Prevention of Cracking in Pier Caps. Final Report

摘要

In the State of Florida, several bridges were recently found to have cracks onthe cantilever overhangs of their pier caps. If the cracks were left to grow, deterioration of the structure and ultimately failure of the caps may occur. The study was undertaken to study the behavior of bridge pier cap overhangs and to review the present Florida Department of Transportation (FDOT) design methodology, in order to suggest design modifications to control crack growth. An extensive literature review did not produce any past research work on the problem. The present FDOT design procedure for cantilever pier caps was reviewed. It was found that classical beam theory is being used by the FDOT design software. Two representative bridges were chosen as examples, and they were analyzed using commercial Finite Element programs. Actual dimensions and bridge loadings were used. Because the programs were linear, the resulting stress distributions showed good correlation with classical theories. Prototype pier caps were subsequently tested in the laboratory using simulated girder loadings. Demac points and dial indicators were used to measure deformation and deflection, respectively. Crack patterns were closely monitored. The results show that rectangular or trapezoidal pier caps behave essentially as shallow cantilever beams.