Studies on fire-induced vibration of full-scale continuous panels using Hilbert transform

Abstract

Fire-induced vibration of four panels A-D has been studied and also relevant furnace temperature, temperature gradient, deflections and cracking distributions introduced. Time-domain analysis indicating vibration intensity has important relationships with boundary constraints. According to vibration intensity, the whole vibration process can be divided into three stages. During the first and third stages, acceleration signals are relatively low but during the second stage, vibration signals are strong so that more signal mutations have been detected. The signal mutations are due to the appearance of the main cracks. Frequency-domain analysis adopting Hilbert Transform (HT) shows that frequencies have been affected by cracks propagation and boundary constraints but the changes have not been influenced by damage locations in each panel. Furthermore, frequencies have fluctuated little in the first stage, but during the second stage, frequencies have fluctuated dramatically as a result of cracking propagations and an obvious falling trend has appeared. Also, in this stage frequencies have increased as a result of temporary swelling and increased friction within the panels. In the third stage, frequencies have changed smoothly and declined quickly.  Moreover, the three stages of frequency changes correspond to the three stages of deflection changes in sequence. Therefore, characteristics of fire behaviour including deformation and cracks of the panels can be monitored through analysis of vibration.