TY - JOUR A1 - Morgenthal, Guido A1 - Eick, Jan Frederick A1 - Rau, Sebastian A1 - Taraben, Jakob T1 - Wireless Sensor Networks Composed of Standard Microcomputers and Smartphones for Applications in Structural Health Monitoring JF - Sensors - Special Issue Selected Papers from 7th Asia-Pacific Workshop on Structural Health Monitoring N2 - 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. KW - Structural Health Monitoring KW - Mikrocomputer KW - Smartphone KW - Schwingungsmessung KW - Wireless sensor network KW - Raspberry Pi KW - Smartphones KW - Vibration measurements KW - OA-Publikationsfonds2019 Y1 - 2019 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:gbv:wim2-20190514-39123 UR - https://www.mdpi.com/1424-8220/19/9/2070 VL - 2019 IS - Volume 19, Issue 9, 2070 PB - MDPI ER - TY - JOUR A1 - Kavrakov, Igor A1 - Legatiuk, Dmitrii A1 - Gürlebeck, Klaus A1 - Morgenthal, Guido T1 - A categorical perspective towards aerodynamic models for aeroelastic analyses of bridge decks JF - Royal Society Open Science N2 - 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. KW - Brücke KW - Aerodynamik KW - Aeroelastizität KW - bridge KW - abstract modelling KW - category theory KW - bridge aerodynamics KW - bridge aeroelasticity KW - aerodynamic models KW - model complexity KW - OA-Publikationsfonds2019 Y1 - 2019 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:gbv:wim2-20190314-38656 UR - https://royalsocietypublishing.org/doi/10.1098/rsos.181848 IS - Volume 6, Issue 3 ER - TY - CHAP A1 - Vîlceanu, Victor A1 - Abrahamczyk, Lars A1 - Morgenthal, Guido T1 - Nonlinear Analysis of Structures: Wind Induced Vibrations N2 - 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. T3 - Schriftenreihe des Instituts für Konstruktiven Ingenieurbau - 0 KW - Ingenieurbau KW - Structural Engineering KW - wind-induced vibration KW - Konstruktiver Ingenieurbau KW - nonlinear analysis KW - Förderungsprogramm KW - Erasmus + Y1 - 2019 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:gbv:wim2-20191122-40337 ER - TY - INPR A1 - Kavrakov, Igor A1 - Argentini, Tommaso A1 - Omarini, Simone A1 - Rocchi, Daniele A1 - Morgenthal, Guido T1 - Determination of complex aerodynamic admittance of bridge decks under deterministic gusts using the Vortex Particle Method N2 - 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. KW - Bridge KW - Aerodynamik KW - Ingenieurwissenschaften KW - Aerodynamic admittance KW - Computational fluid dynamics KW - Vortex particle method KW - Buffeting KW - Long-span bridges Y1 - 2019 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:gbv:wim2-20200206-40883 N1 - This is the pre-peer reviewed version of the following article: https://www.sciencedirect.com/science/article/pii/S0167610519305719?via%3Dihub, which has been published in final form at https://doi.org/10.1016/j.jweia.2019.103971 ER -