Theoretical Analysis Of Inerter And Shape Memory Alloy（SMA） Based Passive Control Devices For Structural Vibration Mitigation

The current increasing trend towards the construction of high-rise structures with the use of lightweight,high strength materials and advanced engineering techniques has led to more flexible,slender and lightly damped structures.As a result,these structures become very sensitive to environmental excitations such as wind and earthquakes and may lead to severe vibrations inducing structural damage and occupant discomfort.Therefore,it is of utmost importance to develop practical and efficient strategies to protect these structures from unwanted vibrations.The most commonly used vibration suppression technique is installing passive control devices such as Tuned Mass Damper（TMD）,to reduce the mechanical vibrations in the host structure where the natural frequency of the damper mass is tuned to be similar to the resonant frequency of the structure they are mounted to.Liquid dampers（such as Tuned liquid damper（TLD）and Tuned liquid column damper（TLCD））are a special class of TMD where the damper mass is replaced by liquid such as water.TLCDs rely on the motion of a liquid column in a U-tube-shaped container to counteract the forces acting on the structure,where the damping is introduced through an orifice installed inside the container.The main motive of this dissertation is to study and develop the advanced version of conventional control devices（i.e.,TLCD and TMD）using smart devices such as inerter and shape memory alloy resulting into TLCDI and SMA-TMDI,for their application towards mitigation of structural responses under seismic excitations.An inerter is a twoterminal mechanical device which exploits its mass amplification effects and develops internal resisting forces proportional to the relative acceleration of its terminals.Two notable thermomechanical properties of SMA are the shape memory effect and superelasticity.SMAs possess super-elasticity property which enables SMA material to recover its original shape upon unloading with zero-residual strain.The first chapter（Chapter 1）of this dissertation introduces the current research work including background,literature review and motivation behind the study as well as the objectives which are obtained as a result of the present research study.The next two chapters（Chapter 2 and Chapter 3）,discuss the application of TLCDI and SMA-TMDI in controlling seismic vibrations of a SDOF structure and linked-SDOF structural systems respectively.The content in these two chapters are arranged as follows,（1）Firstly,the mathematical formulation of the TLCDI and SMA-TMDI controlled systems have been presented.（2）Thereafter,equivalent linearization method is used to solve non-linear motion equations.Based on the equivalent linearization method,the analytical expressions of the responses of the controlled systems have been derived and the parametric analysis of the controlled systems is performed under stationary excitation.（3）Multi-objective parametric optimization has been performed to derive the optimal parameters and the responses of the TLCDI and SMA-TMDI controlled systems subjected to stationary white-noise excitation.（4）The optimal performances of the proposed TLCDI and SMA-TMDI systems have been assessed under stationary white noise excitation as well as non-stationary excitations and recorded earthquakes.The performances of the TLCDI and SMA-TMDI systems were compared with those of the conventional TLCD and TMDI controlled systems,respectively.It was concluded that inerter-based TLCD and SMA-based TMDI showed improved performances as compared to classical TLCD and TMDI systems in terms of vibration mitigation of SDOF structure and linked-SDOF structures.