThis paper investigates the interaction of uniform axial loading (compressive or tensile) and uniform torsion on the linear elastic buckling behaviour of long tubes with regular convex polygonal cross‐sections. The analyses pertain to tubes of sufficient length such that the results are independent of end boundary conditions. Using the generalised constrained finite strip method (cFSM), pure local buckling is examined for triangular through octagonal tubes. The interaction curves for pure local buckling are akin to those previously generated from the exact finite strip method and a square and octagonal tube are analysed in‐depth to assess the changes in interaction behaviour as the number of sides in the section is increased. The pure distortional buckling behaviour is examined for pentagonal through octagonal tubes using recent developments in Generalised Beam Theory (GBT) and an almost linear interaction between torsion and compression is found, as has been noted previously for circular tubes. The distortional interaction curves are essentially identical for all analysed tubes.
05.35: Extended design method for in‐plane stability of haunched sway portal frames
Authors: van Hove B.W.E.M. (Dianne) , Snijder H.H. (Bert) , Hofmeyer Herm , Altinga Noud 
Published: September 2017

ABSTRACTIn current design rules the effect of a haunch on the sway in‐plane stability of a steel portal frame only takes into account the influence of the haunch dimensions on the beam‐to‐column connection strength and stiffness. The effect of the haunch dimensions on the beam behavior, and thus on the frame behavior, is not included. The paper describes the effect of this phenomenon by regarding current design methods and comparing these with analytical solutions. The validity of the methods is covered by numerical simulations.For a vertical beam loading, the larger the span of the portal frame, the higher the compressive force in the beam becomes. In addition, the longer the span of the frame, the smaller the critical buckling load of the beam becomes. This decreases the stability of the overall frame significantly. In fact, the compressive force in the beam of a portal frame has a significant effect on the additional stiffness the haunch provides to the column. Due to the adjusted center line of the haunch causing an eccentricity, an additional first order moment is generated. This additional internal moment reduces the additional stiffness the haunch provides. For some spans this may even cause the additional stiffness of the haunch to be negligible.The research has given more insight, also on the effect of the shift of the compressive force in the beam, which depends on the geometry of the haunch. The study resulted in two simple correction factors for the current design rules, where these correction factors cover amplification factors for the original stiffness of the beam. The factors depend on the kind of loading (point load or equally distributed load) and on the haunch to rafter ratio (with regard to the length of the haunch as well as with regard to the height of the haunch).
05.36: An efficient approach to limiting the elastic range in advanced analysis of steel structures via RPHM
Authors: Lemes Ígor José Mendes , Barros Rafael Cesário , Batelo Everton André Pimentel , da Mota Silveira Ricardo Azoubel 
Published: September 2017

ABSTRACTOver the years many research on the nonlinear behavior of steel structures has been made. The Refined Plastic Hinge Method (RPHM) is a fast and accurate alternative to simulate, in concentrated form, the plasticity of the structural systems materials. In recent studies, there was a loss of accuracy in the analysis of steel structures under minor axis bending, in the conventional method of RPHM where pseudo‐springs are used at the ends of the elements to simulate the flexural stiffness degradation. In this approach, the pseudo‐springs at the finite elements ends have infinite stiffness in elastic range, with gradual loss of stiffness in elastoplastic stage and a null stiffness in plastic range. For the methodology adjust to this issue, the fictitious springs were replaced by the tangent modulus of elasticity of the material and presented as a viable solution. In this paper, we propose the study of the interaction curves behavior for application in RPHM with pseudo‐springs, considering the bending around major and minor axes of inertia, with a greater focus to RPHM using the tangent Young's modulus. The Strain Compatibility Method (SCM) is used, which through a nonlinear procedure, the moment‐curvature relationship is defined allowing to obtain the exact point where the cross section starts the yield process. Thus, it is possible to trace the initial yield curve realistically minimizing simplifications. The residual stresses models of AISC‐LRFD e ECCS for I sections will be used. The results will be compared with numerical and experimental data available in the literature.
05.40: Warping constant equations for hot rolled steel channel sections
Authors: Zhang Ailin , Zhang Qingfang , Jiang Ziqin 
Published: September 2017

ABSTRACTThe warping constant is one of the most important section properties for the buckling behaviour of structural members. The formulas for section warping constants are usually based on the middle line mode, and the flange slopes as well as the flange‐to‐web fillets are neglected. In this paper, 32 standard C shapes from the AISC manual were used as examples. They are drawn in AUTOCAD according to their real dimensions, and then the files are imported into ANSYS to calculate the sections' properties. It is found that the warping constants listed in the AISC manual are overestimated by about 26%. Taking the flange slope into account, a new expression of the warping constant for C shapes is presented. After a simple modification, the overestimated margin can be limited to about 5% using this new equation.