A bridge-tailored multi-temporal DInSAR approach for remote exploration of deformation characteristics and mechanisms of complexly structured bridges

With the increasing operation time and environmental loads, a growing number of bridges are in poor conditions and suffer from continuous structural deformation. In order to understand how those deformations occurred and developed, the knowledge of bridge deformation characteristics and mechanisms is essential for users to manage and maintain bridges sustainably. The Differential Synthetic Aperture Radar Interferometry (DInSAR) technique is an effective tool to observe the bridge deformation and has achieved a few impressive results. Nevertheless, the previous studies often focused on bridges with simple structure and high coherence, avoiding the difficulties in identifying dense and accurate point-like targets (PTs) upon complexly structured bridges with more severe de-correlation effects. Moreover, the traditional two-dimensional (2D) deformation maps of complexly structured bridges are difficult for non-expert users to understand in multi-dimensional views, increasing the difficulty of deformation interpretation. Finally, simply analyzing all the PTs’ deformation velocities equivalently without considering the structural information is insufficient to explore the deformation characteristics and mechanisms of complexly structured bridges. Starting from these limitations, we proposed a bridge-tailored multi-temporal DInSAR approach, and for the first time, explored the deformation characteristics and mechanisms of the complexly structured arch bridge and cable-stayed bridge. The density and accuracy of detectable PTs on bridges are improved by implementing a structure coherence-driven PTs selection strategy. A simple and fast algorithm for 3D visualization of bridge results is accomplished through integrating orthorectified PTs’ measurements from multi-track SAR datasets. Based on the 3D products, the deformation characteristics of different types of bridges are investigated by identifying the damage sensitive points (DSPs) and revealing the global deformations, and the deformation mechanisms of different bridge components are explored by analyzing the different types of PTs classified based on the spatial-temporal semantics. It is derived that the deformation characteristics of bridges are associated with their structural and material characteristics, and the deformation mechanisms of their DSPs are similar. The subsidence of land surface and foundations control the deformation of the pier-DSPs which mainly reflect the trend deformation of bridges, whereas the temperature variation drives the deformation temporal evolution of the span-DSPs which represent the elastic deformation of bridges.