Apparent-Weakening in Fixed Base Structures

The acceleration and base shear of structures during strong ground motion can be attenuated by achieving bilinear-elastic behavior without any permanent-displacement also referred as “apparent weakening”. The negative stiffness device (NSD), used in this study, exhibits nonlinear-elastic negative stiffness behavior; by adding NSD to the elastic structure the resulting structure-device assembly behaves like an elastic-bilinear structure. Peak acceleration and base shear experienced by the structures can be reduced by adding the negative stiffness device and the additional deformations caused due to the reduced stiffness can be contained by adding the viscous damper. In this experiment, shake-table studies on a three-story fixed-base structure (3SFS) are conducted to demonstrate the concept of “apparent weakening” in elastic structural systems. Two NSDs and a viscous damper are installed in the first story of 3SFS. To accentuate the advantages of incorporating NSD in structures, responses of three different systems: 3SFS; 3SFS with NSD; 3SFS with NSD and damper; are compared for a suite of ground motions.