Long-term continuity moment assessment in prestressed concrete girder bridges

Use of new materials, developing new structural systems, and improving construction details while designing bridges with longer spans has been a continuous challenge for bridge engineers since early times. The study of precast/prestressed concrete (PC) bridges made continuous started in early 1960s is one of the most popular alternatives. Continuous structure improves riding comfort and durability of structure, reduction in structural depth, and reserve load capacity under overload conditions. This research presents the state-of-the-art tool for calculating restraint moments in PC continuous bridge girders. The scope of this study is limited to straight slab-on-girder bridges i.e. effects of horizontal curves or skews and bearing movements are excluded from the study. mRESTRAINT, the modified version of the original RESTRAINT program was developed to calculate restraint moments in PC continuous bridge girders with custom girder dimensions, with and without considering the diaphragm properties, individual strand data for up to up to 5-spans. Case study on a segment of Bridge #2 of John James Audubon Bridge Project demonstrates the new capabilities of mRESTRAINT program. A detailed parametric study is carried out to study the parameters that affect the restraint moment in continuous bridges. Results from the parametric study are used to study the effect of girder age at continuity factor in more depth, structural benefits from continuity, and to find a particular age of continuity based on the desired restraint moment value for a particular bridge configuration. These results may enhance the prediction/control of restraint moments in PC continuous bridge girders