Photo Credit: Alex Mead
Seen here are two piers of the I-75 bridge over the Rouge River in Detroit, Michigan. The four columns support the entire weight of the bridge above and carry the load to the foundation under the surface of the water. As a result the piers need to be protected from potential impacts with vessels traveling on the water. To protect the piers engineers design barriers made of numerous logs driven into the bottom of the river bed. These barriers are then bound together with loops of steel cable. By binding the logs together the strength of the barriers greatly increases.