*5.1.2 Deterioration from overloading*

The effect of heavier truck loads on today's bridges, which in many cases were designed over 50 years ago, produces an element of deterioration on the bridge deck and supporting components. Increased truck weights, volumes and speeds produce more cycles of larger stress ranges reducing the fatigue life of beams and girders. The longitudinal and vertical forces induced by heavy trucks tend to exacerbate the deterioration of the bearings, which are already weakened by salt-laden water and debris. An additional problem is many existing bridges lack sufficient grillage reinforcement which results in cracks and spalls on the abutments and piers near the bearings. If the bridge approach slabs are insufficient the impacts of heavier trucks hitting the bridge produce higher incidents of cracks and spalls of concrete header and back walls at the abutments [7].
