AN EQUIVALENT STATIC ANALYSIS PROCEDURE FOR STRUCTURES WITH ADDED VISCOUS DAMPERS

In the present paper the method of equivalent static forces (or lateral force method), widely used in earthquake engineering especially in the phase of preliminary design of regular framed structures, is extended to the case of structures equipped with added viscous dampers. The method is grounded on basic principles of structural dynamics and, under certain assumptions, allows to estimate the maximum damper forces and maximum internal actions in the structural members due to the design earthquake through analytical formulas only. In order to show its effectiveness, the method is finally applied for the retrofit through external steel “dissipative towers” (namely steel moment-resisting frames equipped with interstorey viscous dampers) of a 16-storey reinforced concrete building.