DEFORMATION MONITORING AND SENSITIVITY ANALYSIS OF UNDER-CONSTRUCTION BRIDGES CONSIDERING PS OPTIMIZATION

Abstract. During the construction and operation of bridges, safety accidents can occur due to improper design, construction, development of structural diseases, and inadequate maintenance measures. Such incidents can lead to significant property damage and casualties. InSAR technology is increasingly playing a critical role in the deformation monitoring of linear projects, such as bridges and roads because it is not affected by light and weather conditions. However, in the process of bridge construction, the instability of the environment often results in low scattering intensity, which can make it challenging to obtain a sufficient number of permanent scatterer (PS) points. This study proposes a method to optimize the identification of PS points by combining amplitude dispersion index, statistical median of amplitude mean, and temporal coherence coefficient, based on TerraSAR-X data. We then employed PS-InSAR technology to monitor the deformation of the under-construction bridge over the JingXiong Expressway-Yongding River, China. Furthermore, we conducted temporal subsidence analysis for different structural locations of the bridge while combining temperature data from weather stations to carry out a sensitivity analysis of the bridge deformation. The study results demonstrated that (1) the proposed method for optimizing the identification of PS points outperformed the two traditional methods in terms of increasing the selection of PS candidates by 14% and 10% respectively, while also leading to better quality identification of the PS candidates; (2) the main body of the under-construction bridge appeared relatively stable at present, with the deformation of the bored cast-in-situ piles and the connection of the approach span and abutment showing greater magnitude compared to other areas. Thus, it is essential to conduct regular monitoring of these regions and implement preventive measures in the future; and (3) the deformation of the under-construction bridge is correlated with the ambient temperature, and different structural locations display varying sensitivity to temperature changes. The findings of this study can help guide the subsequent construction and safe operation of the under-construction bridge after completion.