1. Design and Testing of a Gap Damper Device to Mitigate Rare Earthquake Pounding Response in Base-Isolated Buildings
- Author
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Rawlinson, Taylor, Marshall, Justin, Ryan, Keri, and Zargar, Hamed
- Abstract
Prior research has demonstrated the effectiveness of providing a delayed activation of supplemental energy dissipation in base-isolated structures. Providing the passive supplemental energy dissipation at a specified gap equal to or greater than the design displacement allows the base isolation system to act traditionally in design level events while activating the secondary system in extreme events. Use of this “gap damper” device eliminates undesirable effects often seen with supplemental damping at lower intensity motions and provides extra energy dissipation in extreme events to mitigate pounding. Using results from an analytical study, the primary purpose of this research is to develop two prototypes for practical implementation; one utilizing viscous damping and another utilizing viscous damping in parallel with a friction device. Development of the prototype demanded simplicity, feasibility, economy, and reliability to be an effective option in building design and construction. Important factors in the development of the device included bi-directional behavior, maximizing energy dissipation, contact stresses during the activation of the supplemental devices, and scalability. Multiple designs were proposed and a final design was chosen based on selection criteria and finite element analyses. The final design involves a protruding tube element extending downward from the base-isolated slab but not extending all the way to the basement floor. On the basement floor, a bumper system is attached to the supplemental energy dissipation devices. At a specified distance or “gap”, the protruding tube contacts the bumper system during an extreme event and activates the secondary energy dissipation. The two prototypes were designed and tested at Auburn University’s Structural Research Lab. Various load cases were implemented, simulating different velocities at the activation of the gap damper device. In addition, eccentric and oblique impacts were introduced to capture the bi-directional equilibrium capabilities of the system. Results of the experiment were compared to the theoretical models developed to verify performance. The multi-phase and bi-directional aspects of the system were captured in the results and analyzed to further understand the behavior of the system under different loading conditions. The results of the testing at Auburn shows that the device is performing as expected even when imperfections in the test-setup, both accidental and purposeful, are present. Working together with researchers at the University of Nevada-Reno, minor adjustments were made in the design and useful feedback was provided for the scaled shake table experiment to be performed at the UNR NEES facility. The test at UNR will consist of a one-quarter scale, three-story base-isolated frame specimen with a braced frame in one direction and a moment frame in the other direction. The shaking table test at UNR will provide a more inclusive and rigorous test of the device in two directions and will show the effect of the supplement energy activation on superstructure displacements and accelerations.
- Published
- 2014
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