A STUDY OF BRIDGE APPROACH ROUGHNESS. FINAL REPORT

Field studies of highway bridge approach roughness, including visual inspection, measurement of approach profiles by surveying techniques and by driver evaluation, soil borings, and concrete pavement corings were conducted to determine the most important causes of approach roughness at Texas bridge sites. A literature survey identified many previously identified causes, most of which are also thought to be applicable to some of the problems observed at the Texas study sites. During the studies, repeated observations of severe cracking and dislocation of the backwalls of reinforced concrete abutments led to a detailed investigation of the causes of this damage mechanism. The observed distress is correlated to the presence of adjacent reinforced concrete pavements, and the cause is attributed to the longitudinal growth of the concrete pavements. A finite element model of a representative abutment is used to study the expected stress distributions caused by several hypothesized mechanisms which might contribute to the observed damage. Methods to prevent future damage are discussed. A model of reinforced concrete pavement is developed and evaluated. The model can be used to evaluate pavement cracking, pavement lug effectiveness, and design requirements for isolation joints to protect bridge approach slabs and abutments from pressures applied by concrete pavements.