Vibration control of structures using adjustable slippage elements

A new method for passive control of structural vibrations is introduced and investigated. The method is based on providing nonlinearity to the stiffness of a structure by installing elements with adjustable slippage in the proper locations. An adjustable slippage element (ASE) is a mechanical link with a two-branch elastic force–displacement response. The slippage threshold, which is the transition point between the two branches, can be adjusted within a relatively broad range, and can thus control the shape of the force–displacement curve of the element. An ASE can be used to rearrange the elastic restoring forces in the structure protected, and can be used separately or in combination with other passive control systems such as conventional damping devices. A structure equipped with such elements may gain enhanced dynamic performance, because the ASE redistributes elastic and plastic deformations, decreases force transmissibility, and improves resonance escape properties. These effects are achieved by separating the characteristic displacement within the ASE device among four prestressed elastic springs. The relative deformation between these elastic springs is controlled by their designed stiffness and also by the level of prestressing. The latter also controls the value of the slippage threshold of the device. The present study investigates the behavior and effectiveness of the proposed elements by considering a single-degree-of-freedom (SDOF) system equipped with an ASE and subjected to harmonic loading and earthquake base excitation.