Kai-Uwe Bletzinger

Technische Universität München | TUM · Institut für methodische Grundlagen im Bauwesen

Monitoring and assessing infrastructure health are prerequisites for efficient maintenance. New technologies and methods enable deeper insights and thus offer improved information for decision makers. The development of such new methods for application requires holistic understanding not only of the method itself, but also of the specific challenge...

The Vertex Morphing method is a node-based shape parameterization that uses an explicit filtering approach to regularize the optimization problem and generate smooth shapes. It has been successfully applied to shape optimization problems of industrial size in recent years. This work investigates in detail how irregular discretizations, design surfa...

In the industrial sector, products evolve significantly over their operational life. A key challenge has been maintaining precise, relevant engineering data. This paper explores the digital twin concept, merging engineering and operational data to enhance product information updates. It examines digital twin applications in construction, material f...

This paper presents the experimental results of a 1:1 scale prototype of a segmented pedestrian bridge produced by the Additive Manufacturing (AM) technology Selective Paste Intrusion (SPI). SPI employs a technique where aggregates are selectively bound layer-by-layer in a particle bed with cement paste, enabling the 3D printing of large-scale, fre...

One of the biggest challenges in optimizing the shape of complex solids is the requirement to maintain a reasonable mesh quality not only at the boundary but also for the bulk discretization of the interior. Thus, additional regularization and, in many cases, re-meshing of the structure during the iterative process is unavoidable with a Lagrangian...

Embedded and immersed methods have become essential tools in computational mechanics, as they allow discretizing arbitrarily complex geometries without the need for boundary-fitted meshes. One of their main challenges is the accurate numerical integration of cut elements. Among the various integration schemes developed for this purpose, moment fitt...

Modular precast construction is a methodological approach to reduce environmental impacts and increase productivity when building with concrete. Constructions are segmented into similar precast concrete elements, prefabricated with integrated quality control, and assembled just-in-sequence on site. Due to the automatised prefabrication, inaccuracie...

The Material Point Method (MPM) is an established and powerful numerical method particularly useful for simulating large-scale, rapid soil deformations. Therefore, it is often used for the numerical investigation of mass movement hazards such as landslides, debris flows, or avalanches. It combines the benefits of both mesh-free and mesh-based conti...

This research presents a constitutive model for the macro scale simulation of masonry structures. The model is containing an orthotropic plane stress assumption, which appears as an appropriate assumption for the in-plane analysis of masonry walls. The material model is based upon damage mechanics, split into tensile and compression parts. The nove...

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 s...

Topology optimization can produce optimal geometries in terms of the simulated physics, but they are primarily represented as watertight surface meshes which enclose a volume. As a result, they cannot be incorporated directly into the design process, which is mainly carried out using Computer Aided Design (CAD) data. To enable the integration into...

We introduce a novel hybrid methodology that combines classical finite element methods (FEM) with neural networks to create a well-performing and generalizable surrogate model for forward and inverse problems. The residual from finite element methods and custom loss functions from neural networks are merged to form the algorithm. The Finite Element...

This work studies shape filtering techniques, namely the convolution-based (explicit) and the PDE-based (implicit), and introduces the implicit bulk-surface filtering method to control the boundary smoothness and preserve the internal mesh quality simultaneously in the course of bulk (solid) shape optimization. To that end, the volumetric mesh is g...

We present a first-order method for solving constrained optimization problems. The method is derived from our previous work, a modified search direction method inspired by singular value decomposition. In this work, we simplify its computational framework to a ``gradient descent akin'' method (GDAM), i.e., the search direction is computed using a l...

In this work, a modular coupling approach for particle methods with the FEM (finite element method) is presented. The proposed coupled strategy takes advantage from the ability of particle methods of dealing with large displacements and deformations, especially when solving complex fluid–structure and solid–structure interaction problems. The coupl...

This publication presents a novel CAD‐integrated avenue for structural analyses of modular constructions, by applying the isogeometric analysis. The approach relies on trimming of segments from an original geometry and allows accordingly to introduce kinematics at the interfaces and to assess the connections of the parametrically defined modules. T...

The implementation of machine learning for the real-time prediction of the suitable value of the damping ratio of a semi-active tuned mass damper (SA-TMD) is investigated to ensure enhanced vibration control in vehicle-bridge interaction (VBI) problems. The response assessment of the uncontrolled, tuned mass damper (TMD)-controlled, and SA-TMD-cont...

Direct usage of construction plans as input for structural analyses assumes the reference configuration to match the engineering drawings. However, the built construction is typically supposed to match the construction plans after its successful erection. In that state, the structure is usually already subjected to self-weight and maybe other loadi...

This publication presents required steps for the realization of the pre- and post-processing for the isogeometric analysis and the isogeometric B-Rep analysis, with a focus on the collection of required data. It reveals the essential prerequisites for the preparation and the collection of geometrical information, which are merged with physical info...

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...

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 sig...

This publication presents a robust and efficient approach for fully CAD-integrated analyses of solids, which aims to reduce the current modeling effort for static and transient problems, including implicit and explicit dynamic simulations. Generating high-quality finite element meshes of solid structures is still a time- and labor-intensive process...

We present various advances in computational wind engineering showcased on the Olympic Stadium in Munich, with the occasion of its 50-year anniversary of the official inauguration. This landmark building has been a motivator of technology since its inception, now influencing and pushing numerical tools to its limits. We especially focus on the effo...

We present the recorded values of certain numerical parameters when carrying out CFD simulations using a stabilized FEM formulation. It is of special interest to view these in the context of different geometric scales, particularly for high Reynolds numbers. Specifically, the ranges for y + and the CFL numbers are addressed, with the aim of accurat...

The present document analyses the flutter response of a double-deck bridge cross-section that allows the rotation of each part around their own centre. The results show that, depending on the natural frequency of the new distortional mode, the critical flutter wind speed can be manipulated until the point where the cross-section is completely stabl...

Algorithmic differentiation is used to analyse the interaction between input and output parameters of arbitrary computational models. We discuss the application of algorithmic differentiation at the interface between architecture and civil engineering in the field of CAD-integrated structural analysis and form finding.

Executable Digital Twins (xDTs) assist maintenance engineers by calculating current and future health status of physical assets based on operational conditions. In xDTs, the simulation describes the ideal physical behavior of the system, whereas the real data from sensors assist in updating the xDTs following the changes to the physical asset. We i...

We present various aspects of numerical modeling and simulation arising from the main focus areas of the Chair of Structural Analysis at the Technical University of Munich. These include several considerations on the load-bearing behavior of lightweight structures, which are best associated with and demonstrated on the Olympic Stadium in Munich. Th...

Reducing the intensity of wind excitation via aerodynamic shape modification is a major strategy to mitigate the reaction forces on supertall buildings, reduce construction and maintenance costs, and improve the comfort of future occupants. To this end, computational fluid dynamics (CFD) combined with state-of-the-art stochastic optimization algori...

Mass-movement hazards involving fast and large soil deformation often include huge rocks or other significant obstacles increasing tremendously the risks for humans and infrastructures. Therefore, numerical investigations of such disasters are in high economic demand for prediction as well as for the design of countermeasures. Unfortunately, classi...

The St. Venant-Kirchhoff law is a widely used constitutive relation in engineering applications. However, its limitation to small strains is frequently mentioned in the literature but rarely elaborated on. Therefore, we present a comprehensive study discussing the St. Venant-Kirchhoff law and its shortcomings in large stain regimes, focusing on com...

The efficiency of a Tuned Sloshing Damper (TSD) when mitigating wind-induced structural vibrations is investigated. We assessed the performance in terms of peak structural displacements and accelerations, compared to that of the Tuned Mass Damper (TMD). One load scenario considers oncoming gusts due to natural turbulence, whereas the other assumes...

The latest updates on the Vertex Morphing technique for large optimization problems are shown in this work. Discussions about the challenges of node-based shape optimization in academic and industrial applications are included. The adaptive Vertex Morphing technique is demonstrated, which is easy to use in practice and allows the full exploitation...

We introduce a novel hybrid methodology that combines classical finite element methods (FEM) with neural networks to create a well-performing and generalizable surrogate model for forward and inverse problems. The residual from finite element methods and custom loss functions from neural networks are merged to form the algorithm. The Finite Element...

We introduce a novel hybrid methodology combining classical finite element methods (FEM) with neural networks to create a well-performing and generalizable surrogate model for forward and inverse problems. The residual from finite element methods and custom loss functions from neural networks are merged to form the algorithm. The Finite Element Met...

Reducing the intensity of wind excitation via aerodynamic shape modification is a major strategy to mitigate the reaction forces on supertall buildings, reduce construction and maintenance costs, and improve the comfort of future occupants. To this end, computational fluid dynamics (CFD) combined with state-of-the-art stochastic optimization algori...

p>This paper is about sensitivity analysis and discusses how computational approaches like adjoint sensitivity analysis can be adopted for structural analysis models which consider the construction stage process. It is also shown how the sensitivities can be visualized by sensitivity maps and how these can significantly support the use of sensitivi...

p>Coda wave interferometry is an ultrasound-based possible candidate for structural health monitoring of concrete structures. It is based on a correlation evaluation of two ultrasonic signals. A perturbation, e.g., cracks in the medium are causing changes in the signal. The correlation development over the signal’s length is very characteristic for...

In this paper, load step reduction techniques are investigated for adjoint sensitivity analysis of path-dependent nonlinear finite element systems. In particular, the focus is on finite strain elastoplasticity with typical hardening models. The aim is to reduce the computational cost in the adjoint sensitivity implementation. The adjoint sensitivit...

In this study the isogeometric B-Rep mortar-based mapping method for geometry models stemming directly from Computer-Aided Design (CAD) is systematically augmented and applied to partitioned Fluid-Structure Interaction (FSI) simulations. Thus, the newly proposed methodology is applied to geometries described by their Boundary Representation (B-Rep)...

Engineering workflows are habitually split into a modelling phase and a consecutive analysis phase, which is primarily driven by the finite element method (FEM). However, bridging the gap between design and analysis remains a sophisticated problem and may consume a vast amount of computational as well as manual operations, especially in highly iter...

Rockfall protection systems are highly flexible structures that can absorb large amounts of energy. Compared to rigid protection structures, these structures undergo large deformations upon impact and thus result in lower braking accelerations. This leads to an effective transfer of the load. Previous works have shown that the partly highly complic...

Reinforced concrete is a widely used construction material in the building industry. With the increasing age of structures and higher loads there is an immense demand for structural health monitoring of built infrastructure. Coda wave interferometry is a possible candidate for damage detection in concrete whose applicability is demonstrated in this...

We present a consistent and efficient approach to the formulation of geometric nonlinear finite elements for isogeometric analysis (IGA) and isogeometric B-Rep analysis (IBRA) based on the adjoint method. IGA elements are computationally expensive, especially for high polynomial degrees. Using the method presented here enables us to reduce this dis...

Vertex morphing parametrization in combination with node-based shape optimization has proven to be invaluable in improving the initial engineering designs as it offers the largest possible design space. In this contribution, these optimization procedures were applied to additively manufactured components with the aim to improve their mechanical pro...

Attenuator barriers, in contrast to conventional safety nets, tend to smoothly guide impacting rocks instead of absorbing large amounts of strain energy arresting them. It has been shown that the rock's rotation plays an important role in the bearing capacity of these systems. Although experimental tests have to be conducted to gain a detailed insi...

In node-based shape optimization, there are a vast amount of design parameters, and the objectives, as well as the physical constraints, are non-linear in state and design. Robust optimization algorithms are required. The methods of feasible directions are widely used in practical optimization problems and know to be quite robust. A subclass of the...

There is a significant tendency in the industry for automation of the engineering design process. This requires the capability of analyzing an existing design and proposing or ideally generating an optimal design using numerical optimization. In this context, efficient and robust realization of such a framework for numerical shape optimization is o...

A numerical analysis is validated against a Swiss Federal Commission for Technology and Innovation (CTI)—frame impact experiment conducted by the Swiss Company Geobrugg. The discrete element method is used to simulate the impacting object, while the highly nonlinear structural response is analysed with the finite element method. Both methods are co...

The penalty method has proven to be a well-suited approach for the application of coupling and boundary conditions on (trimmed) multi-patch NURBS shell structures within isogeometric analysis. Beside its favorable simplicity and efficiency, the main challenge is the appropriate choice of the underlying penalty factor — choosing the penalty factor t...

Der Beitrag handelt von der computergestützten Sensitivitätsanalyse, mit welcher eine systematische Bewertung der Empfindlichkeit von Antwortgrößen eines statischen Systems bei variierenden Modellparametern möglich ist. Konkret wird gezeigt, wie zur Berechnung von Sensitivitäten die Technik der Einflusslinien verallgemeinert werden kann. Die vorges...