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 stiffne ss of a structure by installing elements with adjustable slippage in the pr oper locations. An adjustable slippage element (ASE) is a mechanical link w ith a two-branch elastic force-displacement response. The slippage threshol d, 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 forc e-displacement curve of the element. An ASE can be used to rearrange the el astic restoring forces in the structure protected, and can be used separate ly or in combination with other passive control systems such as conventiona l damping devices. A structure equipped with such elements may gain enhance d dynamic performance, because the ASE redistributes elastic and plastic de formations, decreases force transmissibility, and improves resonance escape properties. These effects are achieved by separating the characteristic di splacement within the ASE device among four prestressed elastic springs. Th e 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 stu dy investigates the behavior and effectiveness of the proposed elements by considering a single-degree-of-freedom (SDOF) system equipped with an ASE a nd subjected to harmonic lending and earthquake base excitation. (C) 2000 E lsevier Science Ltd. All rights reserved.