Effect of N-damped outriggers on high-rise structure subjected to earthquake loads

The effect of the placement of many damped outriggers attached on a high-rise structure is investigated in this paper. The equation governing the vibration proposed, is deduced from a Bernoulli-Euler beam where the geometrical nonlinearity is taken into account. An analytical solution is developed using Galerkin method and the damping function is given. The analysis shows that, outriggers behave differently on each of the firsts five modes of vibrations and the ideal position to locate an outrigger on a cantilever beam is near the top level only for the first mode of vibration. When the number of outriggers increases, the damping ratio of the system increases too and vibrations are reduced. For smallest values of located damper and the distance of location, the damping coefficient of the whole system is quite important due to outrigger damper while for highest values, the distance of location influence more the total damping coefficient. The position of the outrigger affects considerably the amplitude of vibration according to the considered mode.