Impact of Overweight Trucks on the Service Life of Bridge Girders

State agencies are responsible for making major decisions on allocating the available but limited funds for the maintenance and rehabilitation of bridges. Over the past two decades, the frequency of overweight trucks has kept increasing. Although the AASHTO load and resistance factor design specifications mandate a design life of 75 years, the actual service life will be affected by site-specific loading; local environmental attack, including the application of deicing salts; each agency's bridge preservation strategy; the funding situation; and routine maintenance. Nowadays, agencies issue more permits for trucks with gross vehicle weights that exceed legal load limits. There is a need, therefore, to quantify the impact of overweight trucks on the service life of bridge girders. This study presents a procedure for investigating the impact of truck loads on bridges in New Jersey through the utilization of bridge inspection reports, truck weigh-in-motion data, and the National Bridge Inventory database. Actual bridge deterioration modes in New Jersey were identified from the bridges' respective inspection reports, and the expected bridge service life was successfully correlated with truck loading from weigh-in-motion data. The deterioration mode of prestressed concrete (PC) girders was found to be the corrosion of prestressing tendons near the beam ends induced by cracking and spalling of enclosing concrete. The maintenance of deck joints is a major factor that affects the deterioration of PC girders. Additionally, a strong correlation was found between the expected service life of PC girders and overweight truck counts.