Completion of First Phase Testing of Negative Stiffness Concept. Live Public Viewing Aug. 30, 9AM EDT
NEESR-Adapt-Struct project http://www.ruf.rice.edu/~dsg/ NEESR-Adapt-Struct will be completing the first phase experimental “proof of concept” Negative Stiffness Device tests on Monday August 30, 2010 beginning 9 am EDT, with a short series of tests, streamed through the NEES network, starting at 9:00 am EDT. The tests to be broadcast in this first phase of the study will focus on the prototype of a negative stiffness device that was designed at University at Buffalo (UB), built by Taylor Devices, Inc., and tested by the researchers at UB and Rice University in a three stories structural model isolated with elastomeric bearings. By designing a ductile structure and letting the structure yield under strong earthquakes, the forces acting on the structure can be reduced to the level dictated by the yield level. However, the structure undergoes permanent displacement. In this study, yielding is emulated in a structural system by adding an "adaptive negative stiffness device" and shifting the “yielding” away from the main structural system—leading to the new idea of "apparent softening and weakening" that occurs ensuring structural stability at all displacement amplitudes. For this purpose a novel adaptive negative stiffness device, NSD, that is capable of changing the stiffness as a function of device displacement, is developed. In the presence of the negative stiffness devices, the model experiences lower accelerations and base shear, while the increased deformations are controlled and reduced by viscous-fluid supplemental dampers. First phase testing verified the concept and determined the influence and efficiency of the device, the imperfections in construction and placement of devices, and full characterization of the rigid body dynamics influencing the devices. Final experiments are currently underway. The functioning of the negative stiffness device will be visible in the live video broadcast from http://nees.buffalor.edu A. A. S. Sarlis (UB), D. T. R. Pasala (Rice U.) – PhD Students, PI: S. Nagarajaiah (Rice U), Co- PI’s: M. C. Constantinou (UB), A. M. Reinhorn (UB), D. Taylor (Taylor Devices, Inc), Michael Symans (RPI), Jian Zhang (UCLA), Thomas Attard (UTK).