FG Hybride Konstruktionen - Massivbau
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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.
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.
Experimental linear parameter-varying model identification of an elastic kinetic roof structure
(2023)
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.
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.
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%.
In structural engineering, active structures that combine the principles of lightweight construction with bending elastic component behavior are increasingly being investigated. For the realization of a prototype of an active hybrid roof structure at the laboratory of Hybrid Structures at BTU Cottbus-Senftenberg, preliminary investigations on a case study are conducted in the framework of this publication in order to improve the design process of these types of structures. These active hybrids require a higher design effort than classical structures from the field of structural engineering due to a larger number of relevant objectives. Consequently, this study devotes special attention to these essential target criteria and their mathematical formulation. Furthermore, in order to improve the efficiency of this design process, a hierarchical method is derived that is subdivided into two successive partial procedures, which contain specific heuristics that are developed. In this method, after structural optimization, an optimal actuator placement is performed. The subject of a design process involving optimal actuator placement is relatively unexplored for active structures in which components are subjected to large elastic bending deformations and is therefore the focus of this study. In order to verify the functionality of the method and the plausibility of the results of the derived partial methods, a validation of the methodology is performed. Therefore, results of analyses of an active truss structure are compared with those of an active hybrid structure, both derived using the presented method. In addition to validating results, the study intends to investigate whether the performance of an active hybrid structure generated by the proposed method is sufficiently competitive compared to a state-of-the-art active truss structure derived by the same procedure.
Elastic kinetic structures are a recent approach to design transformable structures. Their transformation is based on elastic bending, that is compliant component behavior of structural members. This principle can be used to realize transformable structures with a stable deployment process. Regardless of a stable transformation, elastic kinetic structures are prone to static and dynamic loads due to their lightweight design. However, most of current research on these structures solely focuses on the principles of transformation. This paper proposes a concept for an active hybrid roof structure with a transformation based on elastic kinetics and rigid-body motion. The concept exhibits a stable structural deployment and active control components to counteract static and dynamic disturbances. Furthermore, this paper includes the realization and experimental evaluation of a mid-scale prototype structure.
Die angestrebten Ziele einer Ressourcen- und Klimaneutralität erfordern ein radikaleres Umdenken der Bauschaffenden, das mit einer noch viel stärkeren Sensibilisierung der Auftraggeber für die Auswirkungen des Material- und Energieverbrauchs im Bausektor verbunden ist. Ein Ansatz, um diese Ziele zu erreichen, sind hybride Konstruktionen, in denen unterschiedliche Materialien, Elemente, Funktionen und Technologien auf mehreren Konstruktionsebenen ressourcen- und energieeffizient kombiniert sowie im Fall eines Rückbaus sortenrein rezykliert werden. Dieser anspruchsvolle Ansatz ist von Beginn an erklärtes Ziel des Lehrstuhls Hybride Konstruktionen – Massivbau an der BTU Cottbus-Senftenberg und zieht sich durch alle Lehr- und Forschungsaktivitäten. Mit ausgewählten Forschungsprojekten werden Motivation und Methoden hybrider Konstruktionen sowie deren Potenzial für ressourcen- und klimaneutrale Konstruktionen anhand von Prototypen aufgezeigt. Hierbei steht neben der ökologischen Weiterentwicklung klassischer hybrider Konstruktionen aus nachwachsenden und rezyklierten Rohstoffen, bspw. Holz und Recyclingbeton, auch die Entwicklung aktiver hybrider Konstruktionen im Fokus. Die gezielte Integration von aktiven Technologien wie Sensorik, Aktuatorik und Regelungstechnik ermöglicht multifunktionale Konstruktionen, einen hohen Nutzungskomfort, einen geringeren Rohstoffverbrauch bis hin zur Energiegewinnung aus dynamischen Einwirkungen.
Active Vibration Control of a Convertible Structure Based on a Polytopic LPV Model Representation
(2020)
This paper deals with modeling and control of lightweight convertible structures for the application in civil and structural engineering. Such structures are prone to vibrations due to their lightweight design. In addition, they exhibit transformation state dependent dynamic behavior. In order to guarantee a reliable operation, the use of active vibration control (AVC) is an effective means. For the example of a simplified convertible structure, modeling is demonstrated using the linear parameter-varying (LPV) framework. Based on local linear time-invariant (LTI) models, derived from a finite element model of the convertible structure, a polytopic LPV model is established. This LPV model is then utilized to design a polytopic LPV output-feedback controller for AVC during the structure’s transformation. The effectiveness of the designed controller is validated in simulation.
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.