میراگرهای جرمی تنظیم شده (TMD) بهینه تحت تاثیر اندرکنش ساختار لرزه ای خاک
Abstract
1- Introduction
2- Structural and seismic dynamic context
3- Optimum TMD parameters and response reduction
4- Additional results on the control of the foundation movement
5- Conclusions
References
Abstract
Tuned Mass Damper (TMD) devices are widely adopted as a valid mechanical solution for the vibration mitigation of structural systems and buildings under dynamic excitation. In the specific challenging context of seismic engineering, TMDs may represent a convenient option for both aseismic structural design and seismic retrofitting. However, the expectable efficiency rate of TMDs in that context is still debated. Besides, potential Soil-Structure Interaction (SSI) effects may become crucial in the mechanical system, and should properly be taken into account for the optimum TMD design, in order to avoid possible de-tuning. This work contributes to this framework, by investigating the effectiveness of an optimum TMD in reducing the linear structural response to strong-motion earthquakes of a given set of Multi-Degree-Of-Freedom (MDOF) low- and high-rise shear-type frame structures, by embedding SSI within the dynamic and TMD optimisation model. The TMD is seismically tuned through a dedicated two-variable optimisation procedure, for each specific case (primary structure, seismic event and soil type), therefore providing the optimum device setting for each given context. Average primary structure response indices are specifically targeted to that purpose, while maximum ones are monitored. A quite considerable range of optimisation cases is considered (eighty instances), to outline rather general considerations and average trends on TMD optimisation and effectiveness within the seismic SSI framework, for both low- and high-rise buildings. Such an investigation shall provide useful guidelines for a comprehensive tuning of TMDs in mechanical systems and specifically in the presence of seismic SSI, to be consulted in view of real-case applications.
Framing on TMD tuning
The present work concerns a methodological optimisation approach of Tuned Mass Damper (TMD) devices towards vibration mitigation and control of structural mechanical systems under dynamic (seismic) excitation. Specifically, the reduction of the linear earthquake response of low- to high-rise frame buildings equipped with a seismic-tuned TMD added on top is sought, by accounting also for Soil-Structure Interaction (SSI) effects that may jeopardise the response of the whole mechanical system and spoil the TMD tuning. The optimum TMD setting is achieved through an original seismic tuning methodology [1], based on an optimisation process apt to provide the optimum TMD selection for a given structure-earthquake case, which is being developed within a wider research mainstream on TMD tuning [1–5]. The seismic tuning process here considers a complete and extensive analysis on TMD optimisation and performance in the presence of seismic SSI, by focusing on the controlled (average) response of the primary structure. Also, the present investigation is conceived in conjunction with companion work [6], where a separate refined Frequency Domain Decomposition modal dynamic identification approach is developed (see also [7–12]), within the same seismic context explicitly considering SSI effects. Indeed, structural identification and TMD tuning may eventually be coupled into a single calibration process [9], on structures with unknown mechanical properties. The need for seismic protection of buildings motivated, during the last decades, the research investigation on different vibration abatement and control devices. In this sense, TMDs appear to be as one of the most validated mechanical solutions for the reduction of unwanted or excessive structural vibrations, with many existing examples of application to high-rise buildings and different type of structures [13]. In this sense, the adoption of TMDs in the realm of earthquake engineering still constitutes a strategic and currently discussed research and engineering topic, with a wider relevance also in more general terms for different mechanical systems within the realm of structural dynamics. The optimum TMD setting may be conveniently achieved through available tuning formulas, which however are strictly valid only for related benchmark ideal excitations.