Experimental & Analytical Investigation of Seismic Retrofit of Structures with Supplemental Damping: Part II - Friction Devices

The need for structures which function more reliably without damage during severe earthquakes was reemphasized by the behavior of structures during recent earthquakes (Lorna Prieta 1989, Northridge 1994, Kobe 1995, etc). The existing structures and often new ones must rely on large inelastic deformations in hysteretic behavior to dissipate the motion's energy, while the capacity to sustain such deformations is limited by previous non-ductile design or limitations of materials. An alternative method to reduce the demand of energy dissipation in the gravity load carrying elements of structures is the addition of damping devices. These devices dissipate most energy through heat transfer and reduce the deformation demands. In inelastic structures the supplemental damping mechanism reduces primarily deformations with small changes in the strength demand. The main benefit of added damping in the inelastic structures is the reduction of the demand for energy dissipation in the gravity load carrying structural members, thus reducing the deterioration of their low cycle fatigue capacity. An experimental investigation of different damping devices was carried out individually to allow for physical and mathematical modeling of their behavior. A series of shaking table tests of a 1:3 scale reinforced concrete frame incorporating these devices were performed after the frame was damaged by prior severe (simulated) earthquakes. Several different damping devices were used in this study: ( a) viscoelastic, (b) fluid viscous, ( c) friction (of two types) and (d) fluid viscous walls. An analytical platform for evaluation of structures integrating such devices was developed and incorporated in IDARe Version 3.2 ( Kunnath and Reinhorn, 1994). The experimental and analytical