  Performance-based optimization of energy dissipation devices in structures
necessitates massive and repetitive dynamic analyses. In the endurance time
method known as a rather fast dynamic analysis procedure, structures are
subjected to intensifying dynamic excitations and their response at multiple
intensity levels is estimated by a minimal number of analyses. So, this method
significantly reduces computational endeavors. In this paper, the endurance
time method is employed to determine the optimal placement of viscous dampers
in a weak structure to achieve the desired performance at various hazard
levels, simultaneously. The viscous damper is one of the energy dissipation
systems which can dissipate a large amount of seismic input energy to the
structure. To this end, hysteretic energy compatible endurance time excitation
functions are used and the validity of the results is investigated by comparing
them with the results obtained from a suite of ground motions. To optimize the
placement of the dampers, the genetic algorithm is used. The damping
coefficients of the dampers are considered as design variables in the
optimization procedure and determined in such a way that the sum of them has a
minimum value. The behavior of the weak structure before and after
rehabilitation is also investigated using endurance time and nonlinear time
history analysis procedures in different hazard levels.
