Accelerated Testing for Fatigue Crack Resistance of Pavement Systems on Orthotropic Steel Bridge Decks

The major cause of failure of pavements on orthotropic steel bridge decks has been fatigue cracking of the pavement over the points of attachment of the webs of the longitudinal stiffeners to the steel deck plate. Accelerated constant load fatigue tests on composite (deck plate and pavement) flexural fatigue beams have been used to compare pavement systems and to predict service life. However, accelerating the tests to provide useful information in a reasonable time frame requires that the load frequency or load level, or both, be substantially increased beyond service conditions. If the load is increased too much, permanent distortion of the specimen may result, thus making the test no longer a fatigue test. Increasing load frequency too much may overheat the test specimen. Since pavement stiffness decreases as its temperature increases the temperature increase reduces the stresses that cause the fatigue cracks. This paper discuses these potential problems and presents test results to help define the limitations of accelerated fatigue tests for orthotropic steel deck pavements.