Search

In this paper, a two-step free-form shape optimization methodology is presented for designing the optimal shapes of shell structures concerning stiffness maximization problem subject to a volume constraint. With this methodology, the optimization design problem of a shell structure is divided into two steps which consist a surface optimization step and a boundary optimization step. The shape sensitivities, called shape gradient function, are theoretically derived for both steps using the Lagrange multiplier method and the formula of the material derivative. The optimal shape is determined by applying the derived each shape gradient function on a design surface or boundaries to thegradient method. By the two-step free-form optimization, a smooth optimal shell with free-form surface and boundaries can be obtained to be a weight reduced form with high stiffness. Several calculated examples are presented to verify the validity and practical utility of the proposed methodology. [ABSTRACT FROM AUTHOR]

Up to now modules of parabolic trough collectors are usually made from steel frames carrying curved mirror elements. With these, the crucial disadvantage is the separation between supporting structure and reflecting surface. Here, the independent parts are merged to a very thin and light-weight but solid concrete shell having a highly precise inner surface that serves as substrate for mirror elements. Since concrete is originally very brittle and weak in tension, a special high-strength concrete with remarkable tensile strength is developed. Based on numerical analyses employing linear elastic material behaviour and limiting stresses below the tensile strength, two alternative module candidates have been designed with geometries close to already existent modules. Their design accounts for operation states by means of analytically and experimentally derived actions and constraints as well as time-dependent material effects. A first prototype on novel concrete supports demonstrates general feasibility. Highly accurate surfaces of the concrete shell, having a few centimetres of thickness only, prove structural stiffness and full optical efficiency in tests employing digital close range photogrammetry and analytically derived precision rates based on the surface slope error. [ABSTRACT FROM AUTHOR]

In this paper, the structural response of steel tubular wind turbine towers with various design configurations is analysed using FEM modelling. Towers of various heights between 50 and 250 m are considered and investigated with three different design options as follows: (i) thick walled tower with internal horizontal stiffening rings, (ii) thick walled tower without stiffening rings and (iii) thin walled tower with stiffening rings. Based on this analysis, weight reduction ratios are examined in relation to the horizontal sway and von Mises stress increase ratios in order to identify a more efficient design approach between reducing the wall thickness and adopting internal stiffeners. All studied design solutions satisfy the strength and serviceability requirements as specified by the design codes of practice. In the final part of paper, the dynamic characteristics of these three types of towers have been examined to obtain the natural frequencies and mode shapes. The studied model ignored the mass of nacelle-rotor system and the wind turbines, namely, only the isolated tower was included. Furthermore, the recommendations to avoid resonance for each height case are proposed. [ABSTRACT FROM AUTHOR]

Copyright of Architectus is the property of Oficyna Wydawnicza Politechniki Wroclawskiej and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

• Global imperfection involves deviation of the actual central axis from nominal axis and ovalization of the tank circumference. • Local imperfections can be more critical than the combination of global and local imperfections. • Field-measured imperfection amplitudes might exceed tolerance, but its shape has a significant impact on buckling capacity. • Buckling capacity of steel conical tanks is more sensitive to local imperfections compared to other imperfection components. Geometric imperfections caused by fabrication and welding reduce the buckling capacity of steel conical tanks. Few studies have considered field-measured geometric imperfections in such type of shell structures. This study carries out elastoplastic finite element analyses (FEA) to evaluate the buckling capacity of a full-scale stiffened conical steel water tank by considering its imperfections extracted from high-resolution laser scan data. Both global and local imperfections are obtained by comparing the laser scan data with the nominal tank geometry. The global imperfection involves deviation of the actual central axis of the tank from its nominal axis and ovalization of the tank circumference, whereas the local imperfection involves local fluctuations of the tank geometry around the circumference at a given elevation. The FEA is conducted using the commercial package ANSYS where both geometric and material nonlinearities are considered in the analysis. A four-node shell element with a six degrees of freedom per node is utilized in the model. The analysis results shed light on the shapes and magnitudes of global and local imperfections in an existing stiffened steel conical tank and their impact on the buckling capacity of the tank. Furthermore, the adequacy of imperfection tolerances recommended in widely used design standards for steel tanks are examined and compared with those extracted from the field measurements. The analysis results suggest that the local imperfections can be more critical than the combination of global and local imperfections in terms of the buckling capacity of the conical steel tank. [ABSTRACT FROM AUTHOR]

• Physics-Informed Neural Networks are presented for analyzing composite structures. • Extreme Learning is proposed for fast training of the network. • Subdomain decomposition allows assemblies of shell elements to be modeled. • Parametric studies illustrate the effect of network architectures and hyperparameters. • Improved effiency is achieved with respect to Gradient-Based Learning. This paper presents a novel approach for solving direct problems in linear elasticity involving plate and shell structures. The method relies upon a combination of Physics-Informed Neural Networks and Extreme Learning Machine. A subdomain decomposition method is proposed as a viable mean for studying structures composed by multiple plate/shell elements, as well as improving the solution in domains composed by one single element. Sensitivity studies are presented to gather insight into the effects of different network configurations and sets of hyperparameters. Within the framework presented here, direct problems can be solved with or without available sampled data. In addition, the approach can be extended to the solution of inverse problems. The results are compared with exact elasticity solutions and finite element calculations, illustrating the potential of the approach as an effective mean for addressing a wide class of problems in structural mechanics. [ABSTRACT FROM AUTHOR]

The effect of a static preload on the non-linear vibration behaviour of laminated anisotropic shells is studied. Starting point of the analysis is a perturbation approach developed earlier to analyse the non-linear vibration behaviour of imperfect general structures under static preloading. This method is based on a perturbation expansion for both the frequency parameter and the dependent variables, and can be used to study the effects of geometric imperfections, a static fundamental state, and a non-trivial static state on the linearised and non-linear vibrations of cylindrical shells. The theory has been incorporated within a semi-analytical framework, based on Donnell-type governing equations. The approach is applied in the non-linear vibration analysis of laminated, anisotropic cylindrical shells. Special characteristics of the non-linear free vibration behaviour of statically, axially loaded cylindrical shells are shown for a specific composite shell. Internal resonances corresponding to interactions between first order modes and second order modes are found in the analysis. Novel aspect of the current work is that these phenomena are considered within a framework in which effects of various types of boundary conditions, including the effect of non-linear static state deformation due to the application of the static load, are accurately taken into account. [ABSTRACT FROM AUTHOR]

The objective of this paper is to present an extension of the Lagrangian Smoothed Particle Hydrodynamics (SPH) method to solve three-dimensional shell-like structures undergoing large deformations. The present method is an enhancement of the classical stabilized SPH commonly used for 3D continua, by introducing a Reissner-Mindlin shell formulation, allowing the modeling of moderately thin structure using only one layer of particles in the shell mid-surface. The proposed Shell-based SPH method is efficient and very fast compared to the classical continuum SPH method. The Total Lagrangian Formulation valid for large deformations is adopted using a strong formulation of the differential equilibrium equations based on the principle of collocation. The resulting non-linear dynamic problem is solved incrementally using the explicit time integration scheme, suited to highly dynamic applications. To validate the reliability and accuracy of the proposed Shell-based SPH method in solving shell-like structure problems, several numerical applications including geometrically non-linear behavior are performed and the results are compared with analytical solutions when available and also with numerical reference solutions available in the literature or obtained using the Finite Element method by means of ABAQUS© commercial software. [ABSTRACT FROM AUTHOR]

Truncated conical vessels are commonly used as liquid containers in elevated tanks. Despite the widespread use of this type of structure worldwide, no direct code provisions are currently available covering its seismic analysis and design. The purpose of the current study is to assess the importance of considering the vertical component of ground accelerations when analyzing and designing this type of water-storage structure. The study is conducted using an equivalent mechanical model that estimates the normal forces that develop in the tank walls when subjected to vertical excitation. In addition, a three-dimensional finite element model has been developed by modeling the walls of the tank using shell elements. The finite element model has been employed to predict maximum membrane and overall meridional stresses due to both hydrodynamic and hydrostatic pressure distributions. Comparisons have been conducted to assess the significance of considering vertical excitation and to identify the magnification in meridional stresses due to bending effects associated with support conditions and large deformations. [ABSTRACT FROM AUTHOR]

Shell structures are among new and reliable structural systems in contemporary architecture with special characteristics such as gaining strength through form and interconnection with architecture form. They have attracted researchers once more in the present era from different aspects including stability, the new generation of shells and modern construction techniques. Therefore, because of their complicated behavior, the problem of finding and the process of determining their form have been obviously and specifically propounded and some solutions have been presented and applied to achieve the proper and optimal form. One of important these methods is the inverted hanging model. This method has been physically applied in finding compressive structures form for a long time since 17th century which was used firstly in arches, vaults and domes; and led to a variety and complex designs and It has become one of the methods to determine proper and various forms for shell due to its appropriation to the sell. The physical hanging model has been used in construction of various and many buildings some of which has been standing after too many years. Afterward the model has been formed and continued numerically because of its benefits, specifically due to its natural. Hence, it necessary to consider and recognize these methods for application, specifically those belong to the recent decades and form most of these approaches, in order to finding form and the related optimum form characteristics and suggesting better computational methods. Therefore, the purposes of the study are to find out the way of computational methods formation, based on the physical hanging model and the process of findings form in the methods; achieving optimal computational form's characteristics; access to numerical methods' features and determine the more proper solutions. In this regard we used descriptive- analysis and historical research methods to recognize the way of formation of all computational methods, based on the physical model methods, aiming at answering the goals of finding structural form as well as finding more proper ways to be applied currently. Hence, the shell structures' characteristics which should be considered in designing are extracted and determined from their definitions. Then, the issue of "finding the structural form" is assessed, because its definition and application is in sell structures, and different methods of finding their forms and their being targeted determine the methods are related to the reverse hanging model. Thereafter, the problem of "physical hanging model in finding the shell forms" is considered to recognize the hanging model theory, applied materials, purpose of hanging model, process and effective factors in achieving the form as well as the method and way of such model making. The main point is the computational hanging model methods in finding the shells' form that concentrates on the attempts to respond the research questions in the recent decade. Finally, we should conclude based on the reviews and analyses. Data collection instruments were library and internet sources. According to the findings of the study, the process of finding the form in computational method based on the physical methods is as following: The need for each step in physical form process is assessed during the numerical form process and their equivalents are considered through computed methods. In these methods, at the beginning of the process, also some assumptions and variables are determined in theory language, quantitatively and more precisely. The way of simulating external load, materials and bordering conditions are also revealed in the methods. The way of simulating the hanging model is also using theoretical methods and the way of converting cable into the arch remains unchanged, but it obviously differs from the physical method. The achieved form is the optimum primary form of the shell. To fix the form, some cases are tested based on a few methods including: "comparison with the shells made by famous people, in reality and in real scale"; "determining the allowed limits of the main parameters in the method and their relations based on the limits"; "determination of the allowed limits of important variables and their situation as well as other involving variables and then comparison with the results of the physical structure of the method" in two areas of "theory or theory and practice" and "real and practical". In this way, the process of form finding is done. The characteristics of the resulted optimal shape using the numerical methods are such as having the maximum rigidity or minimum bending, membrane behavior, the minimum energy, complexity and diversity shapes, and etc. Although computational methods are more accurate but the most characters of optimal computational form are the same as physical method and some characters such as minimal total energy and optimistic displacement are added. Forms may also have such characteristics and the methods acquire new characteristics of the forms could be existed. Most of the results achieved using various methods are the same. All methods are reliable for application except methods no. 3 and 1 and half of method no. 5. [ABSTRACT FROM AUTHOR]

The article discusses a deformation study on metallic capped end frusta with different geometrical section. Topics covered include the use of finite element analysis (FEA) to simulate the crush phenomenon, the effect of parameters such as weight, material and thickness on large deformation behavior and the role of friction on crush phenomenon.

Highlights: [•] An effective new 3-node shell element is derived from the MITC3 shell element. [•] The MITC3 shell element is enriched by a cubic bubble function for the rotations. [•] A new assumed transverse shear strain field is developed for the new element. [•] The numerical results demonstrate the excellent predictive capability. [Copyright &y& Elsevier]

Corrugated shell structures are widely used in civil, naval, automotive, and aerospace engineering because of their superior properties. In this paper, the nonlinear dynamic deformation of a class of longitudinally corrugated shell with a second-order differentiable wave under a uniform load was investigated. On the basis of their previous research result-that the corrugated shell undergoes large deformation but small strains-the authors proposed an assumption that the dynamic configuration of the corrugated shell is the same as the static configuration with a different load. Then the governing equations of the dynamic deformation of the corrugated shell were derived using Lagrange's equation, and an efficient numerical method without element discretization to solve those nonlinear differential equations was formulated. The accuracy of the present simplification was proved by comparing it with results obtained from a widely used nonlinear finite-element program, and the assumption on the dynamic configuration was shown to be applicable for most engineering applications. Furthermore, the developed method was adopted to perform parametric studies and it is found that the loading rates, the depth of wave, and the number of wave can greatly change the expansion velocity of the corrugated ring. And most importantly, the authors revealed that different corrugation types with the same ratio of the radius of the median surface to the depth of wave , the number of waves , and the circumference can yield similar dynamic expansion responses, which should be useful for future design of corrugated shell. [ABSTRACT FROM AUTHOR]

Highlights: [•] We propose a scheme to enrich the MITC3 shell finite element by interpolation covers. [•] The scheme increases the solution accuracy without any mesh refinement. [•] The enriched MITC3 shell element shows good convergence behavior. [•] The various numerical results demonstrate the feasibility and effectiveness. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, a nonlinear dynamic modeling method for a rigid–flexible coupling satellite antenna system composed of laminated shell reflector is proposed undergoing a large overall motion. For the study of the characteristics of the reflector using laminated shell structure, the displacement field description of a point in a 3-noded shell element is acquired in conjunction with the length stretch, lateral bending and torsional deformation. Hence, a nonlinear dynamic model of the satellite antenna system is deduced based on Lagrange's equations. The complete expressions of nonlinear terms of elastic deformation and coupling terms between rigid motion and large deflection are considered in the dynamic equations, and the dynamic behavior of the rigid–flexible coupling system is analyzed using linear model and nonlinear model, respectively. In order to eliminate the system vibration, the PD with vibration force feedback control strategy is used to achieve its desired angles and velocity in a much shorter duration, and can further accomplish reduction of residual vibration. Then, the asymptotic stability of the system is proved based on the Lyapunov method. Through numerical computation, the results show that the linear model cannot capture the motion-induced coupling terms and geometric nonlinearity variations. However, the nonlinear model is suitable for dealing with large deformation rigid–flexible problem undergoing large overall motions. Hence, the satellite antenna pointing accuracy would be predicted based on the nonlinear model. Furthermore, the results also show that the proposed control strategy can suppress system vibration quickly. The above conclusions would have important academic significance and engineering value. [Copyright &y& Elsevier]

Shell structures belong to a characteristic group of objects for which it is essential to know the magnitude and distribution of local deformations of the coat. Deformations may be important both in terms of stability, as well as special functions performed by these objects. While survey instruments usually ensure the required accuracy of the measurements, the methods for providing a mathematical description of the shape of shells do not always allow for a correct detection of deformations. This paper compares several methods of approximation potentially useful for making a precise description of the shape of a given shell object. Spline functions, as the most versatile tool in terms of description of objects shape, were adopted as the base method. For comparison purposes, according to the shape of the object in question, kriging and Fourier series methods were selected. Particular attention has been paid to the accuracy aspect, which has enabled deformations to be determined within centimeter or subcentimeter accuracy. Results of the study revealed the greatest overall accuracy of spline functions. This accuracy however decreases quickly when the observations become more irregular. Both, the past and future studies of the authors focus on integrating the best features of the described methods in order to ensure a high accuracy of the created models. The results may be useful not only in surveying but also in other fields associated with the approximation of surfaces based on measurement data. [ABSTRACT FROM AUTHOR]

Highlights: [•] The paper explains a new concept of solar electricity generation. [•] Therein extremely large engineering structures play a central role. [•] We elucidate the wind loading of solar chimneys with heights beyond code-validity. [•] We explain solar chimney responses: Hughe ring-stiffened thin shell structures. [•] Durability aspects of such shells of 120years of service-lives are discussed. [Copyright &y& Elsevier]

'Leicht Bauen mit Beton' und 'form follows force' sind die Motivation dieses Artikels. Es wird ein Prozess vorgestellt, wie das Entwerfen, Berechnen und Bemessen von sehr leichten und filigranen Freiformschalen aus Betonfertigbauteilen in der Zukunft aussehen könnte. Dafür werden neueste Methoden aus dem Bereich CAD-basierte Verfahren verwendet, welche eine sehr elegante Vereinigung von Design und Analyse ermöglichen. Der vorgestellte Prozess zeigt den Weg von der Entwurfsidee bis zur Bestimmung der optimalen Geometrie und Anordnung der Betonfertigbauteile. Design and Analysis of Curved Precast Concrete Components Using CAD-based Approaches - to build lightweight structures in the future 'Leicht Bauen mit Beton' and 'form follows force' are the motivation for this article. In this contribution a process is presented, which shows how the design and analysis of very light, free-form shells, made of precast concrete components, could be done in the future. Therefore, new techniques from the area of CAD-based methods are used, which allow for a very elegant way of integrating design and analysis. The presented process shows the path from the idea of the design to the determination of the optimal geometry and assembly of the precast concrete components. [ABSTRACT FROM AUTHOR]

Random charging processes effects on ground-state configurations and phase transition of a finite system have been investigated in terms of Hamiltonian system. The particles interact through a screened Yukawa potential and are confined by a two-dimensional parabolic potential. Numerical simulation was performed at low temperature for charging processes by particles collection and by photoemission. Results show that the charge fluctuation changes significantly the ground-state configurations only in the case of the photoemission charging process and give rise to a change on the melting characteristics. (© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [ABSTRACT FROM AUTHOR]

In this research, Method of Moving Asymptotes (MMA) is utilized for simultaneous shape and topology optimization of shell structures. It is shown that this approach is well matched with the large number of topology and shape design variables. The currently practiced technology for optimization is to find the topology first and then to refine the shape of structure. In this paper, the design parameters of shape and topology are optimized simultaneously in one go. In order to model and control the shape of free form shells, the NURBS (Non Uniform Rational B-Spline) technology is used. The optimization problem is considered as the minimization of mean compliance with the total material volume as active constraint and taking the shape and topology parameters as design variables. The material model employed for topology optimization is assumed to be the Solid Isotropic Material with Penalization (SIMP). Since the MMA optimization method requires derivatives of the objective function and the volume constraint with respect to the design variables, a sensitivity analysis is performed. Also, for alleviation of the instabilities such as mesh dependency and checkerboarding the convolution noise cleaning technique is employed. Finally, few examples taken from literature are presented to demonstrate the performance of the method and to study the effect of the proposed concurrent approach on the optimal design in comparison to the sequential topology and shape optimization methods. [ABSTRACT FROM AUTHOR]

Abstract: The objective of this study is to improve the performance of the MITC3 shell finite element. The Hellinger–Reissner (HR) variational principle is modified in the framework of the MITC method, and a special approximated transverse shear strain field is proposed. The MITC3-HR shell finite element improved by using the Hellinger–Reissner functional passes all the basic tests (zero energy mode test, patch test, and isotropic element test). Convergence studies considering a fully clamped plate problem, a sixty-degree skew plate problem, cylindrical shell problems, and hyperboloid shell problems demonstrate the improved predictive capability of the new 3-node shell finite element. [Copyright &y& Elsevier]

Abstract: Shells of variable radius of curvature may develop bending stress-resultants through the thickness under internal pressure. The severity of which depends on the rate of change of curvature of the mid-plane and the state of the boundary conditions . In particular elliptical cylinders will develop relatively large bending stresses and curvatures under internal pressure. A bend-free shell is a specially designed structure, in which the external loading results in a zero bending stress resultant and a zero change in curvature. This work investigates the possibility of creating such states in composite shells by steering the fibre-tows, and hence tailoring the local orthotropy. In particular, the simple ellipsoid of revolution is studied, and solutions found in terms of the spatial trajectories of the lamination parameters . Elliptical cylinders are also studied and the possibility of reducing bending deformation by tailoring extension-bend coupling explored. In general it was found that if the membrane hypothesis can be applied, then a totally bend-free shell may be designed by appealing to the materials constitutive equation. Doubly curved surfaces were found to be more amenable to the technique, while the moments in cylindrical shells were found to be impossible to suppress in the absence of additional secondary loading. [Copyright &y& Elsevier]

In the parameter free approach, FE-based data are used as design variables, such as nodal coordinates and nodal thickness. During shape and thickness optimisation, this approach provides much design freedom for a limited modelling effort. Stress results are, however, very sensitive to the local shape changes that can occur during parameter free optimisation. When stress results are used as response function, this irregularity can complicate the optimisation. As a solution, the Kreisselmeier-Steinhauser function for the stresses is introduced as a response function for parameter free shape optimisation. In this function, the local stress results are aggregated to obtain a global measure of stress in a structure. This measure can be used as an objective to reduce the overall stress in the structure or as a constraint to limit the stress in the structure to a maximum allowable value. As a result, the optimal structures are smooth and material efficient. Several examples are presented in this paper to illustrate the use of the parameter free design approach in combination with the stress response function. [ABSTRACT FROM AUTHOR]

Purpose |!|#8211; Laying the acoustic decoupling material on the surface of underwater structures is an effective noise reduction technology. The underwater sound radiation experiment of finite stiffened double cylindrical shell with separate-sound and decoupled tile is carried out with the aim of finding out the most effective laying condition. Design/methodology/approach |!|#8211; The segmentation power function interpolation method and vertex extreme value envelope continuation method are introduced into basic theory of empirical mode decomposition (EMD). The original measured sound pressure signals are decomposed to intrinsic mode function (IMF) group through EMD, and the high-frequency components are filtered out. Because the mechanical noise of submarine is mainly at low frequency, the IMFs in low frequency are researched through power spectrum analysis. The noise reduction effects of different separate-sound and decoupled tile laying conditions are compared. Findings |!|#8211; The sound pressure signal components|!|#39; amplitudes, periods and phases are obtained through EMD. The test data show that the double cylindrical shell entirely covered with separate-sound and decoupled tile is the most effective laying condition in noise reduction. Originality/value |!|#8211; With reference to the case study, this is believed to be the first application of the EMD in sound radiation time-frequency characteristics of double cylindrical shell. The evaluation of separate-sound and decoupled tile laying conditions is of great importance in engineering applications. [ABSTRACT FROM AUTHOR]

Abstract: As one component of our computational study of zinc-seamed pyrogallol[4]arene nanocapsules, we are investigating small mononuclear and polynuclear zinc complexes. In this article the results of our quantum chemical calculations on Zn(OH)2X2Y and Zn(OH)2X1,2Y2 complexes, where X is water or methanol and Y is pyridine or ammonia, are described. Structures and energetics obtained with the LanL2DZ vs. 6-311+G(d,p) vs. B2(pp) basis sets and DFT vs. MP2 methods are compared and contrasted. The effect of the hydroxide ligands on the preferred zinc coordination number and mode, inner- and outer-shell ligands, and hydrogen-bonding motifs is also examined. Trends in ligand binding energies are discussed. Of particular note is that the B3LYP/LanL2DZ calculations overemphasize the strength of both the conventional and unconventional hydrogen bonds. [ABSTRACT FROM AUTHOR]

Purpose – The purpose of this paper is to present integrated methodologies based on multilevel modelling concepts for finite element analysis (FEA) of reinforced concrete (RC) shell structures, with specific reference to account for the nonlinear behaviour of cracked concrete and the other associated features. Design/methodology/approach – Geometric representation of the shell is enabled through multiple concrete layers. Composite characteristic of concrete is accounted by assigning different material properties to the layers. Steel reinforcement is smeared into selected concrete layers according to its position in the RC shell. The integrated model concurrently accounts for nonlinear effects due to tensile cracking, bond slip and nonlinear stress-strain relation of concrete in compression. Smeared crack model having crack rotation capability is used to include the influence of tensile cracking of concrete. Propagation and change in direction of crack along thickness of shell with increase in load and deformation are traced using the layered geometry model. Relative movement between reinforcing steel and adjacent concrete is modelled using a compatible bond-slip model validated earlier by the authors. Nonlinear iterative solution technique with imposed displacement in incremental form is adopted so that structures with local instabilities or strain softening can also be analysed. Findings – Proposed methodologies are validated by evaluating ultimate strength of two RC shell structures. Nonlinear response of McNeice slab is found to compare well with that of experiment available in literature. Then, a RC cooling tower is analysed for factored wind loads to study its behaviour near ultimate load. Numerical validation demonstrates efficacy and usefullness of the proposed methodologies for nonlinear FEA of RC shell structures. Originality/value – The present paper integrates critical methodologies used for behaviour modelling of concrete and reinforcement with the physical interaction among them. The study is unique by considering interaction of tensile cracking and bond-slip which are the main contributors to nonlinearity in the nonlinear response of RC shell structures. Further, industrial application of the proposed modelling strategy is demonstrated by analysing a RC cooling tower shell for its nonlinear response. It is observed that the proposed methodologies in the integrated manner are unique and provide stability in nonlinear analysis of RC shell structures. [ABSTRACT FROM AUTHOR]

Abstract: In recent decades, the resistance of a structure has been thought of as well defined by the outcome of a geometrically and materially nonlinear analysis with explicitly modelled imperfections (GMNIA). But when this is the only analysis that is performed on a complex structural system, it is sometimes difficult to interpret the result. The outcome must be seen in the context of those from simpler analyses, which can define appropriate reference quantities. Other analyses, like a small displacement theory materially nonlinear analysis (MNA) and a linear elastic bifurcation analysis (LBA) are very important in the interpretation of a GMNIA. The general capacity curve in the Eurocode for shell structures provides a representation of these different analyses. Using this capacity curve, different identifiable key aspects of the structure''s behaviour can be studied independently and understood in relation to the corresponding parameter of this curve. This unified representation allows an easy and meaningful characterisation of all elastic–plastic buckling problems. However, some care is needed when applying such a generalised curve to structures with particular features. This paper outlines the limitations of the simplest version of the curve, and develops an enhancement that permits it to be deployed without restriction. [Copyright &y& Elsevier]

During the past few decades, a number of conical tanks have collapsed in various locations around the globe. Previous studies attributed the reason of collapse to inadequate thickness of the conical vessel especially at the bottom part. Most of the previous studies focused on studying the stability of conical tanks under the effect of only hydrostatic pressure. The current study focuses on studying the combined effect of wind loading and hydrostatic pressure on the stability of conical tanks. The study is conducted numerically, using a three-dimensional finite element model that is developed in-house. The critical imperfection shapes leading to minimum buckling capacity of conical shells under wind load alone, and under the combined effect of wind load and hydrostatic pressure, are determined. The study shows that a non-axisymmetric imperfection shape leads to minimum buckling capacity of empty conical tanks subjected to wind loads, while an axisymmetric distribution is noticed in the case of conical tanks under the combined effect of wind loads and hydrostatic pressure. In addition, the current study assesses the adequacy of an existing design procedure, which accounts for hydrostatic pressure, when the combination of hydrostatic pressure and wind load is considered. [ABSTRACT FROM AUTHOR]

Abstract: Steel conical vessels with upper cylindrical caps are widely used as liquid containments in elevated water tanks. This type of structure for containing water is referred to as “combined conical tank”. A number of catastrophic failures of combined conical tanks occurred during the past decades in various locations around the globe. Previous studies available in the literature focused on pure conical tanks, where the vessels have no upper cylindrical caps. The current study focuses on characterizing the buckling behaviour of combined conical tanks under the effect of hydrostatic pressure. The study is conducted numerically using a three-dimensional finite element model developed in-house. The effects of geometric imperfection and residual stresses as well as the variation of the geometric and material parameters on the buckling capacity of combined conical tanks are investigated. Finally, a comparison between the buckling capacities of combined and equivalent pure conical tanks is conducted. [Copyright &y& Elsevier]