Optimization of prestressed concrete bridge ties for open deck railway bridges

This thesis presents a study in the optimization of prestressed concrete bridge tie design. A historical review of both the development of the bridge tie and the design of the existing tie is presented. The problem of the existing tie design cracking from rebound and the need for redesign is also outlined.; The data obtained from field investigations of a short span bridge was analyzed in order to determine the effect of various types of rail-tie and tie-girder pads on attenuating impacts from railway vehicles. Also, maximum bending strains from these impacts were determined.; A mathematical model is presented which predicts both the maximum static and dynamic strains experienced by the ties under impact. This model was then compared to the field results which led to the design of three types of prestressed concrete bridge ties.; Eighteen full scale samples (six of each type) were fabricated for laboratory testing consisting of static load tests to destruction. Measurements of strains and deflections were obtained.; The purpose of the laboratory testing was to determine the effect of increasing prestress levels in the compressive zone of the tie on the cracking moment and ultimate moment capacity of the tie. (Abstract shortened by UMI.)...