Civil infrastructure heavily impacts economic and societal growth, with bridges being an integral part of joining highways and crossing impassable terrain. But a large portion of these bridges in North America were built during the post-World War 2 economic boom, before rigorous safety standards were put into place!
These bridges were not built to last indefinitely, and are slowly but inevitably failing after standing for almost 70 years. The American Road and Transportation Builders Association found that nearly 10% of American bridges are substandard, and the National Research Council of Canada found in 2013 that 30% of highway bridges in Canada are structurally deficient, which doesn’t necessarily mean they’ll collapse any moment, but does mean that they are in desperate need of maintenance.
Bridge inspection is one of the major components of maintenance. It determines what exactly needs to be repaired, as well as the equipment and processes required.
An efficient bridge inspection procedure helps eliminate unnecessary expenses by clearly indicating what elements of the bridge have specified issues and what repairs will be required.
There are several levels of inspection, depending on the needs of specific bridges.
Visual inspection, commonly performed bi-annually, involves checking the general condition of the bridge, assessing materials and elements, and identifying repairs needed.
General maintenance inspections are performed every spring and fall, and function to check if there are safety issues and call in repair crews immediately if required.
Roadway inspections deal with the road, and the team will call for a more detailed inspection if potential safety hazards exist.
Emergency inspections take place after events that directly impact the bridge, including collisions and natural disasters.
Inspectors have a number of different technologies to locate and characterize defects in bridges. They primarily use cameras and their own eyes to assess defects, but on occasions where surface inspection is insufficient, ultrasonic or magnetic tools, for examples, can provide some information on subsurface conditions.
For Ontario, the Ontario Structure Inspection Manual (OSIM) dictates the procedures and requirements for inspecting bridges. It’s a 400 page document that details everything necessary to inspect a bridge, from when to label a concrete surface as “poor” to what equipment should be used for underwater inspections. The OSIM is one of the most developed bridge inspection standards in Canada.