Mechanochromic Materials and Vision-Based Monitoring for Prestressed Concrete Bridges: A Full-Scale Benchmark Perspective

Prestressed concrete bridges are efficient and durable structural systems, but early-stage deterioration, prestress losses and localized stiffness reductions can remain weakly visible in the global dynamic response under service conditions. This paper develops a first framework for using mechanochromic materials as a visual sensing layer for Structural Health Monitoring (SHM) of bridge components. The approach starts from a full-scale benchmark bridge composed of three prestressed concrete girders and a cast-in-place slab, previously monitored through accelerometers, strain gauges, load cells, inclinometers and environmental sensors. Experimental measurements and nonlinear finite element simulations are used to identify critical regions where tensile stress redistribution and crack initiation are more likely to occur. These regions are proposed as target areas for mechanochromic coatings, whose color response can be acquired through fixed cameras or drone-based inspection. Images are transformed into calibrated RGB descriptors, tracked in time over selected regions of interest, and related to local strain through laboratory and in-situ calibration functions. The resulting strategy combines global SHM, physics-based modelling and localized vision-based sensing, providing a scalable route toward passive and interpretable monitoring of prestressed concrete bridges.