Abstract
This paper proposes a pulse-echo Ultrasonic Testing (UT) methodology to quantify the damage of hysteretic dampers subjected to cyclic loadings. Energy dissipation is known as an innovative strategy for the protection of buildings against earthquakes. It consists of installing special devices called dampers in the construction, which are entrusted to dissipate most of the energy input by the earthquake, thus keeping the main structure basically undamaged. In particular, the hysteretic dampers dissipate the input energy through plastic deformations in their metallic parts. Several moderate ground motions would not exhaust the capacity of the dampers, but they cause damage—plastic deformations in the device. Therefore, continuous or periodic inspections of the damper are required in order to decide upon its eventual replacement. In this particular work, several hysteretic dampers made of stainless steel were subjected to different patterns of low-frequency cyclic loads that caused diverse levels of damage. Each damper underwent pulse-echo UT before and after the cyclic loading. Spectral energy of the echo signals was properly calculated at each damage level in order to define a reliable damage index. The new index has been compared with a well-established mechanical damage index, ID, previously proposed by the authors. A successful correlation was observed, making the pulse-echo UT technique promising for this particular application.
Highlights
The energy dissipation strategy for the passive protection of buildings and infrastructures against earthquakes has been growing during recent decades
The so-called hysteretic dampers or metallic dampers are based on the plastic deformation of metals as the source of the energy dissipation
Past research has proven that the level of damage and the failure of steel elements subjected to plastic deformations caused by arbitrarily applied cyclic loading can be reliably estimated by decomposing the force-displacement curves endured by the element into the so-called skeleton part and Bauschinger part [1]
Summary
The energy dissipation strategy for the passive protection of buildings and infrastructures against earthquakes has been growing during recent decades. Past research has proven that the level of damage and the failure of steel elements subjected to plastic deformations caused by arbitrarily applied cyclic loading can be reliably estimated by decomposing the force-displacement curves endured by the element into the so-called skeleton part and Bauschinger part [1] This decomposition is the basis of a phenomenological mechanical damage index called ID that has been extensively validated with static and dynamic tests. The new UT index can be reliably used to evaluate the level of damage on “slit plate” dampers with no need to know the load-displacement relationship endured by the damper
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