The State-of-the-Practice of Modern Structural Health Monitoring for Bridges: A Comprehensive Review

Since the National Bridge Inventory (NBI) was first conducted, structural health monitoring (SHM) of the United States bridge infrastructure has consisted largely of labor-intensive, subjective measures like chain dragging and the tap test. Recent developments in a variety of sensor technologies and an improvement of computing and networking capabilities have allowed for the installation of in-situ sensor networks responsible for monitoring—among other parameters—the strain and deformation of structural members and concrete deck cracking. These relatively new techniques are quite costly, however, and in many cases are infeasible for SHM because they require installation in hard-to-reach places or during construction, limiting their application to the small number of bridges being built today compared to the current population of in-service bridges. Stand-off SHM techniques such as radar, electro-optical, laser scanning and other remote sensing technologies may offer an innovative, cost-effective method of monitoring the dynamic conditions of U.S. bridges in real-time. This paper investigates the state of the practice of SHM and provides summaries of existing technologies, both in-situ sensors and networks and remote techniques, as well as case studies of instrumented bridges.