TORSIONAL BALANCE OF TWO-WAY ASYMMETRIC PLANS WITH OPTIMAL DISTRIBUTION OF VISCOUS DAMPERS

Abstract eng:
Lateral-torsional coupling in asymmetric-plan buildings results in an increase of lateral displacement in the end-points of the building plan and therefore the production of disorderly deformation demand in seismically resistant frames. The demand for deformation in resistant frames depends on the relative magnitude of the plan translation and rotation and also the correlation between these two signals. Therefore, great correlation of small rotations with lateral displacement may result in considerably different deformations in the resistant frames of the structure’s two-edges. With regard to the inability to eliminate the asymmetric state due to various reasons such as architectural issues, in this study an attempt has been made to use supplemental dampers to decrease the lateral-torsional correlation of the plan displacement. This can result in a nearly uniform demand of deformation in seismically resistant frames. On this basis, using the concept of “torsional balance”, the optimized distribution of viscous dampers is determined for the decrease of this correlation by moving the “Empirical Center of Balance” (ECB) to the geometrical center of the structure. Which results in an equal mean-square-values of displacement in the edges of the plan. One-way and two-way mass asymmetry has been considered for torsional stiff and flexible structures and the optimal layout of dampers has been determined using the particle swarm optimization algorithm. The results show that the optimum center of viscous dampers depends on size of the mass eccentricity, uncoupled torsional-to-lateral frequency ratio and the amount of supplemental damping considered.

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