Earthquake shaking has resulted in severe damage of structures built in the past 40 years, despite being designed according to building codes valid at the time of construction. Seismic displacement has been identified as the cause, and over the past four decades many seismic and wind engineering design and retrofit strategies have been employed. One such strategy is the addition of fluid dampers to limit excessive displacements, but it is still unknown if fluid dampers will maintain their long-term integrity. A new paper in the Journal of Engineering Mechanics explores an alternative idea.
In the paper, the authors offer a physical-motivated framework for mechanical characterization of a proposed pressurized sand damper, one that will benefit from future testing on various configurations of pressurized sand dampers. Learn more about "Pressurized Sand Damper for Earthquake and Wind Engineering: Design, Testing, and Characterization" by Nicos Makris, M.ASCE; Xenofon Palios; Gholamreza Moghimi, S.M.ASCE; and Stathis Bousias, M.ASCE, by reading the abstract below, or reading the full paper in the ASCE Library.
Abstract
This paper presents the development, testing, and characterization of an innovative low-cost fail-safe sustainable energy-dissipation device in which the material surrounding the moving piston and enclosed within the damper housing is pressurized sand. The proposed sand damper does not suffer from the challenge of viscous heating and failure of its end seals, and it can be implemented in harsh environments with either high or low temperatures. Its symmetric force output is velocity-independent, and it can be continuously monitored and adjusted at will with standard commercially available strain gauges installed along the post-tensioned rods that exert the pressure on the sand. Component testing at various levels of pressure, stroke amplitude, and cycling frequency show that the proposed pressurized sand damper exhibits stable hysteretic cyclic behavior with increasing pinching at larger strokes. The paper examines the fidelity of an eight-parameter Bouc-Wen hysteretic model capable to model pinching and concludes that the proposed hysteretic model is able to capture the pronounced pinching of the hysteretic behavior at larger stroke amplitudes. Four of the eight parameters of the proposed hysteretic model can be determined a priori from physical arguments; therefore, only the remaining four parameters need to be determined from nonlinear regression analysis.
Read the full paper in the ASCE Library: https://doi.org/10.1061/(ASCE)EM.1943-7889.0001902
