Bridge Deck Replacement of Posttensioned Concrete Box-Girder Bridges

Abstract

This paper studies the feasibility of replacing damaged deck of posttensioned concrete box-girder bridges without the use of falsework to support the superstructure span. Parameters of the study included straight, curved, and skewed bridges, and simple versus multispan bridges. Deck replacement in posttensioned box-girder bridges requires special attention because the deck forms an integral part of the load-resisting mechanism and large precompression has been locked in by the posttensioning in the superstructure. The potential unfavorable stress reversals or redistribution during deck replacement should be carefully considered. In this study, practical options for lane closure and traffic rerouting were incorporated into the replacement strategies, and these options included temporal longitudinal and transverse replacements. Additionally, time-dependent properties for concrete and steel representatives of current construction practice were included in the finite-element model. Results indicated that full-depth deck replacement may be difficult and undesirable because the current AASHTO stress limits were violated in all four of the posttensioned box-girder bridges selected for the study. Additionally, the increase in permanent deflections through deck replacement was relatively large for these selected bridges, which is likely to result in degraded ride quality, safety, and poor drainage condition for the bridge. As a general trend, critical stresses at the top of the web and downward deflection of the girders were found to accumulate as the deteriorated deck was removed and a new deck cast.