ANALYTICAL MODELING OF A FRICTION DAMPER

Abstract

Conventional procedures of seismic refurbishment of structures which are not designed to withstand high seismic acceleration ground motion are very much difficult due to the fact that shear wall requires extra additional foundation work to be done and steel bracings are quite expensive and some modification with structural member is required. Addition of Passive damping devices to steel moment resisting frame changes the stress and strain which is borne by the structure from “Hardening phase” to “Severe Hardening phase”. Friction Damper is passive energy dissipating device that dissipates energy through the friction between the contacts of two solid surfaces. They are simple to manufacture and very easy to install at their appropriate place. They are very efficient energy dissipating devices with ease for maintenance. They can be used for many structures to reduce the seismic response of the structures. The use of friction dampers is becoming popular. There are many parameters for deciding the efficient use of friction dampers i.e. optimum slip load, material of construction, arrangement of different components etc. Therefore these parameters need to be addressed before the efficient use of friction device for the seismic protection of the structures. The discovery of Novel friction device one which has a horizontal plate and vertical plate invented by Imad H Mualla [2] in the year 2000 is one of the most developed friction damper devices which is being used in the world and lot of experiments are being carried out for the extraction of the characteristic exploitation of the device. The device can have single unit for a desired performance or multiunit for its performance as per the requirement of the seismic dissipation of the energy. Experiments conducted shows that Multiunit novel friction devices [2] are better dissipator of energy of structures which are located on high seismic risk areas. This type of dampers adds on the structural stiffness before attaining their slip load, but after sliding stiffness rate is equal to stiffness of a frame void of damper. The structures which are benefitted by increase of stiffness, the damper will improve their seismic behaviour. Non Linear time history Dynamic analysis has been put into use through seismo Struct software [14]. Numerical evaluation to find out the value of slip load can be done by the method as proposed by A.Filiatrault and S.Cherry [4]. Three storey building with specified dimensions are taken and loading arrangement is assumed as per [11], certain output parameters are obtained. iv The detailed calculation is shown in the subsequent portion. The most important parameter on which efficiency of the frictional damper depends is Optimum Slip Load. Evaluation of Optimum Slip Load is not an easy process, so equations are proposed by A.Filiatrault and S.Cherry [4]. Rapid evaluation of the above parameter can be made by the use of design slip load spectrum. Design slip load spectrum takes into account the properties of the structure and ground motion which is expected at the construction site. SAP2000 is used for design of three storied building; a comparison is studied between bare frame and frame equipped with Rotational friction damper.