Damage alarming analysis for ancient wood structures based on wavelet packet energy spectrum

Purpose – The purpose of this paper is to establish the damage alarming indexes for ancient wood structures and study the damage sensitivity and noise robustness of these indexes under random excitation. Design/methodology/approach – Xi’an Bell Tower is taken as a case in this paper to simulate the damage of ancient wood structures through finite element (FE) simulation and determine the satisfactory damage alarming indexes with wavelet packet energy spectrum. Findings – The results of this paper show that: 1) the damage alarming indexes can effectively identify the damage of ancient wood structures, each index with a different damage sensitivity; 2) the energy ratio deviation is greater than the energy ratio variance and is close to the maximum variation of energy ratio; 3) the energy ratio deviation has a better alarming effect than the energy ratio variance during the initial period of the damage. With the accumulation of the damage, the energy ratio variance outperforms the energy ratio deviation; 4) the sensitivity of the energy ratio deviation and variance varies from positions, changing from the highest to lowest at the mortise-and-tenon joints, the beam mid-span and the plinth; 5) if signal to noise ratio (SNR) is 40db or larger, the indexes can accurately identify the damage of ancient wood structures. As SNR increases, the indexes will have an increasingly higher sensitivity and certain ability to resist noise. Research limitations/implications – The FE model is simpiy, it does not completely reflect Xi’an Bell Tower. Practical implications – It will provide a theoretical basis for the damage alarming of Xi’an Bell Tower. Social implications – It makes structural health monitoring through structural vibration response under ambient excitation a new research field in damage detection as well as a positive way of ancient architecture protection. Originality/value – This paper studies the damage alarming effect on ancient wood structures from different wavelet functions and wavelet packet decomposition levels. To study the effect under white noise environment, this paper adds Gaussian white noise with a SNR of 10, 20, 30, 40 and 50 db to the acceleration response signal of intact structure and damaged structure.

Damage Location Identification of Truss Structure Based on Strain Modal Method

Due to the fatigue load and bad corrosion environment, truss structure in service will form the damage accumulation, damage detection of potentially damaged elements of truss structures is a challenging topic. According to the element stress characteristics of truss structure, structural element strain mode mainly based on the vibration displacement is derived, the change of elemental strain modal is proposed as the dynamic indicator for damage location identification of truss structure. Based on the numerical simulation study of the actual truss structure indicates that, the loworder elemental strain modal method is not only sensitive to damage identification of chord element and web element of truss structure, but also is effective to locate the damage of different position, and is suitable for damage alarming of truss structure in service.

A New Damage Alarm Index Based on Frequency Deviation for Structural Health Monitoring

Based on the statistics probability of certain order frequenciy deviates from its normal range, this paper puts forward a new damage alarm index and corresponding damage alarming method for structural health monitoring. Demonstrating the feasibility of this method, this article introduces the damage alarming method to analize the benchmark steel frame in frequency domain. The results show the abnormal index and its corresponding alarming method defined in sense of statistics indicates the abnormity of corresponding test cases clearly.

A Structural Damage Alarm Index Based on the Statistical Probability of Abnormal Frequency Offset

Based on the statistical probability of abnormal frequency offset, this paper puts forward a new structural damage alarm index. Demonstrating the feasibility of corresponding structural damage alarming method, this article introduces the index to analize a steel frame structure in frequency domain. The results show the abnormal index defined in sense of statistics indicates the abnormity of corresponding test cases clearly.

Application of Wavelet Packet Analysis in Damage Alarming for Steel-Frame Structure

The method of damage alarming based on wavelet packet analysis which applied on steel-frame structure is researched. Firstly, the method of damage identification based on wavelet packet analysis is introduced. Secondly, in view of the dependability of the method on the excitation, virtual impulse response function is brought in to enhance robustness of the method to the excitation. Lastly, through the steel-frame structure experimentation of damage alarming, the two damage modes of the structure are identified by the method based on wavelet packet energy spectrum. The experimentation results show that the effect of damage alarming to the steel-frame structure is completely obvious by wavelet packet analysis. Accordingly, this method has much application value for engineering.

Damage Alarming Method Based on Statistics to a Benchmark Structure

This paper addresses a new damage alarming method of structural health monitoring (SHM) which utilizes statistic method on information in frequency domain. The emphasis in this paper is on the application of this method to the benchmark structure by introduced an abnormal index. The results show this method could indicate the abnormity of corresponding test cases clearly.

Research on Damage Alarming Method of Structures Based on Information Statistics in Frequency Domain

This paper demonstrates the feasibility of a new structural damage alarming method based on statistics. The abnormal index was introduced to analyze the benchmark structure in frequency domain. The results show the abnormal index defined in sense of statistics indicates the abnormity of corresponding test cases clearly.