A new approach in passive structural control by using adjustable slippage elements.

摘要

A new approach in passive structural control is introduced and investigated. It is based on the use of nonlinear elements with adjustable slippage.; The proposed method considers the “rearrangement”of the elastic restoring forces in conventional damping devices and other passive control systems. It allows the slippage threshold of a nonlinear connecting element (joint) to be adjusted within a relatively broad range. In fact, the force-displacement curve of such a nonlinear element can be manipulated and modeled in order to obtain a structure with enhanced dynamic performance based on redistribution of elastic and plastic deformations, decreased force transmissibility, and improved resonance escape properties. This is achieved by separating the characteristic relative displacement of the proposed devices into right and left (or positive and negative). The elastic elements (springs) providing the required stiffness for these separate relative displacements are prestressed and the level of prestressing determines (controls) the value of the slippage threshold.; A brief literature review of the contemporary design approaches and concepts for earthquake resistant structures is provided and the possibilities and variants for application of the proposed approach both to new and existing structures are examined.; The effectiveness of the proposed method is investigated by extensive numerical and Finite Element (FE) simulations of different structural systems.; A steady-state dynamic analysis of various damped and undamped nonlinear single degree of freedom (SDOF) systems with adjustable slippage elements is carried out. A parametric study is performed in order to estimate the influence of the factors controlling the shape of the force- displacement curve and the slippage threshold of the proposed elements. The influence of these factors and parameters on the effectiveness of the adjustable slippage elements is further investigated by applying ground acceleration excitation from a real earthquake event to the same SDOF systems. Pseudo-acceleration nonlinear response spectra for the considered earthquake are developed and compared for different force-displacement curves and various slippage thresholds.; The effectiveness of the proposed approach in passive structural control of multidegree-of-freedom (MDOF) systems is investigated considering a four-storey steel. frame with adjustable slippage elements with varying thresholds. Different structural response values, such as maximum floor accelerations and maximum floor displacements, are compared and an optimum combination of thresholds of the slippage elements is suggested with respect to minimizing selected structural response values, such as total base shear force and total base overturning moment.; Based on the results of the parametric studies, recommendations for implementation of the proposed control approach and adjustable slippage elements in the common earthquake engineering practice are provided.