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.
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.
Facade-Integrated Semi-Active Vibration Control for Wind-Excited Super-Slender Tall Buildings
(2020)
Nowadays, skyscrapers are getting higher and more slender due to inner-city concentration, which makes the structure more susceptible to dynamic excitations. The design of super-slender skyscrapers is governed primarily by wind excitation. A traditional Tuned Mass Damper (TMD) has been installed in many skyscrapers to mitigate wind-induced vibrations, which has been proven to be very reliable. However, it needs large additional mass and huge installation space near the top of the building, which makes TMD not optimal for superslender skyscrapers. In this paper, a semi-active distributed-Multiple Tuned Facade Damper (d-MTFD) using movable facade elements as damping mass is investigated. The facade elements at the upper stories of the building are parallel movable to the primary structure. Electrical Machines (EM) as variable damper are integrated in their connections to realize semi-active vibration control, which makes the system more effective and robust. For real application, a practical design criterion is that the relative displacement of the facade elements cannot be too large, otherwise it makes the occupants feel uncomfortable. Therefore, multi-objective Genetic Algorithm (GA)-optimized on-off groundhook semi-active control is applied, where two control objectives are optimized. One control objective is to minimize the peak top floor acceleration and the other control objective is to minimize the maximum peak relative displacement of all the facade elements. As a result, a Pareto Front shows that better vibration suppression performance and smaller facade relative displacement can be achieved using the multi-objective optimized controller.
This paper presents a sustainable semi-active distributed-Multiple Tuned Facade Damping (d-MTFD) system that utilizes the existing mass of the Double-Skin Facade's outer skin as damping mass to mitigate structural vibrations caused by wind excitation. Based on this concept, a prototype with one full-scale parallel moveable facade element has been developed, built, and validated. A stepper motor working together with its connected energy harvesting circuit is innovatively applied as an adjustable electrical damper and simultaneously as an energy harvester. Its feasibility has been proven through experiments using Hardware-in-the-Loop (HiL) simulations. An energy harvesting efficiency of 75% was achieved by using a two-stage power converter as the energy harvesting circuit. The self-sufficiency of the semi-active d-MTFD system was achieved.
The worlds spectacular skylines host tall and slender buildings to create a maximum of office, residential and commercial space on a minimized footprint. These structures need to cope with increasing wind forces at height and are additionally affected by wind-induced vibration due to their lower natural frequencies. The resulting vibrations make users uncomfortable. Therefore, heavy tuned mass dampers are installed in structures and occupy valuable space especially in the costliest top-floors. As an example, Taipei 101’s steel damper is located between the 87th and 91st floor and weights astonishing 660 metric tons. This raises the need for additional reinforcement which increases cost and carbon footprint.Most buildings in expensive metropolises are cladded with remarkable glass facades. Therefore, we asked the question if it was possible to use the existing mass – more specifically the glass mass in a Double‑Skin Facade – to dampen the building’s movement, create a comfortable space for the user, exploit more floor area for the investor and finally to minimize the amount of building material to reduce carbon footprint for society. The idea was realized in a collaborative research effort of TU Berlin, BTU Cottbus-Senftenberg and Josef Gartner GmbH that resulted in a full-scale mock-up of a Double‑Skin Facade. Its outer skin can move laterally on a guide rail system. As the building starts to move, the facade's inner skin remains fixed to the base structure while the outer skin follows the building’s movement in a delayed manner due to its mass inertia. The fixed inner skin and the moveable outer skin are connected by a spring system that is tuned to the first natural frequency of the base structure. During the motion of the facade’s outer skin, the spring system redirects the relative movement and generates a stabilizing force for the base structure in the opposite direction. Additionally, an electrical machine is placed in between to provide an adjustable damping effect for semi-active and passive control. It also serves the purpose of a generator to study the opportunity to harvest energy. The paper shows the structural design options for the novel facade concept in the context of a project review of Double-Skin and Closed-Cavity Facades. The function of a full-scale mock-up, its fabrication and installation are described to show feasibility and ongoing challenges. First test results reveal a close match between theoretical assumptions and the applied testing. This engineering-driven and experimentally validated design opens a new field of architectural options in sustainable facade design which is focused on tuning physical parameters that affect the damping properties of the global structure.
Tall buildings are increasingly built worldwide due to significant economic benefits in dense urban land use. But super-slender tall buildings are very susceptible to wind excitation. Tuned Mass Damper (TMD) and distributed-Multiple Tuned Mass Damper (d-MTMD) have been widely investigated passively and actively and proven to be e cient solutions to mitigate the structure vibration. However, they both need additional mass and huge installation space near the top of the building. In this contribution, a new semi-active distributed-Multiple Tuned Façade Damper (d-MTFD) is investigated that employs the mass of the outer skin of a Double-Skin Façade (DSF) as damping mass. The outer skin of DSF at the upper storeys of the building are parallel moveable to the inner skin fixed on the primary structure. A design criterion besides the damping of the primary structure vibration is that the relative displacement of the outer skin with respect to the inner skin fixed on the primary structure should not be too large. Otherwise, it makes the occupants feel uncomfortable and imposes too high constructional demands. Therefore, on-o ground-hook control is investigated, where the two control objectives are optimized using genetic algorithms. One control objective is to minimize the peak top floor acceleration, and the other control objective is to reduce the maximum peak relative displacement of all the moveable outer skins. This multi-objective optimization results in a Pareto Front, which allows choosing controller settings that yield a good trade-o between both objectives. The approach has been first validated in a simulation with a 306 m benchmark building for a wind speed of 13,5 m/s at 10 m above ground level with a return period of 10 years. Acceptable peak top floor accelerations for hotel usage and a maximal displacement between the primary structure and the moveable outer skin less than ± 0.5 m could be achieved despite the presence of rolling friction. The variable damping coe cients for the on-o ground-hook control can be realized by means of a stepper motor in each moveable DSF element which acts as a generator using customized power electronics for energy harvesting. An open research question is if the harvested energy will be su cient for enabling a self-sustainable operation of the embedded control system and power electronics. Further validations will be carried out in Hardware-in-the-Loop (HiL) simulations in which a currently built prototype of one moveable DSF element will be physically connected to the simulation of the benchmark building.
Weltweit werden immer mehr „superschlanke“ Hochhäuser gebaut, da sie bei einer dichten städtischen Flächennutzung erhebliche wirtschaftliche Vorteile bieten. Jedoch sind sie sehr anfällig für Windanregungen. Schwingungstilger sind passiv als auch aktiv Stand der Technik und haben sich als effiziente Lösungen zur Dämpfung Wind-induzierter Strukturschwingungen erwiesen. Dieser Ansatz benötigt jedoch zusätzliche Masse und einen großen Bauraum in den begehrten obersten Etagen. In diesem Forschungsprojekt wurde ein neuer semiaktiver und verteilter Fassadendämpfer untersucht, der die Masse der Außenhaut einer Doppelfassade im Sinne der Ressourceneffizienz als Dämpfungsmasse nutzt.
Für die Realisierung einer zeitlich veränderlichen Dämpfung wurde ein mechatronischer Schwingungsdämpfer inklusive Energie-Harvester entwickelt, der Energie in einer Batterie speichert. Zur Validierung der Konzepte und zum Nachweis des autarken Betriebs des geregelten Dämpfungssystems wurde in Zusammenarbeit mit der Josef Gartner GmbH ein bewegliches Doppelfassadenelement als Prototyp realisiert und auf einem Versuchsstand installiert. Dies erlaubt die Durchführung von Hardware-in-the-Loop Simulationen, bei denen ein gesamtes Gebäude simuliert wird und ein einzelnes Fassadenelement als Hardware physisch aktiv ist und sein Verhalten untersucht werden kann. Die Machbarkeit einer autarken semiaktiven Dämpfung mit parallel beweglichen Prallscheiben an Doppelfassaden konnte somit erfolgreich demonstriert werden. Der Ansatz liefert einen Beitrag, den CO2-Fußabdruck eines Hochhauses zu reduzieren.