Ultrasonic testing and magnetic memory method for inspection of damage in hysteretic dampers subjected to cyclic loading

Abstract

Ultrasonic Testing (UT) and Metal Magnetic Memory (MMM) are proposed to quantify damage of hysteretic dampers (also known as metallic dampers) used as passive seismic control of building structures. Hysteretic dampers are special devices that are installed in a structure to dissipate most of the energy input by an earthquake through plastic deformations. Minor or moderate earthquakes do not exhaust the energy dissipation capacity of the dampers, though they cause damage. High-cycle fatigue problems can also arise when the damper is subjected to a large number of cycles of deformation in the elastic due to frequent loads such as wind. For these reasons, continuous or periodic inspection of the dampers is required in order to decide if they need to be replaced. Paper focus on a particular type of hysteretic damper that consists of plates made of stainless steel. These plates are intended to be used in conjunction with shape memory allows to develop a new brace-type damper with recentering properties. Both inspection methods have been validated on dampers subjected to quasi-static (low-frequency) cycling tests of increasing amplitude by means a high capacity actuator. Results showed a successful correlation with a well-established mechanical energy-based damage index based on the amount of accumulated plastic deformation and energy dissipation. © 2017 Slovenian Society for Non-Destructive Testing. All rights reserved.