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An adjoint-based procedure to determine weaknesses, or, more generally the material properties of structures is developed and tested. Given a series of force and deformation/strain measurements, the material properties are obtained by minimizing the weighted differences between the measured and computed values. Several examples with truss, plain strain and volume elements show the viability, accuracy and efficiency of the proposed methodology using both displacement and strain measurements. An important finding was that in order to obtain reliable, convergent results the gradient of the cost function has to be smoothed.

Die Weltbevölkerung wächst und gleichzeitig werden die Ressourcen immer knapper. Einen großen Anteil daran hat das Bauwesen. Die Lösung für ressourceneffizientes Bauen, sei es auf dem Wasser oder an Land, sehen Expertinnen und Experten in anpassungsfähigen, so genannten adaptiven Strukturen. Sie beschreiben die Idee, wie künftig für mehr Menschen ressourcenschonend und emissionsfrei gebaut werden kann. Dabei soll nicht nur mehr Wohnraum mit weniger Material geschaffen werden, sondern auch der Energieverbrauch gesenkt und der Nutzerkomfort gesteigert werden. Über den neuesten Stand der Technik diskutieren Expertinnen und Experten aus Wissenschaft und Wirtschaft am 23. und 24. Mai im Rahmen des Workshops „Adaptive Structures at Shore“ an der Technischen Universität Hamburg. In unterschiedlichen Fachvorträgen geht es einerseits darum, welche Auswirkungen beispielsweise Wind und Wasser auf Kaimauern oder schwimmende Bauwerke haben, oder inwiefern eine hohe Verkehrslast Brücken beansprucht. Dabei stellt sich die Frage, wie Bauwerke nachhaltig auf entsprechende Herausforderungen optimiert und angepasst werden können und inwiefern dabei Modellierungen und Simulationen helfen können. Der interdisziplinäre, englischsprachige Workshop wird durch das TU-Institut für Geotechnik und Baubetrieb organisiert und richtet sich an Interessierte unterschiedlicher Fachbereiche aus Wissenschaft, Wirtschaft und Verwaltung., Adaptive structures at shore provide an opportunity to minimize the resource consumption and the impact on the marine ecosystems through an efficient adaptation to changing boundary conditions. A combination of impact prediction, monitoring and material resistance estimation, numerical modelling, and innovative design is the key to success. The workshop “Adaptive Structures at Shore 2022” hosted by Hamburg University of Technology (TUHH) brings together international scientists and professionals to discuss the latest developments in the field and to explore synergies.

This paper proposes a new partitioned coupling approach to simulate the wind induced excitation of a membrane structure with ponding water. This approach uses three different solvers to simulate wind, water and membrane structure. The main assumption here is that the interaction between the wind and water can be neglected due to the small depth and small fetch of the water, relative to the size of the membrane structure. This assumption results in a coupling strategy where the structural solver independently interacts with the wind and water solver. The results from this method is compared with a straightforward approach, where a two-phase solver, modeling the wind and water, is coupled to a structural solver. The obtained results agreed very well with the reference modeling approach, where all the interactions are taken into account. Furthermore, the proposed method was found to be computationally more efficient.

Traditional computational methods face significant challenges with ever-increasing complexity in the problems of engineering interest. One category of problems that suffer from this phenomenon is those where Fluid-Structure Interaction (FSI) is present. One set of problems that suffer from this phenomenon is those where Fluid-Structure Interaction (FSI) is present. FSI simulations are traditionally time-consuming and computationally extremely expensive. Potential alternatives rely on using a surrogate model to substitute one or more systems involved. A promising approach employs artificial neural networks as the basis for such a surrogate model combined with strong physics simulations based on finite element methods (FEM). This approach requires the seamless integration of AI algorithms and packages into the simulation workflow. Such an example is the NeuralNetworkApplication developed in KratosMultiphysics. The routines related to the neural networks are executed through an interface with the Keras API. Mok's benchmark is chosen as the study case to test the capacity of the previous method applied to FSI problems. Two cases in which one of the systems is substituted by a neural network-based surrogate model are analyzed. Strong and weak coupling scenarios are considered. The results present improvements in simulation time without sacrificing accuracy, especially when compared with the original benchmark. This contribution discusses the influence of the original data and network architecture on the simulation outcome and different considerations for generating surrogate models for FSI.

The sensitivity of membrane structures to wind loads due to their flexibility and small inertial masses raises the question of their behavior under natural wind conditions. Particularly transient wind loads could lead to dynamic amplification of the structural response. The assessment of the dynamic response of membrane structures is complex due to their special load carrying behavior, their material properties, and their distinct structural interaction with flow induced effects. Computationally intensive fluid–structure interaction simulation could overcome simplifications and limitations of existing approaches, especially small scale wind tunnel tests, and allow the assessment of all relevant structural and fluid phenomena. This paper outlines a virtual design methodology for lightweight flexible membrane structures under the impact of fluctuating wind loads and provides results on the unique validation of the method at real-scale tests of a highly flexible 29m umbrella.

This article presents a staggered approach to couple the interaction of very flexible tension structures with large deformations, described with the finite element method (FEM), and objects undergoing large, complex, and arbitrary motions discretized with particle methods, in this case the discrete element method (DEM). The quantitative solution quality and convergence rate of this partitioned approach is highly time step dependent. Thus, the strong coupling approach is presented here, where the convergence is achieved in an iterative manner within each time step. This approach helps increase the time step size significantly, decreases the overall computational costs, and improves the numerical stability. Moreover, the proposed algorithm enables the application of two independent, standalone codes for simulating DEM and structural FEM as blackbox solvers. Systematic evaluations of the newly proposed iterative coupling scheme with respect to accuracy, robustness, and efficiency as well as cross comparisons between strong and weak FEM-DEM coupling approaches are performed. Additionally, the approach is validated against the rest position of an impacting object, and further examples with objects impacting highly flexible protection structures are presented. Here, the protection nets are described with nonlinear structural finite elements and the impacting objects as DEM elements. To allow the interested reader to independently reproduce the results, detailed code and algorithm descriptions are included in the appendix.

The maturity of numerical techniques both in Computational Structural and Fluid Dynamics, accompanied by the availability of affordable high-performance hardware, allows the use of virtual rapid-prototyping facilities as realistic alternatives to traditional wind tunnel experiments. This work aims to present a virtual wind tunnel tool that combines both “standard” body-fitted approaches and innovative embedded techniques. Two are the distinctive features of the work. Firstly, it allows the simulation of membrane structures subjected to large displacements. This is typically challenging both for embedded solvers, due to the need of modelling a strong discontinuity of the flow field in correspondence of the structural position, and for body-fitted techniques, due to the large displacement regime. Secondly, it allows combining body fitted and embedded structures within the same simulation. All the presented strategies are developed both in Open MP and MPI.

Hybrid, bending-active structures constitute a challenging task for structural design due to the high dependency between shape and forces. Isogeometric analysis suggests itself in this context because of several advantages. Model conversion with concomitant corruption of the simulation results can be overcome. All stages of the construction, which are necessary for the correct simulation of such structures, can be modeled and correctly linked. Moreover, the parameter space of the NURBS description provides a perfectly suited, additional design space for embedded entities, which can be defined independently of the parametrization. The contribution of this paper is a presentation of the basics for embedding within isogeometric analysis and reveals beneficial aspects of nested NURBS descriptions in the context of staged construction. A case study of a staged simulation is carried out and another one for the form-finding procedure of hybrid structures.

This paper studies the transition from downscaled wind tunnel testing to prototype scale numerical simulations. The study is performed using OpenFOAM as fluid solver, EMPIRE as coupling tool, and Carat++ as the structure solver. The current work aims at finding sufficient settings for wind-structure interaction simulations. Also, the efficiency of the software chain to simulate natural wind flow is approved. For this purpose, different flow conditions such as uniform, atmospheric boundary layer (ABL), and flow behind a cube (structure is positioned in the wake region behind a cube) are simulated. These complicated, unsteady, and recirculating flows are simulated to study the aeroelastic effects on light weight shell structures. Wind-structure interaction simulations are performed where the dynamics of the structure play a crucial role in the wind effects. An Aluminum shell structure was tested in the wind tunnel to have an experimental benchmark for aeroelasticity. Throughout spectral analysis of structure vibrations and statistical evaluation of forces, the modeling approach shows a very good agreement with the experimental results. Finally, scaling issues represent a great challenge to wind tunnel testing especially when it comes to light-weight structures. While significantly, numerical simulations are shown to be an efficient tool for the prediction of wind loading on structure under different wind conditions.

International audience; Designing large ultra-lightweight structures within a fluid flow, such as inflatable hangars in an atmospheric environment, requires an analysis of the naturally occurring fluid-structure interaction (FSI). To this end multidisciplinary simulation techniques may be used. The latter, though, have to be capable of dealing with complex shapes and large deformations as well as challenging phenomena like wrinkling or folding of the structure. To overcome such problems the method of embedded domains may be used. In this work we discuss a new solution procedure for FSI analyses based on the method of embedded domains. In doing so, we are in particular answering the questions: How to track the interface in the embedded approach, how does the subsequent solution procedure look like and how does both compare to the well-known Arbitrary-Lagrangian-Eulerian (ALE) approach? In this context a level set technique as well as different mapping and mesh-updating strategies are developed and evaluated. Furthermore the solution procedure of a completely embedded FSI analysis is established and tested using different small- and large-scale examples. All results are finally compared to results from an ALE approach. It is shown that the embedded approach offers a powerful and robust alternative in terms of the FSI analysis of ultra-lightweight structures with complex shapes and large deformations. With regard to the solution accuracy, however, clear restrictions are elaborated.

Actual 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.

This paper presents an effective method to perform Code Verification of a software which is designed for structural analysis using membranes. The focus lies on initially curved structures with large deformations in steady and unsteady regimes. The material is assumed to be linear elastic isotropic. Code Verification is a part of efforts to guarantee the code’s correctness and to obtain finally predictive capability of the code. The Method of Manufactured Solutions turned out to be an effective tool to perform Code Verification, especially for initially curved structures. Here arbitrary invented geometries and analytical solutions are chosen. The computer code must approach this solution asymptotically. The observed error reduction with systematic mesh refinement (i.e. observed order of accuracy) must be in the range of the formal order of accuracy, e.g. derived by a Taylor series expansion. If these two orders match in the asymptotic range, the implemented numerical algorithms are working as intended. The given examples provide a complete hierarchical benchmark suite for the reader to assess other codes, too. In the present case several membrane states were tested successfully and the used code Carat++ assessed to converge - as intended - second order accurately in space and time for all kind of shapes and solutions

This work proposes novel methods and strategies for enhancing the robustness, accuracy, and efficiency of multiphysics simulations with a particular focus on fluid-structure interaction (FSI) problems. At its core, the present work deals with two main aspects of the FSI problems: stable and accurate temporal discretization of FSI problems, including non-matching time steps, and enhanced robustness and efficiency of interface quasi-Newton convergence acceleration methods for the FSI simulations. In der vorliegenden Arbeit werden neue Methoden und Strategien zur Erhöhung der Robustheit, Genauigkeit und Effizienz von Multiphysik-Simulationen mit besonderem Schwerpunkt auf Fluid-Struktur-Interaktionsproblemen (FSI) vorgeschlagen. Im Kern befasst sich diese Arbeit mit zwei Aspekten von FSI-Problemen: stabile und genaue zeitliche Diskretisierung von FSI-Problemen, einschließlich nicht übereinstimmender Zeitschritte; und Robustheit und Effizienz von Quasi-Newton-Methoden für FSI-Simulationen.

Flexible rockfall nets are installed in the mountains, mainly at exposed locations such as infrastructure and settlements. Due to the pronounced interaction of load case and structural response, generally applicable load approaches are difficult to derive. This work presents a partitioned coupled simulation method for the numerical analysis of the interaction between the impacting object and the protective structure. Particle methods are combined with the finite element method. Flexible Steinschlagnetze werden in Gebirgen vor allem an exponierten Stellen wie Infrastruktur und Siedlungen installiert. Durch die ausgeprägte Wechselwirkung von Lastfall und Strukturantwort sind allgemeingültige Lastansätze nur schwer herleitbar. Zur numerischen Analyse der Interaktion von einschlagendem Objekt und der Schutzstruktur stellt diese Arbeit eine partitioniert gekoppelte Simulationsmethode vor. Dabei werden Partikelmethoden mit der Finiten Elemente Methode zusammengebracht.

Die Arbeit umfasst drei Teilaspekte des Structural Health Monitoring der Tragstruktur von Windenergieanlagen: den Entwurf eines optimierten Messaufbaus, die automatische Überwachung modaler Parameter und die Lebensdauerprognose basierend auf Ermüdungsschädigung. Für die Lebensdauerprognose wurde ein modellbasiertes Vorgehen genutzt, mit einer Modellvalidierung basierend auf modalen Parametern und gemessener Lasten, die am Beton-Stahl Hybridturm einer 3 MW Windenergieanlage erhoben wurden. This work covers three aspects of structural health monitoring of the support structure of wind turbines: the design of an optimized measurement setup, the automatic monitoring of modal parameters and the remaining useful life prediction based on fatigue damage. For lifetime prediction, a model-based approach was employed, with model validation based on modal parameters and measured loads that were obtained from a concrete-steel hybrid tower of a 3 MW wind turbine.

Domain decomposition(DD), both overlapping and non-overlapping type, are pivotal in enabling numerical simulation of several elaborate engineering models and complex multiphysics phenomena. A novel monolithic modification to master-slave elimination approach is introduced to solve Chimera problems in CFD, including MPI parallelization technique. In the context of partitioned simulations the current work proposes a novel detached-interface approach for realizing a generic co-simulation framework. Die Domänenzerlegung (DD), sowohl überlappend als auch nicht überlappend, ist von zentraler Bedeutung für die numerische Simulation komplexen multiphysikalischen Phänomenen. Eine neuartige monolithische Modifikation des Master-Slave-Eliminierungsansatzes wird eingeführt, um Chimera-Probleme in CFD zu lösen, einschließlich MPI-Parallelisierung. Im partitionierten Simulationen schlägt die aktuelle Arbeit einen neuartigen Detached-Interface Ansatz in eines generischen Co-Simulations-Frameworks vor.