Retrofitting methodology for seismic performance enhancement of a 3D truss tower with scissor-jack linear- and nonlinear- viscous fluid dampers (VFDs) subjected to four types of ground excitations (El Centro, Kobe, Northridge and Taft) with their PGA normalized to 0.2g is described. The developed iterative retrofitting methodology is used for effective distribution of the scissor-jack linear- and nonlinear- VFDs with different capacities and stroke lengths along the height of the tower for satisfying the prescribed constraints on roof displacement, inter-bay drifts and permissible stresses in the members with the available VFDs. This method uses analytical formulae for effective damping ratios for linear- and nonlinear-VFDs for arriving at damping coefficients in scissor-jack linear- and nonlinear- VFDs placed at different bays of the tower. The procedure involves the linear- and nonlinear- modal time history analyses of bare 3D truss tower and the tower with scissor-jack linear- and nonlinear- VFDs along the height of the tower.

Keywords: 3D Truss towers, Viscous fluid dampers, Passive energy dissipation devices, Linear- and nonlinear- damper distribution methodologies, Scissor-jack mechanisms, Seismic retrofit.