Fracture Critical Member (FCB) is defined as component intension whose failure is expected to result in the collapse of the bridge/structure or the inability of the bridge/ structure to perform its function. A fracture-critical bridge or other structure has a structural component of which failure could lead to bridge distress and possibly collapse. The failure of a single major tension member or member element is likely to cause a significant portion or the entire bridge to collapse due to a lack of redundancy. Fracture critical designs can leave bridges vulnerable to possible collisions with ships or large trucks. A bridge/ structure can become fracture critical if deterioration over time leads to degradation of materials compared to their original design strengths, or if loading use increases such that designed redundancy is reduced.

Typical applications of fracture critical monitoring include steel bridges, long span concrete bridges, bearings, piers, girders, truss members, gusset plates, floor beams, stringers, parking garages, pedestrian walkways, rail road structure and bridges, foundation, power and utility or petrochemical support structures. By monitoring strain and temperature on different members and structures to determine strain variations caused by temperature change and live traffic, data is provided which can be used for early stage detection of issues related to fatigue or formation of cracks. Resensys structural health monitoring solutions provide SenSpot^TM data, which can also help determine load-bearing capacity of a bridge as well as detecting occasional overstrains caused by vehicles violating a bridge’s maximum allowed load. Resensys SenSpots^TM are able to monitor structural quantities such as tilt, displacement, strain and ambient temperature in concrete, steel and composite materials under wet, humid and extreme weather conditions. The products are corrosion resistant and can withstand salty environments.