| || Seismic applications of energy dampers
Author : Sinha, Shambhu
Source : Defence Science Journal ; Vol:54(1) ; 2004 ; pp 73-83
Subject : 624 Civil Engineering
Keywords : Dampers;Floor displacement;Relative displacement;Hysteretic;Forced deformation;Energy dissipation;Shock;Vibration;Viscous dampers;Energy dissipating fluid;Seismic loads;Fluid dampers
Abstract : Damping devices based on the operating principle of high velocity fluid flow through orifices have found numerous applications in the shock and vibration isolation of aerospace and defence systems. The study aims to investigate the feasibility of using energy dissipating fluid viscous dampers in structures to protect against seismic loads and to prove analytically and experimentally that fluid viscous dampers can improve the seismic capacity of a structure by reducing damage and displacement without increasing stresses. Both steel and concrete structures were considered. Extensive analytical and experimental investigations have led to the hazard mitigation applications on buildings bridges. A series of experiments were performed to demonstrate the benefits of fluid viscous damping devices in steel moment frame and reinforced concrete building models and a steel bridge model were tested, and all exhibited improved resistance to a variety of seismic loads. Furthermore, fluid dampers would be used as elements of seismic isolation systems for enhancing their energy dissipation capability.
| || Optimisation of an Active Suspension Force Controller using Genetic Algorithm for Random Input
Author : Hada, M. K.;Menon, A.;Bhave, S. Y.
Source : Defence Science Journal ; Vol:57(5) ; 2007 ; pp 691-706
Subject : 623.4 Armaments and Ballistics;620.261 Explosives
Keywords : Dampers;Genetic algorithm;Force cancellation control scheme;Active suspension
Abstract : A novel control scheme for the active suspension in a 4-DOFs half-car model is presented. A force cancellation control scheme is used to isolate the sprung and the unsprung masses. Skyhook damper and virtual damper concepts are employed to stabilise the sprung and unsprung masses respectively. Road-following springs are applied for the sprung mass to follow the trend of the road surface condition and to maintain the suspension stroke within a reasonable range. For efficiency, genetic algorithm is employed to search for the parameters like damping ratio and spring constant to achieve an optimum trade off among ride comfort, handling quality, and suspension stroke simultaneously for random input. Computer simulations are performed using MATLAB software to verify the proposed control scheme and effectiveness of the applied genetic algorithm.
| || Vibration isolation and transmissibility characteristics of passive sequential damper
Author : Patil, M. S.;Hada , M. K.;Bhave, S. Y.;Joshi, S. G.
Source : Defence Science Journal ; Vol:54(1) ; 2004 ; pp 39-51
Subject : 53 Applied Physics
Keywords : Dampers;Damping;Damping force;Passive vibration isolator;Vehicle isolator;Passive sequential damper ;Semi active vehicle suspension;Tunable damper;Fixed damping;Hydraulic damper;Damper control scheme
Abstract : This paper presents a half-car model (4-degrees-of-freedom) employing nonlinear passive sequential damper. The vibration isolation and transmissibility effect on the vehicle's centre of gravity (C.G.) has been studied. The results have been compared for transmissibility, displacement, and velocity transient response for half-car model having nonlinear passive sequential hydropneumatic damper under different terrain excitation.