**Viscous damping acts 90****o**** out of phase
with structural bending. It fattens the ****hysteresis loop.
**
**
**

**Optimum values for C & n must be found. (n = .4
for San Bernardino Medical ****Center,
.75 for Golden Gate) and the best number of dampers and locations must ****also be found.
**
**
**

**The initial model should be fairly simple, and could
use modal analysis with ****dampers
represented as modal damping (n = l.0). We know that 20% to 30% works ****well. This initial model can determine the optimum
"n".
**
**
**

**A later model should be a finite element detailed
model with discrete damper ****elements. It should permit nonlinear damping
(“n" that is other than 1.0). This ****model will provide an estimate of the number and
location of dampers as well as ****their
force and velocity requirements. At
this stage a two dimensional model ****should be sufficient.
**
**
**

**Later, if the structure is torsional, it may be
necessary to proceed with a three ****dimensional finite element model.**
Analysis Considerations