@article{TarabenMorgenthal, author = {Taraben, Jakob and Morgenthal, Guido}, title = {Integration and Comparison Methods for Multitemporal Image-Based 2D Annotations in Linked 3D Building Documentation}, series = {Remote Sensing}, volume = {2022}, journal = {Remote Sensing}, number = {Volume 14, issue 9, article 2286}, publisher = {MDPI}, address = {Basel}, doi = {10.3390/rs14092286}, url = {http://nbn-resolving.de/urn:nbn:de:gbv:wim2-20220513-46488}, pages = {1 -- 20}, abstract = {Data acquisition systems and methods to capture high-resolution images or reconstruct 3D point clouds of existing structures are an effective way to document their as-is condition. These methods enable a detailed analysis of building surfaces, providing precise 3D representations. However, for the condition assessment and documentation, damages are mainly annotated in 2D representations, such as images, orthophotos, or technical drawings, which do not allow for the application of a 3D workflow or automated comparisons of multitemporal datasets. In the available software for building heritage data management and analysis, a wide range of annotation and evaluation functions are available, but they also lack integrated post-processing methods and systematic workflows. The article presents novel methods developed to facilitate such automated 3D workflows and validates them on a small historic church building in Thuringia, Germany. Post-processing steps using photogrammetric 3D reconstruction data along with imagery were implemented, which show the possibilities of integrating 2D annotations into 3D documentations. Further, the application of voxel-based methods on the dataset enables the evaluation of geometrical changes of multitemporal annotations in different states and the assignment to elements of scans or building models. The proposed workflow also highlights the potential of these methods for condition assessment and planning of restoration work, as well as the possibility to represent the analysis results in standardised building model formats.}, subject = {Bauwesen}, language = {en} } @article{KavrakovKareemMorgenthal, author = {Kavrakov, Igor and Kareem, Ahsan and Morgenthal, Guido}, title = {Comparison Metrics for Time-histories: Application to Bridge Aerodynamics}, doi = {10.25643/bauhaus-universitaet.4186}, url = {http://nbn-resolving.de/urn:nbn:de:gbv:wim2-20200625-41863}, pages = {28}, abstract = {Wind effects can be critical for the design of lifelines such as long-span bridges. The existence of a significant number of aerodynamic force models, used to assess the performance of bridges, poses an important question regarding their comparison and validation. This study utilizes a unified set of metrics for a quantitative comparison of time-histories in bridge aerodynamics with a host of characteristics. Accordingly, nine comparison metrics are included to quantify the discrepancies in local and global signal features such as phase, time-varying frequency and magnitude content, probability density, nonstationarity and nonlinearity. Among these, seven metrics available in the literature are introduced after recasting them for time-histories associated with bridge aerodynamics. Two additional metrics are established to overcome the shortcomings of the existing metrics. The performance of the comparison metrics is first assessed using generic signals with prescribed signal features. Subsequently, the metrics are applied to a practical example from bridge aerodynamics to quantify the discrepancies in the aerodynamic forces and response based on numerical and semi-analytical aerodynamic models. In this context, it is demonstrated how a discussion based on the set of comparison metrics presented here can aid a model evaluation by offering deeper insight. The outcome of the study is intended to provide a framework for quantitative comparison and validation of aerodynamic models based on the underlying physics of fluid-structure interaction. Immediate further applications are expected for the comparison of time-histories that are simulated by data-driven approaches.}, subject = {Ingenieurwissenschaften}, language = {en} } @unpublished{AbbasKavrakovMorgenthaletal., author = {Abbas, Tajammal and Kavrakov, Igor and Morgenthal, Guido and Lahmer, Tom}, title = {Prediction of aeroelastic response of bridge decks using artificial neural networks}, doi = {10.25643/bauhaus-universitaet.4097}, url = {http://nbn-resolving.de/urn:nbn:de:gbv:wim2-20200225-40974}, abstract = {The assessment of wind-induced vibrations is considered vital for the design of long-span bridges. The aim of this research is to develop a methodological framework for robust and efficient prediction strategies for complex aerodynamic phenomena using hybrid models that employ numerical analyses as well as meta-models. Here, an approach to predict motion-induced aerodynamic forces is developed using artificial neural network (ANN). The ANN is implemented in the classical formulation and trained with a comprehensive dataset which is obtained from computational fluid dynamics forced vibration simulations. The input to the ANN is the response time histories of a bridge section, whereas the output is the motion-induced forces. The developed ANN has been tested for training and test data of different cross section geometries which provide promising predictions. The prediction is also performed for an ambient response input with multiple frequencies. Moreover, the trained ANN for aerodynamic forcing is coupled with the structural model to perform fully-coupled fluid--structure interaction analysis to determine the aeroelastic instability limit. The sensitivity of the ANN parameters to the model prediction quality and the efficiency has also been highlighted. The proposed methodology has wide application in the analysis and design of long-span bridges.}, subject = {Aerodynamik}, language = {en} } @unpublished{KavrakovMorgenthal, author = {Kavrakov, Igor and Morgenthal, Guido}, title = {A synergistic study of a CFD and semi-analytical models for aeroelastic analysis of bridges in turbulent wind conditions}, doi = {10.25643/bauhaus-universitaet.4087}, url = {http://nbn-resolving.de/urn:nbn:de:gbv:wim2-20200206-40873}, abstract = {Long-span bridges are prone to wind-induced vibrations. Therefore, a reliable representation of the aerodynamic forces acting on a bridge deck is of a major significance for the design of such structures. This paper presents a systematic study of the two-dimensional (2D) fluid-structure interaction of a bridge deck under smooth and turbulent wind conditions. Aerodynamic forces are modeled by two approaches: a computational fluid dynamics (CFD) model and six semi-analytical models. The vortex particle method is utilized for the CFD model and the free-stream turbulence is introduced by seeding vortex particles upstream of the deck with prescribed spectral characteristics. The employed semi-analytical models are based on the quasi-steady and linear unsteady assumptions and aerodynamic coefficients obtained from CFD analyses. The underlying assumptions of the semi-analytical aerodynamic models are used to interpret the results of buffeting forces and aeroelastic response due to a free-stream turbulence in comparison with the CFD model. Extensive discussions are provided to analyze the effect of linear fluid memory and quasi-steady nonlinearity from a CFD perspective. The outcome of the analyses indicates that the fluid memory is a governing effect in the buffeting forces and aeroelastic response, while the effect of the nonlinearity is overestimated by the quasi-steady models. Finally, flutter analyses are performed and the obtained critical velocities are further compared with wind tunnel results, followed by a brief examination of the post-flutter behavior. The results of this study provide a deeper understanding of the extent of which the applied models are able to replicate the physical processes for fluid-structure interaction phenomena in bridge aerodynamics and aeroelasticity.}, subject = {Ingenieurwissenschaften}, language = {en} } @unpublished{KavrakovMorgenthal, author = {Kavrakov, Igor and Morgenthal, Guido}, title = {Aeroelastic analyses of bridges using a Pseudo-3D vortex method and velocity-based synthetic turbulence generation}, doi = {10.25643/bauhaus-universitaet.4086}, url = {http://nbn-resolving.de/urn:nbn:de:gbv:wim2-20200206-40864}, abstract = {The accurate representation of aerodynamic forces is essential for a safe, yet reasonable design of long-span bridges subjected to wind effects. In this paper, a novel extension of the Pseudo-three-dimensional Vortex Particle Method (Pseudo-3D VPM) is presented for Computational Fluid Dynamics (CFD) buffeting analysis of line-like structures. This extension entails an introduction of free-stream turbulent fluctuations, based on the velocity-based turbulence generation. The aerodynamic response of a long-span bridge is obtained by subjecting the 3D dynamic representation of the structure to correlated free-stream turbulence in two-dimensional (2D) fluid planes, which are positioned along the bridge deck. The span-wise correlation of the free-stream turbulence between the 2D fluid planes is established based on Taylor's hypothesis of frozen turbulence. Moreover, the application of the laminar Pseudo-3D VPM is extended to a multimode flutter analysis. Finally, the structural response from the Pseudo-3D flutter and buffeting analyses is verified with the response, computed using the semi-analytical linear unsteady model in the time-domain. Meaningful merits of the turbulent Pseudo-3D VPM with respect to the linear unsteady model are the consideration of the 2D aerodynamic nonlinearity, nonlinear fluid memory, vortex shedding and local non-stationary turbulence effects in the aerodynamic forces. The good agreement of the responses for the two models in the 3D analyses demonstrates the applicability of the Pseudo-3D VPM for aeroelastic analyses of line-like structures under turbulent and laminar free-stream conditions.}, subject = {Bridge}, language = {en} } @unpublished{KavrakovArgentiniOmarinietal., author = {Kavrakov, Igor and Argentini, Tommaso and Omarini, Simone and Rocchi, Daniele and Morgenthal, Guido}, title = {Determination of complex aerodynamic admittance of bridge decks under deterministic gusts using the Vortex Particle Method}, doi = {10.25643/bauhaus-universitaet.4088}, url = {http://nbn-resolving.de/urn:nbn:de:gbv:wim2-20200206-40883}, abstract = {Long-span bridges are prone to wind-induced vibrations. Therefore, a reliable representation of the aerodynamic forces acting on a bridge deck is of a major significance for the design of such structures. This paper presents a systematic study of the two-dimensional (2D) fluid-structure interaction of a bridge deck under smooth and turbulent wind conditions. Aerodynamic forces are modeled by two approaches: a computational fluid dynamics (CFD) model and six semi-analytical models. The vortex particle method is utilized for the CFD model and the free-stream turbulence is introduced by seeding vortex particles upstream of the deck with prescribed spectral characteristics. The employed semi-analytical models are based on the quasi-steady and linear unsteady assumptions and aerodynamic coefficients obtained from CFD analyses. The underlying assumptions of the semi-analytical aerodynamic models are used to interpret the results of buffeting forces and aeroelastic response due to a free-stream turbulence in comparison with the CFD model. Extensive discussions are provided to analyze the effect of linear fluid memory and quasi-steady nonlinearity from a CFD perspective. The outcome of the analyses indicates that the fluid memory is a governing effect in the buffeting forces and aeroelastic response, while the effect of the nonlinearity is overestimated by the quasi-steady models. Finally, flutter analyses are performed and the obtained critical velocities are further compared with wind tunnel results, followed by a brief examination of the post-flutter behavior. The results of this study provide a deeper understanding of the extent of which the applied models are able to replicate the physical processes for fluid-structure interaction phenomena in bridge aerodynamics and aeroelasticity.}, subject = {Bridge}, language = {en} } @inproceedings{VilceanuAbrahamczykMorgenthal, author = {V{\^i}lceanu, Victor and Abrahamczyk, Lars and Morgenthal, Guido}, title = {Nonlinear Analysis of Structures: Wind Induced Vibrations}, doi = {10.25643/bauhaus-universitaet.4033}, url = {http://nbn-resolving.de/urn:nbn:de:gbv:wim2-20191122-40337}, pages = {183}, abstract = {The proceedings at hand are the result of the International Master Course Module: "Nonlinear Analysis of Structures: Wind Induced Vibrations" held at the Faculty of Civil Engineering at Bauhaus-University Weimar, Germany in the summer semester 2019 (April - August). This material summarizes the results of the project work done throughout the semester, provides an overview of the topic, as well as impressions from the accompanying programme. Wind Engineering is a particular field of Civil Engineering that evaluates the resistance of structures caused by wind loads. Bridges, high-rise buildings, chimneys and telecommunication towers might be susceptible to wind vibrations due to their increased flexibility, therefore a special design is carried for this aspect. Advancement in technology and scientific studies permit us doing research at small scale for more accurate analyses. Therefore scaled models of real structures are built and tested for various construction scenarios. These models are placed in wind tunnels where experiments are conducted to determine parameters such as: critical wind speeds for bridge decks, static wind coefficients and forces for buildings or bridges. The objective of the course was to offer insight to the students into the assessment of long-span cable-supported bridges and high-rise buildings under wind excitation. The participating students worked in interdisciplinary teams to increase their knowledge in the understanding and influences on the behaviour of wind-sensitive structures.}, subject = {Ingenieurbau}, language = {en} } @article{MorgenthalEickRauetal., author = {Morgenthal, Guido and Eick, Jan Frederick and Rau, Sebastian and Taraben, Jakob}, title = {Wireless Sensor Networks Composed of Standard Microcomputers and Smartphones for Applications in Structural Health Monitoring}, series = {Sensors - Special Issue Selected Papers from 7th Asia-Pacific Workshop on Structural Health Monitoring}, volume = {2019}, journal = {Sensors - Special Issue Selected Papers from 7th Asia-Pacific Workshop on Structural Health Monitoring}, number = {Volume 19, Issue 9, 2070}, publisher = {MDPI}, doi = {10.3390/s19092070}, url = {http://nbn-resolving.de/urn:nbn:de:gbv:wim2-20190514-39123}, pages = {22}, abstract = {Wireless sensor networks have attracted great attention for applications in structural health monitoring due to their ease of use, flexibility of deployment, and cost-effectiveness. This paper presents a software framework for WiFi-based wireless sensor networks composed of low-cost mass market single-board computers. A number of specific system-level software components were developed to enable robust data acquisition, data processing, sensor network communication, and timing with a focus on structural health monitoring (SHM) applications. The framework was validated on Raspberry Pi computers, and its performance was studied in detail. The paper presents several characteristics of the measurement quality such as sampling accuracy and time synchronization and discusses the specific limitations of the system. The implementation includes a complementary smartphone application that is utilized for data acquisition, visualization, and analysis. A prototypical implementation further demonstrates the feasibility of integrating smartphones as data acquisition nodes into the network, utilizing their internal sensors. The measurement system was employed in several monitoring campaigns, three of which are documented in detail. The suitability of the system is evaluated based on comparisons of target quantities with reference measurements. The results indicate that the presented system can robustly achieve a measurement performance commensurate with that required in many typical SHM tasks such as modal identification. As such, it represents a cost-effective alternative to more traditional monitoring solutions.}, subject = {Structural Health Monitoring}, language = {en} } @article{KavrakovLegatiukGuerlebecketal., author = {Kavrakov, Igor and Legatiuk, Dmitrii and G{\"u}rlebeck, Klaus and Morgenthal, Guido}, title = {A categorical perspective towards aerodynamic models for aeroelastic analyses of bridge decks}, series = {Royal Society Open Science}, journal = {Royal Society Open Science}, number = {Volume 6, Issue 3}, doi = {/10.1098/rsos.181848}, url = {http://nbn-resolving.de/urn:nbn:de:gbv:wim2-20190314-38656}, pages = {20}, abstract = {Reliable modelling in structural engineering is crucial for the serviceability and safety of structures. A huge variety of aerodynamic models for aeroelastic analyses of bridges poses natural questions on their complexity and thus, quality. Moreover, a direct comparison of aerodynamic models is typically either not possible or senseless, as the models can be based on very different physical assumptions. Therefore, to address the question of principal comparability and complexity of models, a more abstract approach, accounting for the effect of basic physical assumptions, is necessary. This paper presents an application of a recently introduced category theory-based modelling approach to a diverse set of models from bridge aerodynamics. Initially, the categorical approach is extended to allow an adequate description of aerodynamic models. Complexity of the selected aerodynamic models is evaluated, based on which model comparability is established. Finally, the utility of the approach for model comparison and characterisation is demonstrated on an illustrative example from bridge aeroelasticity. The outcome of this study is intended to serve as an alternative framework for model comparison and impact future model assessment studies of mathematical models for engineering applications.}, subject = {Br{\"u}cke}, language = {en} } @article{BenzTarabenLichtenheldetal., author = {Benz, Alexander and Taraben, Jakob and Lichtenheld, Thomas and Morgenthal, Guido and V{\"o}lker, Conrad}, title = {Thermisch-energetische Geb{\"a}udesimulation auf Basis eines Bauwerksinformationsmodells}, series = {Bauphysik}, journal = {Bauphysik}, number = {40, Heft 2}, doi = {10.25643/bauhaus-universitaet.3835}, url = {http://nbn-resolving.de/urn:nbn:de:gbv:wim2-20181221-38354}, pages = {61 -- 67}, abstract = {F{\"u}r eine Absch{\"a}tzung des Heizw{\"a}rmebedarfs von Geb{\"a}uden und Quartieren k{\"o}nnen thermisch-energetische Simulationen eingesetzt werden. Grundlage dieser Simulationen sind geometrische und physikalische Geb{\"a}udemodelle. Die Erstellung des geometrischen Modells erfolgt in der Regel auf Basis von Baupl{\"a}nen oder Vor-Ort-Begehungen, was mit einem großen Recherche- und Modellierungsaufwand verbunden ist. Sp{\"a}tere bauliche Ver{\"a}nderungen des Geb{\"a}udes m{\"u}ssen h{\"a}ufig manuell in das Modell eingearbeitet werden, was den Arbeitsaufwand zus{\"a}tzlich erh{\"o}ht. Das physikalische Modell stellt die Menge an Parametern und Randbedingungen dar, welche durch Materialeigenschaften, Lage und Umgebungs-einfl{\"u}sse gegeben sind. Die Verkn{\"u}pfung beider Modelle wird innerhalb der entsprechenden Simulations-software realisiert und ist meist nicht in andere Softwareprodukte {\"u}berf{\"u}hrbar. Mithilfe des Building Information Modeling (BIM) k{\"o}nnen Simulationsdaten sowohl konsistent gespeichert als auch {\"u}ber Schnittstellen mit entsprechenden Anwendungen ausgetauscht werden. Hierf{\"u}r wird eine Methode vorgestellt, die thermisch-energetische Simulationen auf Basis des standardisierten {\"U}bergabe-formats Industry Foundation Classes (IFC) inklusive anschließender Auswertungen erm{\"o}glicht. Dabei werden geometrische und physikalische Parameter direkt aus einem {\"u}ber den gesamten Lebenszyklus aktuellen Geb{\"a}udemodell extrahiert und an die Simulation {\"u}bergeben. Dies beschleunigt den Simulations-prozess hinsichtlich der Geb{\"a}udemodellierung und nach sp{\"a}teren baulichen Ver{\"a}nderungen. Die erarbeite-te Methode beruht hierbei auf einfachen Modellierungskonventionen bei der Erstellung des Bauwerksinformationsmodells und stellt eine vollst{\"a}ndige {\"U}bertragbarkeit der Eingangs- und Ausgangswerte sicher. Thermal building simulation based on BIM-models. Thermal energetic simulations are used for the estimation of the heating demand of buildings and districts. These simulations are based on building models containing geometrical and physical information. The creation of geometrical models is usually based on existing construction plans or in situ assessments which demand a comparatively big effort of investigation and modeling. Alterations, which are later applied to the structure, request manual changes of the related model, which increases the effort additionally. The physical model represents the total amount of parameters and boundary conditions that are influenced by material properties, location and environmental influences on the building. The link between both models is realized within the correspondent simulation soft-ware and is usually not transferable to other software products. By Applying Building Information Modeling (BIM) simulation data is stored consistently and an exchange to other software is enabled. Therefore, a method which allows a thermal energetic simulation based on the exchange format Industry Foundation Classes (IFC) including an evaluation is presented. All geometrical and physical information are extracted directly from the building model that is kept up-to-date during its life cycle and transferred to the simulation. This accelerates the simulation process regarding the geometrical modeling and adjustments after later changes of the building. The developed method is based on simple conventions for the creation of the building model and ensures a complete transfer of all simulation data.}, subject = {Building Information Modeling}, language = {de} }