4 ms·

Box girders in a concrete bridge are hollow, meaning a measurement system could be inside where it is dark.

• jaclaz 5y ago
  It seems to me very much (yet) theory only. From experience in actually building reinforced concrete structures (both bridges and tunnels) and following later checks/inspections the amount of dirt (be it smog, pollution, dust, spiderwebs, whatever) on a structure that has been built only a few years before is impressive and would probably make this kind of microcracks detection not feasible/ineffective, let alone via a camera (or a drone). Typically (talking of box girders where you could walk inside the bridge) you would normally check areas where you would suspect a (macro) crack to possibly develop by brushing with a hard brush the area and (not always, but it happened) pressure wash it.