Multiphysics Modeling, Experimental Validation and Implementation of Viscous Dampers

Abstract eng:
The scope of this article is the design, testing, implementation and health-monitoring of viscous fluid dampers in a real building. First, a numerical model that captures the complex fluid dynamics and thermal behavior of the flow inside the damper is presented. Since these two phenomena are coupled, a multiphysics model was developed. The model was able to predict the force-velocity relationship, the pressure increase due to thermal expansion of the fluid, and the force decline as the fluid viscosity decreases, which are key aspects for satisfactory and efficient damper design. Using this model, the design of 78 units for a two tower 19-story building complex was accomplished. The devices, with a nominal capacity of 1275 kN, were developed in Chile and one unit, identical to the others, was shipped to the ATLSS Engineering Research Center at Lehigh University to undergo extensive testing in order to ensure the damper´s adequate performance and, at the same time, validate the numerical models used. Included among the many tests were: (i) harmonic cycles at maximum design velocity (362 mm/s); (ii) seismic input; and (iii) life cycle tests. In particular, the seismic movement displacement signal was obtained from a response-history analysis of a FE building model, subjected to an earthquake acceleration record compatible with the Peruvian seismic code. The displacement history of the most demanded device was used as input for the dynamic actuator at the Lab. Experimental results turned out to be in excellent agreement with numerical results in terms of output force, pressure increase, and viscosity decrease. Furthermore, damper performance was optimal, satisfying the energy dissipation demand and producing a force output with small deviation from nominal values. Finally, two of the 78 devices installed in the building were connected to a health-monitoring system including displacement sensors, accelerometers, internal pressure transducers, and temperature sensors. These were wired to a data acquisition system which can be monitored remotely online. The objective is to record damper displacement and output force during a future seismic event, which will provide valuable information on the real damper and building performance.

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