T-FVD (TIS Fluid Viscous Dampers) viscous damper is a velocity dependent energy dissipating device used in structural engineering  Its primary purpose is to dissipate the earthquake energy transmitted to the structure by converting it into heat energy through the movement of a piston passing through a viscous fluid.  T-FVDs can increase structural damping, typically between 15% and 35% in seismic applications, which significantly reduces drifts and stresses in a structure.