Design of an Analysis Environment for Planning Decision Support

In this contribution, the design of an analysis environment is presented, that supports an analyst to come to a decision within a gradual collaborative planning process. An analyst represents a project manager, planner or any other person, involved in the planning process. Today, planning processes are managed by several geographically distributed planners and project managers. Thus, complexity of such a process rises even more. Prediction of consequences of many planning decisions is not possible, in particular since assessment of a planning advance is not trivial. There have to be considered several viewpoints, that depend on individual perceptions. In the following, methods are presented to realize planning decision support

Variation of Reference Strategy - A Novel Approach for Generating Optimized Cutting Patterns of Membrane Structures

AbstractFinding the plane shape of the double curved surfaces is a well-known challenge for every design engineer dealing with either fiber reinforced plastics lightweight designs or textile architectural membranes. A novel approach for generating optimized cutting patterns including nonlinear isotropic and anisotropic material behavior is presented. The so-called Variation of Reference Strategy can be seen as an inverse approach, defining the nodal positions in the material configuration as design variables holding the spatial configuration fixed. Thereby, the stress-free state of the cutting pattern which is an important characteristic of the manufacturing process is preserved. In order to demonstrate the abilities and robustness of the Variation of Reference Strategy several numerical examples considering different kind of materials are presented

A modified particle swarm optimizer and its application to spatial truss topological optimization

p. 1044-1057Particle Swarm Optimization (PSO) is a new paradigm of Swarm Intelligence which is inspired by concepts from 'Social Psychology' and 'Artificial Life'. Essentially, PSO proposes that the co-operation of individuals promotes the evolution of the swarm. In terms of optimization, the hope would be to enhance the swarm's ability to search on a global scale so as to determine the global optimum in a fitness landscape. It has been empirically shown to perform well with regard to many different kinds of optimization problems. PSO is particularly a preferable candidate to solve highly nonlinear, non-convex and even discontinuous problems. In this paper, one enhanced version of PSO: Modified Lbest based PSO (LPSO) is proposed and applied to one of the most challenging fields of optimization -- truss topological optimization. Through a benchmark test and a spatial structural example, LPSO exhibited competitive performance due to improved global searching ability.Yang, B.; Bletzinger, K. (2009). A modified particle swarm optimizer and its application to spatial truss topological optimization. Editorial Universitat Politècnica de València. http://hdl.handle.net/10251/676

Computational morphogenesis of free form shells: Filter methods to create alternative solutions

p. 536-547Actual trends in numerical shape optimal design of structures deal with handling of very large dimensions of design space. The goal is to allowing as much design freedom as possible while considerably reducing the modelling effort. As a consequence, several technical problems have to be solved to get procedures which are robust, easy to use and which can handle many design parameters efficiently. The paper briefly discusses several of the most important aspects in this context and presents many illustrative examples which show typical applications for the design of light weight shell and membrane structures.Bletzinger, K.; Firi, M.; Linhard, J.; Wüchner, R. (2009). Computational morphogenesis of free form shells: Filter methods to create alternative solutions. Editorial Universitat Politècnica de València. http://hdl.handle.net/10251/654

Conception and design of membrane structures considering their non-linear behavior

The lack of unified verification approaches and standards like the Eurocodes for various materials is a limiting factor to further propagation of architectural membranes. This paper will discuss the possibilities and challenges of integrating the design and verification of membrane structures into the Eurocodes’ philosophy. Therefore an overview of existing guidelines will be given, followed by a discussion of the underlying principles of the Eurocodes. Especially the non-linear behavior of architectural membranes distinguishes them from other structures. Therefore the focus of this contribution is to discuss the implications of this non-linearity on verification approaches. Theoretical considerations as well as in-depth examples help to clarify the necessary basis. Finally the consequences of non-linearity on the verification of the primary structure and hybrid structures are presented

Advanced cutting pattern generation – Consideration of structural requirements in the optimization process

This paper presents extensions to optimized cutting pattern generation through inverse engineering regarding structural requirements. The optimized cutting pattern generation through inverse engineering is a general approach for the cutting pattern generation which is based on the description of the underlying mechanical problem. The three dimensional surface, which is defined through the form finding process, represents the final structure after manufacturing. For this surface the coordinates in three dimensional space Ω3D and the finally desired prestress state σprestress are known. The aim is to find a surface in a two dimensional space Ω2D which minimizes the difference between the elastic stresses σel,2D→3D arising through the manufacturing process and the final prestress σprestress. Thus the cutting pattern generation leads to an optimization problem, were the positions of the nodes in the two dimensional space Ω2D are the design variables. In this paper various improvements to the method will be shown. The influence of the seam lines to the stress distribution in the membrane is investigated. Additionally, the control of equal edge length for associated patterns is an example for important enhancement

The eXtended Updated Reference Strategy for the form finding of tensile structures

In this paper, the eXtended Updated Reference Strategy is presented. Starting from the established Updated Reference Strategy all related issues, which are involved for this methodology, are identified. It will be shown that the eXtended Updated Reference Strategy is able to solve the “correct” form finding problem in one non-linear iteration step. By applying the eXtended Updated Reference Strategy to well-known form finding problems the difference in convergence in comparison to establish methods like the force density method or the Updated Reference Strategy is discusse

Using nurbs as response surface for membrane material behavior

This work proposes a NURBS for the determination of a smooth response surface relating biaxial strains and stresses from discrete test data. These NURBS surfaces are based on two axes of strain and one axis of stress. The constitutive material tensor is calculated with the derivatives of the NURBS surfaces and curves. The motivation of the proposed work came from the use of new materials in membrane structures that requires complex material models to describe the complex material behavior. A method for the establishment of a matrix of material coefficients from these surfaces is developed aiming its application in finite element models. The response surface stress-strain relation and the material matrix derived are compared to classical hyperelastic and MooneyRivlin material models. The response surface approach using NURBS allows for an easy implementation in an existent FE code, requiring few changes. A similar application is found in the work of Bridgens and Gosling [1]. This approach provides a direct correlation between stresses and strains in the wide range of possible stress paths the material is subject to. Curve fitting based on least squares approximation is employed to generate NURBS surfaces for the experimental data. The advantage of this material model is that a smooth stress-strain response surface can be obtained directly from the experimental results. On the other hand, in order to generate good NURBS surfaces the experimental data should provide an adequate point distribution. This could require a large range of experimental data. We conclude that this material model is a good alternative to conventional material models for complex material behavior

Pressure-volume coupling in inflatable structures

Inflatable structures or pneumatic structures are air-supported structures and find application in a variety of new engineering projects. By these structures the gas gives shape and strength to the structure in such a way that with larger volumes and higher pressures larger spans can be abridged. Their architectonic flexibility and the search for better structural efficiency are strong favorable arguments to the use of this kind of structure. Furthermore, inflatable structures can be erected or dismantled quickly, are light, portable and materially inexpensive. Also, some characteristics such as the utilization of natural lighting and ventilation and its possibility of reuse contribute to the pursuit of sustainable development. In this work the influence of the pressure-volume coupling on structure behavior is studied. A membrane formulation with deformation-dependent forces was implemented in a finite element model to take into account the influence of gas volume variation, with corresponding change in pressure for enclosed gas on the stiffness of membrane structures. An analytical solution of inflatable membranes was developed for the validation of the numerical results. Comparisons are carried out on a clamped circular membrane inflated by a uniform pressure

Nichtlineare Optimierung geometrisch definierter Fugen von räumlich gekrümmten Betonfertigteilen mit isogeometrischen Verfahren

Die Vision dieses Projektes ist es, einen durchgängigen Prozess zu entwickeln, der es erlaubt, den Entwurf, die Berechnung und die Fugenoptimierung von flächigen Strukturen aus Betonfertigteilen sehr einfach und effizient durchzuführen. Damit soll die Herstellung von freien Formen, wie beispielsweise „Blobs“ und Hängeformen aus Beton, unterstützt und gefördert werden.The vision of this project is to develop a continuous process that allows very easy and efficient design, calculation and joint optimization of surface-like structures made of precast concrete elements. This should support and encourage the production of free forms, such as “blobs” and hanging forms made of concrete