@misc{HoeltkeBleicher, author = {H{\"o}ltke, Tim and Bleicher, Achim}, title = {Experimental and numerical investigations of a timber-concrete composite frame joint for high-rise buildings}, series = {Engineering Structures}, volume = {333}, journal = {Engineering Structures}, issn = {0141-0296}, doi = {10.1016/j.engstruct.2025.120034}, pages = {1 -- 21}, abstract = {This paper presents a recently developed joint for timber-concrete composite frames. The developed joint was studied in terms of its ability to transfer bending moments, normal and shear forces resulting in a frame structure under horizontal and vertical loads. Several aspects are taken into account during the development and manufacturing process such as the material-appropriate use and a simple assembly concept. A series of experimental full-scale tests, with extensive measurements, were conducted consisting of five test specimens to investigate the static properties of the joint construction. The focused properties are the bending and rotational capacity as well as a ductile beam-to-column connection. For all specimens beech laminated veneer lumber was used, varying the geometric dimensions of the column and composite beam as well as the concrete strength. In addition to the experimental investigations, a numerical model was developed and validated using local strains, global deformations and rotational stiffness. Relevant numerical input parameters, which were not determined experimentally, were investigated as part of a numerical parameter analysis.}, language = {en} } @misc{BleicherHoeltkeManfrecola, author = {Bleicher, Achim and H{\"o}ltke, Tim and Manfrecola, Johannes}, title = {Hybrid structures for tall buildings with hardwood LVL and concrete}, series = {IABSE Symposium 2025, Environmentally Friendly Technologies and Structures - Focusing on Sustainable Approaches, May 18-21, 2025, Tokyo, Japan}, journal = {IABSE Symposium 2025, Environmentally Friendly Technologies and Structures - Focusing on Sustainable Approaches, May 18-21, 2025, Tokyo, Japan}, publisher = {International Association For Bridge And Structural Engineering (IABSE)}, address = {Z{\"u}rich}, isbn = {978-3-85748-206-9}, doi = {10.2749/tokyo.2025.1927}, pages = {1927 -- 1934}, abstract = {New fire design approaches enable innovative load-bearing and bracing concepts for tall buildings made of timber. As a renewable building material, timber in combination with concrete is currently setting new heights and at the same time offers a high CO2 saving potential. Usually, timber-concrete composite structures are mainly used in the floor slabs to ensure sound insulation and fire protection. This paper presents a newly developed beam-to-column joint for timber-concrete composite frames, which has been studied in terms of its ability to transfer bending moments, normal and shear forces. A series of full-scale experimental tests were conducted to investigate the structural properties of the joint design. In addition, all specimens were analysed numerically to verify the load transfer mechanisms. As an overall result, the test specimens showed a ductile behaviour beyond their primary failure. Finally, hybrid multi-story frame systems with rigid beam-to-column connections can be used for structural bracing of mid-rise buildings and efficiently combined with an (excentric) core for high-rise buildings.}, language = {en} } @misc{FreymannSchauerBleicher, author = {Freymann, Konrad and Schauer, Thomas and Bleicher, Achim}, title = {Lifetime extension for steel railway bridges using additional damping : a case study for an existing bridge}, series = {IABSE Symposium 2025, Environmentally Friendly Technologies and Structures - Focusing on Sustainable Approaches, May 18-21, 2025, Tokyo, Japan}, journal = {IABSE Symposium 2025, Environmentally Friendly Technologies and Structures - Focusing on Sustainable Approaches, May 18-21, 2025, Tokyo, Japan}, publisher = {International Association For Bridge And Structural Engineering (IABSE)}, address = {Z{\"u}rich}, isbn = {978-3-85748-206-9}, doi = {10.2749/tokyo.2025.1885}, pages = {1885 -- 1893}, abstract = {Steel bridges as slender and highly articulated lightweight structures are exceedingly exposed to fatigue damage due to traffic. Especially railway traffic is causing significant stress variations, the material can only withstand a limited amplitude and number of stress cycles. This results in a reduced lifetime of the bridge. This paper gives an overview of the material behaviour of steel due to fatigue. The lifetime capacity of an existing bridge as reference is analysed according to the current state of technology based on a simplified FE-Model. Further, the potential for extending the lifespan by reducing the vibration cycles through additional damping is numerically investigated for the referred bridge. A possible direct correlation between fatigue-relevant stress and the remaining service life of the existing bridge is demonstrated.}, language = {en} } @misc{JirasekSchauerBleicher, author = {Jirasek, Robert and Schauer, Thomas and Bleicher, Achim}, title = {Linear parameter-varying output-feedback for active vibration control of an elastic kinetic roof structure with experimental validation}, series = {Engineering Structures}, volume = {307}, journal = {Engineering Structures}, issn = {0141-0296}, doi = {10.1016/j.engstruct.2024.117887}, pages = {1 -- 12}, abstract = {Elastic kinetics are an approach to design transformable lightweight structures with a stable transformation process. The transformation is realized through elastic bending of structural members by exploiting the compliant material behavior. This lightweight and flexible design comes at the cost of increased sensitivity to static and dynamic disturbances. However, most of the current research focuses on the principles of elastic kinetic transformation instead of effective disturbance mitigation. This work focuses on dynamic disturbance mitigation for such transformable lightweight structures using active control. Modeling and controller synthesis are performed in the linear parameter-varying (LPV) framework, since the dynamics of elastic kinetic structures are transformation-state dependent due to geometric nonlinearities. Based on an LPV model in a grid-based representation, an LPV output-feedback control can be designed and synthesized via a gridding approach. This methodology is experimentally tested and validated for the example of an active hybrid roof structure prototype.}, language = {en} } @techreport{HoeltkeManfrecolaBleicher, author = {H{\"o}ltke, Tim and Manfrecola, Johannes and Bleicher, Achim}, title = {Biegetragf{\"a}hige Holz-Beton-Verbundknoten aus Baubuche zur Aussteifung von Hochbauten}, volume = {78/2024}, address = {Bonn}, issn = {1868-0097}, pages = {85}, abstract = {Das hier bearbeitete Forschungsprojekt leistet einen ersten Beitrag zur Entwicklung von biegetragf{\"a}higen Holz-Beton-Verbundknoten in Rahmentragwerken zur Aussteifung von Hochbauten. Rahmentragwerke liefern architektonische Vorteile in der Grundriss- und Fassadengestaltung von Geb{\"a}uden durch den Wegfall von aussteifenden Verb{\"a}nden und Schubw{\"a}nden und sind damit besonders f{\"u}r eine sp{\"a}tere Umnutzung geeignet. Die Entwicklung der hier betrachteten Rahmenknoten basiert auf dem Lastabtrag mehrfeldriger und mehrgeschossiger ebener Rahmensysteme. Der lokale Lastabtrag in der Knotenkonstruktion konnte im ersten Schritt des Projektes auf Grundlage von Stabwerksmodellen visualisiert und nachgewiesen werden. Es wurde darauf geachtet, die verwendeten Materialien - Holz, Beton und Stahl - werkstoffgerecht einzusetzen, um eine gr{\"o}ßtm{\"o}gliche Tragf{\"a}higkeit zu erzielen. Rahmentragwerke gelten aufgrund der konzentrierten Lastabtragung in den Knoten als hochbeanspruchte Tragwerke. Daher wurde ein hochfestes Buchenfurnierschichtholz der Firma Pollmeier Furnierschichtholz GmbH verwendet, welches eine etwa 3-mal h{\"o}here Biegefestigkeit als konventionelle Nadelh{\"o}lzer aufweist. Zur Untersuchung der statischen Eigenschaften wie Lastabtragungsmechanismen, Grenztragf{\"a}higkeiten und Rotationssteifigkeiten wurde eine Versuchsserie mit insgesamt 6 Versuchsk{\"o}rpern im realit{\"a}tsnahen Maßstab erarbeitet. Die einzelnen Versuchsk{\"o}rper unterscheiden sich in den geometrischen Abmessungen der Riegelquerschnitte, im St{\"u}tzenanschluss und der Festigkeit des Verbundpartners Beton. Zur besseren Vergleichbarkeit wurden die Betone in der Forschungs- und Materialpr{\"u}fanstalt (FMPA) der BTU Cottbus-Senftenberg selbst hergestellt, mit dem Ziel vergleichbare Werkstoffeigenschaften zwischen den einzelnen Versuchsk{\"o}rpern zu erzielen bei denen der Beton nicht der Variationsparameter ist. Im Sinne einer nachhaltigen Kreislaufwirtschaft wurde auch untersucht, ob sich Recyclingbeton f{\"u}r die statischen Anforderungen in der Rahmenkonstruktion eignet. Die einzelnen Versuchsk{\"o}rper wurden zum weiteren Erkenntnisgewinn numerisch mit Hilfe der FE-Software Ansys Workbench untersucht. In den r{\"a}umlichen Modellen wurden, f{\"u}r m{\"o}glichst realit{\"a}tsnahe Simulationen der experimentellen Versuche, die materiellen und kontaktbedingten Nichtlinearit{\"a}ten ber{\"u}cksichtigt. Die numerischen Ergebnisse wurden anschließend anhand der experimentellen Ergebnisse validiert. Die Herstellung der Versuchsk{\"o}rper und die experimentelle Versuchsdurchf{\"u}hrung erfolgte in der FMPA. Auf Basis der numerischen und experimentellen Erkenntnisse konnten anschließend maßgebende Versagensstellen identifiziert und ein analytisches Konzept zur Bestimmung der Tragf{\"a}higkeit erarbeitet werden. Auch wurden signifikante Verformungskomponenten benannt und zu einem analytischen Gesamtfedermodell der Knotenkonstruktion nach Vorbild der Komponentenmethode aus dem Stahl- und Stahl-Beton-Verbundbau zusammengef{\"u}hrt. Durch ein erstes Gesamtfedermodell kann aus den Verformungen der Komponenten die Rotationssteifigkeit berechnet werden. Das analytische Gesamtfedermodell wurden abschließend mit den experimentellen Ergebnissen validiert. Den Abschluss des Forschungsprojektes bilden Empfehlungen zur Ausbildung duktiler Rahmenknoten im Holz-Beton-Verbundbau auf Grundlage der experimentellen, numerischen und analytischen Ergebnisse.}, language = {de} } @incollection{FreymannSchauerBleicher, author = {Freymann, Konrad and Schauer, Thomas and Bleicher, Achim}, title = {Adaptive Doppelfassade zur Schwingungskontrolle}, series = {Beyond Transparency}, booktitle = {Beyond Transparency}, editor = {GmbH, Messe D{\"u}sseldorf}, publisher = {Messe D{\"u}sseldorf GmbH}, address = {D{\"u}sseldorf}, pages = {26 -- 26}, language = {de} } @misc{ZhangWulffWernickeetal., author = {Zhang, Yangwen and Wulff, Wulf and Wernicke, Laurenz and Engelmann, Michael and Schauer, Thomas and Bleicher, Achim}, title = {Experimental identification and verification of a moveable facade element for energy harvesting and vibration control}, series = {Journal of Building Engineering}, volume = {65}, journal = {Journal of Building Engineering}, issn = {2352-7102}, doi = {10.1016/j.jobe.2022.105712}, abstract = {The distributed-Multiple Tuned Facade Damping (d-MTFD) system was proposed to effectively reduce wind-induced vibrations of high-rise buildings by using the parallel moveable outer skin of the Double-Skin Facade (DSF) as damping mass. A full-scale prototype with a moveable (kinetic) DSF element has been built for first experimental tests using Hardware-in-the-Loop (HiL) simulations. The parallel moveability of the DSF's outer skin is achieved by mounting it on a smooth-running guide rail system. A stepper motor is applied as an adjustable electrical damper and simultaneously serves as an energy harvester. By using grey-box system identification, all the parameters of the prototype can be accurately estimated. For example, a low equivalent friction ratio of 0.0022 was estimated. The identified model achieved high fitness values (80\% to 91\%) compared to the measured data, providing the basis for the reliability of the experimental tests using HiL. The prototype is the hardware part of the HiL simulations, which is connected to the simulation part, namely, a 76-story, 306 m high benchmark building assumed to be installed with the d-MTFD system. The feasibility of using a stepper motor as an adjustable electrical damper for semi-active control has been successfully validated based on the HiL simulations. By using semi-active control, the relative displacement of the DSF's outer skin can be significantly reduced by about 35\% compared with using passive control. Energy harvesting performance has also been investigated. The average energy harvesting efficiency of the power electronics was experimentally determined as approximately 75\%. With consideration of all the parasitic damping in the connection, the average energy harvesting efficiency was about 50\%. For tests under across-wind excitation with a return period of 10 years, the self-sufficient operation of the semi-active d-MTFD system was proven to be achievable based on the prototype results. The average harvested power of the whole benchmark building (with 1000 moveable facade elements) can be predicted as 1.3 kW.}, language = {en} } @misc{ZhangWernickeWulffetal., author = {Zhang, Yangwen and Wernicke, Laurenz and Wulff, Wulf and Bleicher, Achim and Schauer, Thomas}, title = {Design and validation of a dual-functional damper based on a stepper motor for energy harvesting and vibration control}, series = {Mechanical Systems and Signal Processing}, volume = {200}, journal = {Mechanical Systems and Signal Processing}, number = {110568}, issn = {0888-3270}, doi = {10.1016/j.ymssp.2023.110568}, pages = {1 -- 19}, abstract = {Dampers are widely used to reduce undesired vibrations. In recent decades, they have been developed from the energy dissipation strategy to the energy harvesting strategy. Dual-functional dampers, which convert part of vibration energy into electrical energy, are intensively studied. DC motors are the most applied electromagnetic transducers in these studies. In this paper, two-phase stepper motors are applied as adjustable electrical dampers and energy harvesters. Dual-functional dampers using stepper motors inherently have higher damping density than those using DC motors, as stepper motors have more pole pairs than DC motors. The nonlinear theoretical electrical damping coefficient of two-phase stepper motors is derived and compared with that of DC motors. A dual two-stage Energy Harvesting Circuit (EHC) is proposed to realize the function of adjustable electrical damping through resistance emulation and the function of harvesting energy. A test bench is built to experimentally verify the adjustable electrical damping and energy harvesting performance of a selected two-phase hybrid stepper motor with the proposed dual two-stage energy harvesting circuit. The numerical solution from the identified model shows a high agreement with the experimental results. The energy harvesting efficiency in the electrical domain has reached about 85\%. This tested dual-functional damper using a stepper motor has been successfully integrated into a full-scale demonstrator of the distributed-Multiple Tuned Facade Damping (d-MTFD) system.}, language = {en} } @misc{JirasekSchauerSuetal., author = {Jirasek, Robert and Schauer, Thomas and Su, Di and Nagayama, Tomonori and Bleicher, Achim}, title = {Experimental linear parameter-varying model identification of an elastic kinetic roof structure}, series = {Engineering Structures}, volume = {297}, journal = {Engineering Structures}, issn = {0141-0296}, doi = {10.1016/j.engstruct.2023.116986}, pages = {1 -- 13}, abstract = {Elastic kinetic structures are a recent approach to design transformable lightweight structures. Their transformation is based on elastic bending, exploiting the compliant material behavior of the structural members. This enables transformable structures with a stable transformation process. However, due to their lightweight and flexible design, elastic kinetic structures are highly sensitive to static and dynamic disturbances. Moreover, such transformable structures exhibit a transformation state dependent dynamic behavior, due to geometric nonlinearities. Nevertheless, most of current research focuses on the principles of elastic kinetic transformation than on effective disturbance mitigation. The latter is usually designed based on low-order control-oriented models. This paper describes a system identification methodology, suitable to identify low-order models for the transformation state dependent dynamics of elastic kinetic structures. The system identification is carried out using a local approach in the linear parameter-varying (LPV) framework. For the identification of local linear time-invariant (LTI) models, the system realization using the information matrix (SRIM) method is applied. The collection of local LTI models is internally balanced using a balancing transformation, in order to represent the locally estimated models with respect to a common state-space basis. Via linear interpolation, an LPV system in grid-based representation is derived. This methodology is experimentally validated with data from an active hybrid roof structure prototype.}, language = {en} } @misc{ZhangSchauerBleicher, author = {Zhang, Yangwen and Schauer, Thomas and Bleicher, Achim}, title = {Optimized passive/semi-active vibration control using distributed-multiple tuned facade damping system in tall buildings}, series = {Journal of Building Engineering}, volume = {52}, journal = {Journal of Building Engineering}, issn = {2352-7102}, doi = {10.1016/j.jobe.2022.104416}, pages = {104416}, abstract = {To reduce wind-induced vibrations, Tuned Mass Dampers (TMD) are widely used in high-rise buildings. However, traditional TMD system requires large additional damping mass and huge installation space at the top floors of the building. In this paper, a novel distributed-Multiple Tuned Facade Damping (d-MTFD) system is investigated. This system employs the outer skin mass of the Double-Skin Facade (DSF) as the damping mass. In the upper stories, the DSF's outer skin, mounted on a guide rail system, is designed to be parallel moveable. The passive/semi-active d-MTFD system, which is assumed to be installed on a 76-story benchmark building under across-wind excitation, is optimized using multi-objective Genetic Algorithms (GA) for two defined objectives: minimizing the peak top floor acceleration and controlling the maximum peak relative displacement of all the moveable DSF's outer skins. On-off groundhook control and displacement-reducing bang-bang control are used as semi-active control strategies. The rolling friction caused by the guide rail system has a considerable impact on the optimization results. These results are presented in the form of Pareto fronts. Optimized parameters can be selected to yield a good trade-off between both objectives. The optimized passive/semi-active d-MTFD systems can highly improve the structural response. Compared with the optimized passive d-MTFD system, the use of semi-active control can reduce the vibration of the DSF's outer skin significantly. Comparing the selected optimized cases with similar peak top floor acceleration, the peak top floor facade relative displacement using displacement-reducing bang-bang control decreases 58.3\%, and the Root Mean Square (RMS) value decreases 61.4\%.}, language = {en} }