State-of-art review on load identification and response reconstruction to realize digital twin of infrastructures

The digital twin (DT) technique for infrastructures has been developed and attracted a significant amount of attention since 2020. Nonetheless, the key technologies used for DT, including load identification (LID), response reconstruction (RRE), and damage detection, have a much longer history than DT itself. By employing these methods, cyber models are established and updated to represent the operational state of a real structure, and meanwhile, the monitored data at discrete locations can be expanded to the full-field of the structure to realize DT. In this work, the LID and RRE methods for civil infrastructures under quasi-static and dynamic loading actions are comprehensively reviewed. In LID, four types of formulations are derived, and four solutions are summarized to address the inherent ill-posed problems. In RRE, the model- and data-driven methods are reviewed with five levels of performance. Subsequently, several full-field sensing techniques are introduced. The pros, cons, and features of these methods are highlighted. The challenges and prospects in LID and RRE are summarized to outline the future trend for in-service infrastructure digitalization.