Health monitoring of web plastifying dampers subjected to cyclic loading through vibration tests

Abstract

This article investigates experimentally the application of health monitoring techniques to assess the damage on a particular kind of hysteretic (metallic) damper called web plastifying dampers, which are subjected to cyclic loading. In general terms, hysteretic dampers are increasingly used as passive control systems in advanced earthquake-resistant structures. Nonparametric statistical processing of the signals obtained from simple vibration tests of the web plastifying damper is used here to propose an area index damage. This area index damage is compared with an alternative energy-based index of damage proposed in past research that is based on the decomposition of the load-displacement curve experienced by the damper. Index of damage has been proven to accurately predict the level of damage and the proximity to failure of web plastifying damper, but obtaining the load-displacement curve for its direct calculation requires the use of costly instrumentation. For this reason, the aim of this study is to estimate index of damage indirectly from simple vibration tests, calling for much simpler and cheaper instrumentation, through an auxiliary index called area index damage. Web plastifying damper is a particular type of hysteretic damper that uses the out-of-plane plastic deformation of the web of l-section steel segments as a source of energy dissipation. Four l-section steel segments with similar geometry were subjected to the same pattern of cyclic loading, and the damage was evaluated with the index of damage and area index damage indexes at several stages of the loading process. A good correlation was found between area index damage and index of damage. Based on this correlation, simple formulae are proposed to estimate index of damage from the area index damage.

Entropy Analysis for Damage Quantification of Hysteretic Dampers Used as Seismic Protection of Buildings

“…Given the wavelet energy, the WE and the damage index RWEE were calculated as explained in Section 4. In order to establish the reliability of the proposed index, a comparison with the mechanical damage index ID was carried out [3,4]. Firstly, a comparison was made for each repetition of the vibration test (T1, T2, T3, T4) at each level of damage of the I-section steel segments of specimen FD, and for T1, T2 and T3 of the I-section steel segment of specimen SD.…”

“…Given the wavelet energy, the WE and the damage index RWEE were calculated as explained in Section 4. In order to establish the reliability of the proposed index, a comparison with the mechanical damage index ID was carried out [3,4]. Given the wavelet energy, the WE and the damage index RWEE were calculated as explained in Section 4.…”

Wavelet energy ratio index for health monitoring of hysteretic dampers

“…It is well known that traditional Fourier‐based methods have been used for this purpose over several decades. In particular, for damage evaluation of WPD dampers, as reported in this paper, the authors have previously proposed and validated the use of the area damage index, based on the evaluation of changes in the frequency response function (FRF) calculated by means of the Fourier analysis . This paper demonstrates that the change induced by the damage is more clearly observable on the damage vector used to calculate the new index WER than on the FRF magnitude.…”

“…An alternative is to use piezoceramic sensors permanently attached to the hysteretic damper and conduct simple vibration tests . Piezoceramic sensors are low‐cost devices that can both excite and measure the response of the structural element whose health is to be assessed.…”

Ultrasonic Pulse-Echo Signal Analysis for Damage Evaluation of Metallic Slit-Plate Hysteretic Dampers

“…Vibration tests have been widely used in the literature [2] to perform modal analysis and to relate the damage to relative variations of modal damping and natural frequencies. In the past, the authors investigated a NDT method consisting of vibration tests [3][4][5][6][7][8] conducted with piezoceramic sensors attached to the hysteretic damper. In this context, the present paper investigates the application of pulse-echo Ultrasonic Tests (UT) as an alternative to the vibration method, to quantitatively assess the level of damage in a "slit plate" damper.…”