Loss
of energy dissipation capacity from the deadzone in linear
and nonlinear viscous damping devices
Mai
Tong1 and Thomas Liebner2
1. Multidisciplinary Center for Earthquake Engineering
Research, State University of New York at Buffalo, USA
2. Department of Mechanical Engineering, Pennsylvania State University
Abstract:
In a viscous damping
device under cyclic loading, after the piston reaches a peak stroke, the reserve
movement that follows may sometimes experience a short period of delayed or
significantly reduced device force output. A similar delay or reduced device
force output may also occur at the damper¡¯s initial stroke as it moves away from
its neutral position. This phenomenon is referred to as the effect of ¡°deadzone¡±.
The deadzone can cause a loss of energy dissipation capacity and less efficient
vibration control. It is prominent in small amplitude vibrations. Although there
are many potential causes of deadzone such as environmental factors,
construction, material aging, and manufacture quality, in this paper, its
general effect in linear and nonlinear viscous damping devices is analyzed.
Based on classical dynamics and damping theory, a simple model is developed to
capture the effect of deadzone in terms of the loss of energy dissipation
capacity. The model provides several methods to estimate the loss of energy
dissipation within the deadzone in linear and sublinear viscous fluid dampers.
An empirical equation of loss of energy dissipation capacity versus deadzone
size is formulated, and the equivalent reduction of effective damping in SDOF
systems has been obtained. A laboratory experimental evaluation is carried out
to verify the effect of deadzone and its numerical approximation. Based on the
analysis, a modification is suggested to the corresponding formulas in FEMA 356
for calculation of equivalent damping if a deadzone is to be considered.
Keywords:
viscous damping device; stroke;
deadzone; sublinear; viscous fluid dampers
