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Item type:Publication, Access status: with files , Locking-free energy-based physics-informed neural networks for shear-deformable beams and platesPhysics-informed neural networks (PINNs) embed governing equations into the training objective and provide a data-efficient machine-learning framework for problems governed by partial differential equations (PDEs). When applying the PINN framework to stiff PDEs, a deterioration of training speed and accuracy can be observed. From a mathematical perspective, the high ratio of coefficients in a stiff PDE is the source of locking effects, known from other discretization schemes. This work investigates transverse shear locking in PINNs for Timoshenko beams and Reissner–Mindlin plates and proposes effective mitigation strategies. We implement energy-based PINNs using different parametrizations of the kinematics: the standard parametrization and hierarchic parametrizations. Our results demonstrate that standard approaches exhibit severe locking behavior, with training speed deteriorating significantly as the slenderness increases. Based on an in-depth study of the training dynamics, we identify the causes of transverse shear locking in PINNs considered in this work. To address them, we adapt hierarchic formulations from structural mechanics to the PINN framework by: (1) using hierarchic formulations that directly parametrize the shear deformation, (2) employing separate neural networks for each primary variable to isolate the trainable parameters, and (3) introducing a slenderness-dependent scaling factor for the shear deformation variable to balance the gradients of the energy terms for training. The proposed method achieves fast, slenderness-independent training and convergence for both beam and plate problems for all variables of interest. The method is developed using energy-based forward-solving PINNs, and its transfer to related PDE-loss-based learning frameworks is illustrated with a parametric PINN.Publicationtype: Journal Article16 28 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Vergleich numerischer Analyse- und Diskretisierungsverfahren für instabilitätsgefährdete SchalentragwerkeNumerische Stabilitätsanalysen dünner Schalentragwerke sind anspruchsvoll und rechenintensiv. Die Wahl geeigneter Imperfektionen ist nach EC3 nicht eindeutig geregelt und fehleranfällig. Der vorliegende Beitrag diskutiert den Einfluss eigenformaffiner Imperfektionen auf die numerische Traglast von Schalentragwerken. Zudem werden unterschiedliche Analyse- und Diskretisierungsverfahren hinsichtlich Genauigkeit und Effizienz verglichen. Im vorliegenden Beitrag werden Zwischenergebnisse aus umfangreichen, systematischen numerischen Konvergenz- und Parameterstudien vorgestellt und diskutiert.Publicationtype: Conference Paper27 12 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Verbesserung der Effizienz dynamischer Simulationen mithilfe hierarchischer Platten- und Schalenformulierungen(Technische Universität Dresden, 2026-05-26); ; Die Stabilität expliziter Zeitintegrationsverfahren ist durch eine kritische Zeitschrittweite begrenzt, die bei schubweichen Platten- und Schalenmodellen von der höchsten Frequenz der Querschubmoden abhängt. Um die kritische Zeitschrittweite zu erhöhen und damit die Rechenzeit zu verkürzen werden häufig Massenskalierungsmethoden verwendet. Eine Herausforderung ist dabei, einen guten Kompromiss zwischen Rechenzeit und Genauigkeit zu finden. Hierarchische Platten- und Schalenformulierungen, ursprünglich zur Vermeidung von Querschublocking entwickelt, ermöglichen eine selektive Skalierung der Trägheit der Querschubmoden ohne die Genauigkeit der Biegemoden wesentlich zu beeinträchtigen. Diese bereits als intrinsisch lockingfrei bekannten hierarchischen Formulierungen erlauben also auch eine intrinsisch selektive Massenskalierung.Publicationtype: Conference Paper21 12 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , The Role of Wind Velocity in Saline Water Evaporation from Porous Media and Surface Salt Crystallization Dynamics(2025-07-06); ; ; ; This study systematically investigates the effect of wind flow on evaporation dynamics and salt crystallization patterns in porous media. Well-controlled experiments were conducted in a laboratory wind tunnel, where the surface of sand columns saturated with freshwater and NaCl solutions at concentrations of 10%, 15%, and 20% were subjected to wind flows of 0.5 and 5 m/s, corresponding to laminar and turbulent flow regimes, respectively. Mass loss measurements from the samples, combined with optical imaging of their surfaces, revealed distinct evaporation dynamics and crystallization patterns. We observed that the interaction between intermittent turbulent airflow and evolving salt crystals on the surface resulted in a relatively uniform crystallization pattern. In contrast, under laminar airflow conditions, salt crystal nucleation and formation primarily occurred at the leading edge of the sample, particularly at lower salt concentrations. We further investigated the impact of enhanced evaporative mass loss in the presence of wind on crystallization dynamics by quantifying the crystal coverage and its lateral extent on the surface. Under turbulent flow conditions, we observed that full coverage of the surface with salt crystals requires 2 to 3 times higher evaporative losses in 10% NaCl sample relative to the 15% and 20% samples, respectively. These findings highlight the complex interplay between evaporation and crystallization processes under varying airflow conditions, thus offering valuable insight for improving hydrological and climatological modeling.Publicationtype: Journal Article32 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Selective mass scaling for Timoshenko beam and Mindlin plate elements based on the discrete strain gap method(Institute of Structural Analysis and Antiseismic Research National Technical University of Athens, 2025-06); ; ; The conditional stability of explicit time integration algorithms limits the critical time step size, which depends on the highest natural frequency of the discretized problem. For shear deformable structural finite element formulations, efficiency is typically limited by the highest transverse shear frequencies. Selective mass scaling (SMS) methods aim at selectively scaling the high frequencies while preserving the important low frequency content. In particular, recent SMS concepts, which are inspired by the discrete strain gap (DSG) method [1] and, thus, are denoted as DSGSMS concepts, result in effective and accurate methods, which naturally preserve both linear and angular momentum. In this contribution, we extend previous work on DSGSMS for shear deformable element formulations [2] with respect to several aspects. First, we perform a theoretical analysis of the DSGSMS method that provides new insight into spectral properties and analytical time step estimates. Second, we extend the DSGSMS method from Timoshenko beam elements to Mindlin plate elements. Third, we test the extended concept with respect to spectral accuracy and the transient behavior in explicit time integration.Publicationtype: Conference Paper52 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Selective mass scaling for Timoshenko beam and Mindlin plate elements based on the discrete strain gap methodPublicationtype: Conference Paper36 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , 36 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , The role of wind velocity in saline water evaporation from porous media and surface salt crystallization dynamicsSaline water evaporation from porous media with the corresponding surface salt crystallization patterns play a vital role in many environmental and engineering applications. While the impact of factors such as type and concentration of salt, particle size and angularity, and ambient temperature and humidity are relatively well characterized [1]–[3], the influence of wind and aerodynamic conditions on saline water evaporation and salt crystallization is not fully understood. We conducted a series of laboratory experiments in a wind tunnel to systematically investigate the effect of wind flow on saline water evaporation and dynamics of salt crystallization. Cylindrical sand columns (D: 5 cm – H: 20 cm) were placed in the test section of the wind tunnel. Surface of the samples were exposed to uniform mean wind velocities of 0.5 and 5 m/s. To keep samples fully saturated during the evaporation experiments, sand columns were supplied from Mariotte bottles containing 10, 15, and 20% NaCl solutions. Evaporation rates were monitored by measuring mass losses from Mariotte bottles, while salt crystallization patterns were captured using an optical camera positioned above the surface of columns. Preliminary results indicate that variation in aerodynamic conditions and turbulence patterns, driven by changes in wind velocity and surface roughness (due to crystal growth), significantly alter evaporation rates and salt crystallization process. Distinct crystallization patterns were observed with variation of wind velocity with possible influences on the evaporative fluxes. Using the measured data, we will identify the key effects of air flow regimes coupled with the salt concentration on evaporative losses and the evolution of crystallized salts at the surface, which will be important for a wide range of environmental and hydrological applications.Publicationtype: Conference Paper11 16 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Intrinsically selective mass scaling with hierarchic plate formulationsThe critical time step in explicit time integration methods depends on the highest natural angular frequency of the discretized problem. For shear deformable beam, plate and shell formulations, efficiency is therefore typically limited by the highest transverse shear frequencies, which are mostly of minor importance for the structural response. Direct parametrization using transverse shear variables within hierarchic structural element formulations allows a selective scaling of transverse shear frequencies in a simple manner, while bending frequencies remain practically unaffected. In particular, the novel concept of intrinsically selective mass scaling (ISMS) results in an efficient method that features high accuracy and preserves both linear and angular momentum for both consistent and lumped mass matrices. In addition, ISMS preserves the diagonal structure of lumped mass matrices. Similar to the underlying intrinsically locking-free, hierarchic concept for shear deformable structural element formulations, ISMS retains its beneficial properties for any smooth discretization scheme. In this contribution, we extend recent research on ISMS for beam formulations to the case of shear deformable plate formulations. We test our novel concept with respect to accuracy and efficiency by means of selected numerical experiments. We study both frequency spectra and the transient behavior in explicit time integration. To demonstrate the generality of ISMS, exemplarily both isogeometric discretizations based on B-splines and meshfree discretizations using local maximum-entropy approximants are investigated.Publicationtype: Journal Article29 50 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Neuartige selektive Massenskalierungsmethoden für transiente Analysen dünnwandiger Strukturen mit Volumenelementen und expliziter Zeitintegration(Technische Universität Hamburg, Institut für Digitales und Autonomes Bauen, 2024-09-18)Die Effizienz transienter Analysen unter Verwendung expliziter Zeitintegrationsverfahren ist durch die kritische Zeitschrittweite bestimmt. Die höchsten Eigenfrequenzen des diskreten Systems begrenzen die erlaubte kritische Zeitschrittweite, während sie meist nur einen geringen Einfluss auf das tatsächliche Strukturverhalten haben. Methoden der selektiven Massenskalierung (SMS) zielen darauf ab, die höchsten Eigenfrequenzen zu reduzieren, während die relevanten niedrigen Eigenfrequenzen idealerweise unverändert bleiben. Die meisten der bestehenden SMS-Methoden wurden für Volumen- oder Volumenschalenelemente entwickelt und darauf ausgelegt, dass die translatorische Trägheit und damit der Impuls erhalten bleibt. In diesem Beitrag werden neuartige SMS-Methoden vorgestellt, die intrinsisch impuls- und drehimpulserhaltend sind und sich durch eine hohe Genauigkeit auszeichnen. Die neuen SMS-Methoden werden hinsichtlich Genauigkeit und Effizienz untersucht und mit dem Stand der Technik verglichen.Publicationtype: Conference Paper14 69