Y.-B. Liang’s scientific contributions

Structure frequency, which is always regarded as damage detection feature for its more convenient testability and higher measurement precision, is also susceptible to environmental and operational variations. The variations lead to frequency sequence non-stationary and make much disturbances for actual structure health monitoring and damage detection. So cointegration method in econometrics is introduced to deal with the non-stationary problem by the linear combination of non-stationary variables, thus the non-stationary problem for structure damage detection feature caused by environmental factor variation is transformed to stationary problem. At first, ADF (augmented Dickey-Fuller) test and EG (Engle-Granger) test are detailedly introduced to check non-stationary order of the feature sequence and calculate the cointegration coefficients. Next, the cointegration relationship between frequency sequences is verified using a simple supported beam and online damage detection procedure based on cointegration of frequency under the influence of environmental temperature is introduced. At last, the validity and robustness of the proposed method are illustrated through a prestressed concrete beam and a simple supported steel bridge.