STRUCTURAL DAMAGE IDENTIFICATION BASED ON AR MODEL COEFFICIENTS AND COINTEGRATION FOR OFFSHORE PLATFORM UNDER ENVIRONMENTAL VARIATIONS

Changes of damage feature caused by structural damage are often masked by the changes caused by environmental variations (temperature, mass), resulting in the failure of vibration based damage identification methods. In this paper, the coefficients of AR model in time series and cointegration in econometrics are used to identify the damage of offshore platform in changing environmental variations (temperature, mass). Firstly, the AR model is used to fit the structural acceleration response from different nodes of the offshore platform pre and post damage, and the first-order AR coefficient is selected as cointegration variable. Secondly, the cointegration procedure is applied to the variables from different nodes and the cointegration residuals are taken as the damage indicators. Finally, the X-bar control chart is employed to identify the damage of structure. The results of numerical simulation and shaking table model test of a five-floor steel offshore platform verify the effectiveness of the proposed method.