Investigation of New Proposed Model for Mass Damper with Geometrically Nonlinear Stiffness

Abstract

Many studies have been conducted showing that the mass damper improves the performance of structures against wind loads and seismic loads. This paper presents a model for passive tuned mass damper with softening stiffness; the Newton−Raphson method and state space were used to solve nonlinear equations of motion. To evaluate the performance of the proposed mass damper, an 11-storied steel structure subjected to the Northridge and Zarand earthquakes was evaluated. This structure was initially modelled and analysed without a damper and with the softening PTMD. Then the effect of varying angles of the mass damper was investigated; eventually the damper was converted into a non-linear semi-active tuned mass damper. To reduce the displacements of the damper, fuzzy control was used for the controller. The results show that the proposed mass damper with a 60-degree angle could reduce the displacement in the earthquakes of Northridge and Zarand by 48.8 and 36.2% on an average. The results of using different angles suggest that a 45-degree angle makes for the most favourable performance for the structure and mass damper. It points out that in the use of an isolator for the 11th floor, this floor has the potential for higher displacement than any other floor, but, in this article, using the controller and the proposed semi-active damper, it has been shown that this floor can also experience lower displacement.

Keywords

• nonlinear tuned mass damper
• semi-active tuned mass damper
• softening stiffness
• nonlinear analysis
• the newton−raphson method
• geometrically nonlinear behavior