Vibration Control of Adjacent Buildings Connected With Selected Types of Dampers

The optimality criterion is obtained with the help of root mean square value of inter-storey drift A study is also conducted to investigate the optimum exponential coefficient of the viscous dampers and optimum gain multiplier of the SAVFD and importance of those parameters in the structural–response reduction of adjacent buildings. Results show that using viscous and SAVFD to connect the adjacent dynamically similar structures can effectively reduce earthquake-induced responses of either structure but when SAVFD is used to connect soft and stiff buildings and results shows that SAVFD can control only displacements of both structures and it can’t control accelerations of soft structure. Further, lesser damper at appropriate locations can significantly reduce the earthquake response of the coupled system. The reduction in responses when two MDOF structures connected with 50% of the total dampers at appropriate locations is almost as much as when they are connected at all floors, thereby the cost of the dampers can be minimized. In the initial part of the study evaluate the application of viscous and semi active variable friction (SAVFD) damper for response control of seismically excited dynamically similar and dissimilar adjacent buildings. The numerical study is carried out in four parts, namely (a) two adjacent dynamically similar MDOF buildings connected by viscous dampers with optimum damping coefficient (b) two adjacent dynamically dissimilar MDOF buildings connected by viscous dampers with optimum damping coefficient (c) two adjacent dynamically similar MDOF buildings connected by SAVFD with optimum gain multiplier. (d) Two adjacent dynamically dissimilar MDOF buildings connected by SAVFD with optimum gain multiplier. The study is conducted for the two innovative arrangements of the dampers Keywords— Optimum damper parameters; Seismic response; Similar and dissimilar adjacent buildings; Viscous damper;SAVFD INTRODUCTION Earthquakes are the Earth's natural means of releasing stress. When the Earth's plates move against each other, stress is put on the lithosphere. When this stress is great enough, the lithosphere breaks or shifts. When the break occurs, the stress is released as energy which moves through the Earth in the form of waves, which can be felt and called an earthquake. There are many different types of earthquakes: tectonic, volcanic, collapse and explosion. The type of earthquake depends on the region where it occurs and the geological make-up of that region. The most common are tectonic earthquake these occur when rocks in the earth's crust break due to geological forces created by movement of tectonic plates. Another type volcanic earthquake occurs in conjunction with volcanic activity. The objectives of this study are to evaluate the application of viscous and semi active variable friction (SAVFD) damper for response control of seismically excited dynamically similar and dissimilar adjacent buildings. The numerical study is carried out in four parts, namely (a) two adjacent dynamically similar MDOF buildings connected by viscous dampers (b) two adjacent dynamically dissimilar MDOF buildings connected by viscous dampers (c) two adjacent dynamically similar MDOF buildings connected by SAVFD. (d) Two adjacent dynamically dissimilar MDOF buildings connected by SAVFD. Both dampers effectiveness is investigated in terms of the reduction of structural responses (namely, displacements and accelerations) of the connected adjacent buildings. A. PERFORMANCE OF VISCOUS DAMPER CONNECTE TO ADJACENT MDOF BUILDINGS Structural vibration control, as an advanced technology in engineering, consists of implementing energy dissipating devices into structures to reduce excessive structural vibrations(due to dynamic loads), to prevent catastrophic structural failure and enhance human comfort because of natural disturbances like strong earthquakes. In early 1990s, considerable attention has been paid to research and development of structural control devices, and medium and high rise structures have begun implementing energy dissipation devices or control systems to reduce excessive structural vibrations. The ideal force out for a viscous damper is given by, (1.1) Where Cmd is coefficient of damper, xi2-xi1 is relative velocity between the ends of i th damper and ε is exponent having value between 0 and 1.The damper with ε =1 is called a LVD (Linear viscous damper). The damper with ε larger than 1 have not been seen often in practical applications. The damper with ε smaller than 1 is called a nonlinear viscous damper which is effective in minimizing high velocity shocks Vol. 3 Issue 6, June 2014 International Journal of Engineering Research & Technology (IJERT) IJ E R T IJ E R T ISSN: 2278-0181 www.ijert. org IJERTV3IS061529 1431 B. Equation Motion of Connected Structures Let two structures having n stories, the mass, damping coefficient and shear stiffness values for the i th storey are mi, ci, ki. The combined system will then be having a total number of degrees of freedom equal to 2n. The equations of motion for this system are expressed as (1.2) Where M, C and K are the mass, damping and stiffness matrices of the combined structural system.CD is the additional damping matrix due to the installation of the viscous dampers but we are not considering additional damping due to installation of dampers. X is the relative displacement vector with respect to the ground, I is a vector with all its elements to unity, and xg is the ground acceleration at the foundations of the structures. The details of each matrix are given as,