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This publication presents a novel numerical avenue for the assessment of masonry structures. To circumvent the labor-intensive finite element method modeling and pre-processing step, the isogeometric analysis is enhanced within this contribution to cope with the necessities for masonry structures. This incorporates the study of apparent kinematic shell formulations, including their respective properties. Additionally, the connection towards non-linear material laws is outlined, and an empirically evaluated approach for the element size regularization is proposed. This generic approach would be inherently valid for other size dependent constitutive material models, as e.g. concrete models. The current paper is explored in the context of a number of experimental problems. These validation examples are used to provide structural assessments that extend beyond the scope of the experiment. Finally, a potential example that provides an outlook towards anticipated applications is presented. • Advancing the isogeometric analysis to cope with shell-based masonry structures. • Proposing a damage model in the context of the isogeometric analysis. • Newly proposed element length regularization technique for NURBS. • Enhancement of parametric and CAD-integrated workflow for masonry analysis. • Comprehensive mechanical assessments of masonry structures. [ABSTRACT FROM AUTHOR]

The present contribution presents the application of the newly developed isogeometric B-Rep analysis to the form-finding and structural analysis of structural membranes. Therefore, the necessary basis of the model description is briefly outlined. The result of this approach is the possibility to perform mechanically accurate form-finding (and follow-up analyses) directly within a CAD-environment on a full NURBS-based CAD-model. Selected benchmark examples show the accuracy and robustness of the developed method, assessed against analytical solutions if applicable. Two selected application examples that are entirely treated within the augmented CAD-environment highlight the potential of the method: Using one common model not only facilitates geometrical analysis and preparation of the model, but also allows for smooth and close interaction between design and analysis, which is of crucial importance in membrane design. [ABSTRACT FROM AUTHOR]

This contribution presents a computational engineering tool for the purposeful and systematic investigation how sensitive responses of a structural analysis model react due to variations of model parameters. The methodical basis of the approach is the relationship between adjoint sensitivity analysis and the classical and well-known technique of influence functions. The strong connection between the two approaches allows the extension of the traditional method of influence functions as a tool for the evaluation of sensitivities for general responses, parameters and structures. The paper provides a detailed discussion of that methodical relationship and shows how the influence function of important responses in structural engineering can be identified in the adjoint sensitivity equation. Following the ability of the traditional method of influence functions to provide structural comprehension as visual means, also the results of sensitivity analysis are graphically processed as maps. Finally, the application of the presented method and the sensitivity maps is demonstrated by means of expressive engineering structures. The examples provide insights how sensitivity analysis can support the structural design process by fast and purposeful identification and further assessment of the importance of model parameters. • The strong relation between influence functions and sensitivity analysis is shown. • The method of influence functions is generalized for sensitivity analysis. • Interpretation of sensitivity terms for practically important responses is given. • Sensitivity analysis is elaborated as engineering tool to enrich structural design. • Discussion concerning the significance and interpretation of sensitivities. [ABSTRACT FROM AUTHOR]

Abstract: Free form shells optimized for stiffness under given loading and membrane structures act in a pure membrane state of stresses, either because bending is minimized or not even present by definition. Physical experiments as soap films and hanging models have been used since centuries to generate optimal shapes of membranes in tension and shells in compression. The paper presents numerical methods to simulate the physical experiments as well as how they can be merged among each other and with the most general technology of structural optimization. The combined approach represents the combined power of each technique. Several examples illustrate the methods and typical applications. [Copyright &y& Elsevier]

• Finite element-based damage localization with coda wave interferometry. • Application of different solving algorithms that improve the damage localization. • Validation of the finite element-based approach with synthetic data. • Application of damage localization with coda wave interferometry at a real experiment. • Localization and distinguishing of multiple cracks in a real experiment. Coda wave interferometry is a structural health monitoring technique that allows the detection of cracks in concrete using diffuse ultrasound. This study develops a finite element-based methodology that computes a substitute model referred to as a sensitivity kernel. This kernel simulates the decorrelation development of two compared ultrasonic signals over the signals' length and allows to locate damage by solving an inverse problem. Results are compared to an established analytical approach. Two different solving techniques namely the LSMR method and one that respects upper and lower bounds on the variables called STIR are successfully applied in this study. The finite element-based methodology is validated with a reference simulation. In addition to the synthetic wave signals, the approach is tested on a real four-point bending test of a reinforced concrete specimen, where multiple cracks were successfully detected. [ABSTRACT FROM AUTHOR]

This publication presents a study aiming a macro characterization of the mechanical properties, suitable for future macro-scale numerical continuum-based analyses of a structured masonry bond, employing modern hollow bricks. The experiments themselves were initially simulated across different configurations, sizes and loading scenarios to determine the minimal specimen size invariant to boundary and size effects that scales consistently. From these simulations, a numerically informed experimental program was executed across compression, tension, shear, triplet shear, and out-of-plane bending conditions to fully quantify orthotropic material parameters of the masonry pattern suitable for aimed macro-scale simulation. The outcome of this publication is a comprehensive quantitative understanding of the apparent masonry type for engineering design purposes. • Structured masonry bonds with modern hollow bricks. • Numerical masonry classification. • Orthotropic macroscopic plane-stress. • Macro scale experimental tests. [ABSTRACT FROM AUTHOR]

In this study, we evaluate lattice Boltzmann and finite element methods for wind load estimation of parabolic trough solar collectors. Mean, root-mean-square (RMS) and peak values of aerodynamic load coefficients of an isolated collector are estimated using large-eddy simulation and compared with experimental results obtained in a boundary layer wind tunnel. Despite their fundamental differences, the two numerical approaches yield similar values for the drag, lift and pitching moment indicating that the results are essentially independent of the numerical schemes. Time-varying inlet boundary conditions are obtained using an efficient synthetic generation technique. The statistics of the numerical boundary layer are investigated by comparing mean and turbulence intensity profiles at varying distances from the inlet as well as the spectra and autocorrelation at the position of the structure. Through appropriate modelling of the boundary layer, the numerical models are shown to reproduce the mean, RMS and peak load behaviour measured in the wind tunnel. [ABSTRACT FROM AUTHOR]

Co-simulation is a popular numerical method to solve complex multiphysics problems. The co-simulation method has an intrinsic advantage: it allows well-established and specialized simulation tools to be reused and combined with minor adaptations, in contrast to the monolithic approach. We employ a novel co-simulation approach to simulate a fully-coupled emergency brake maneuver scenario of the National Renewable Energy Laboratory (NREL) Unsteady Aerodynamics Experiment (UAE) Phase VI wind turbine. Within this simulation the acceleration and deceleration of the turbine are a result of the interaction of the blades, generator/gearbox, control unit and the flow field. The simulation results are validated against measurement data from the NREL UAE Phase VI performed in the NASA AMES wind tunnel. Using the co-simulation approach, in contrast to the investigations of various other research groups, this work provides a methodological framework to perform simulations much closer to real physics. This is realized by taking into account the interaction of blades, generator/gearbox, control unit and fluid at the same time. Thus, the usual approximations and assumptions on the single fields, which become necessary due to the artificial decoupling, are not needed, e.g. prescribing certain behavior. Moreover, the full flexibility of co-simulation is combined with the stability of a monolithic approach applying the novel Interface Jacobian-based Co-Simulation Algorithm (IJCSA). [ABSTRACT FROM AUTHOR]

This paper is concerned with the analysis of the pure torsion and distortion of straight box beams with trapezial cross-sections and hinged walls. A one-dimensional mechanical model for this kind of system subjected to anti-symmetric loads on the end cross-sections and no warping constraints is developed. The distortional stiffness of the system is provided by the torsional rigidity of the wall panels. The cross-sectional kinematic condition for which torsion and distortion are uncoupled has been determined. Novel explicit expressions of the internal and external distortional moments, the distortion constant, and the distortional warping pattern have been deduced; they can be directly translated to the classical distortion theory. Results of representative test cases with different section shapes and loads show excellent agreement with finite element models using shell elements. The model is a first step to analyse bridge decks with a distortionable central cell for wind engineering applications. Finally, an extension of the model, including the distortional stiffness provided by the frame bending stiffness of the cross-section walls, is presented. The extended model is applicable to assess the large-scale torsional–distortional effects in long beams with closed cross sections. [Display omitted] • 1D model for pure torsion and distortion of trapezial box beams with hinged walls. • The kinematic reference for uncoupling torsion and distortion has been determined. • Explicit formulas for distortional moment, distortion constant and warping pattern. [ABSTRACT FROM AUTHOR]

Recent advances of the numerical wind tunnel result in a flexible methodological framework, which enables the fully-coupled simulation of wind-structure interactions considering the arbitrary and modular inclusion of additional devices into the system – such as added mass dampers – for the mitigation of vibrations caused by the wind flow. This feature could be seen as an add-on to what can be done with experimental methods and enables further possibilities when the predictive character of such simulations is used for structural design or even for the development and optimization of the additional devices themselves. The procedure promotes an approach fully-solved in time domain using a multiply-partitioned concept to be able to deal with the respective components in an efficient way. It is crucial to adopt a coupled approach and analysis in time as the involved systems can heavily influence each other. The systematic preparation of each module accompanied by coupled simulations is presented, which aims to ensure and enhance the quality of the overall solution strategy. The effectiveness and industrial relevance of the concept is presented on a tall building undergoing dynamic excitation due to vortex shedding with an integrated vibration mitigation device. [ABSTRACT FROM AUTHOR]

We investigate the wind-excited torsional vibration of a parabolic trough solar collector using large eddy simulation. Past studies of wind loads on parabolic trough solar collectors have used rigid models, thereby neglecting possible feedback effects of structural motion on wind loads. Therefore, the primary aim of this study is to assess the extent to which feedback effects of the structural motion on aerodynamic loading can affect the response. To this end, we perform both one-way and two-way coupled fluid-structure interaction simulations corresponding to rigid and aeroelastic models, respectively. In both cases, the collector is exposed to realistic time-varying wind gusts in order to account for their effect on the flow instabilities around the structure. Comprehensive data obtained by numerical simulation is analyzed to provide new insight into the transient flow behavior around a collector and its interaction with the torsional vibration. We show that significant self-excited vibrations can occur for certain pitch angles. The onset of self-excited vibrations coincides with the synchronization of the vortex shedding process with the torsional vibration of the collector. [ABSTRACT FROM AUTHOR]

• Application of partitioned dynamic structural finite element analysis. • Stability and accuracy evaluation of non-conforming FEM-FEM coupling technologies. • Comparison of Gauss–Seidel and FETI-based FEM-FEM coupling approaches. • Effect of origin/destination designation on FETI-based coupling. • Partitioned coupling approaches computationally competitive with monolithic solution. Contrasting monolithically solved numerical analyses, partitioned coupled simulations confer the substantial advantages of software modularity, employing the best numerical techniques for each domain and readiness to extend the coupling to other physics and emerging numerical techniques. However, an additional interface problem is created and must be solved without significantly deteriorating solution accuracy. This application-oriented study examines non-conforming partitioned dynamic FEM-FEM simulations under approaches of varying complexity illustrating their ranges of applicability as well as key advantages and disadvantages. After presenting the pertinent aspects of popular coupling technologies, two numerical examples of different complexities are considered. Although the efficiently simple Gauss–Seidel approach is suitable for partitioned systems of dissimilar stiffnesses, such as structure and fluid/soil interaction, stability and accuracy deteriorate as domain compliances align rendering it unsuitable for partitioned structural analysis. Contrasting this, the more robust FETI-based method maintains stability over all stiffness ratios and demonstrates excellent agreement with equivalent monolithic structural responses in terms of displacements and stresses. [ABSTRACT FROM AUTHOR]