About the research
Increased and heavier traffic loads and the effects of harsh environmental conditions contribute to significant deck distress in post-tensioned box-girder bridges in California. The deck in several of these bridges is expected to be in need of repair, rehabilitation, or complete replacement in the not too distant future due to concrete fatigue, freeze-thaw damage, and/or the potential for experiencing punching shear failure. Since the deck forms an integral part of the superstructure load resisting mechanism, a special approach is required for repair, rehabilitation, or replacement the deck in box-girder bridges.
However, to successfully develop such an approach, which involves localized partial deck concrete removal and replacement with UHPC that has thixotropic and rapid set properties, further investigation is needed to:
- Determine, through detailed finite element modeling, the nature and magnitude of stresses that would develop following the removal and replacement of a thin layer in the deck of single span, two span, and/or multi-span continuous bridge structures.
- Determine the maximum acceptable depth of removal and replacement of the existing deck concrete as a function of location and/or area such that the required structural section properties of the box in its final configuration is not adversely affected assuming no supplementary or temporary support requirements during construction.
- Identify any special concerns that may develop from the changes of both deck and girder section properties during partial depth removal/replacement such as creep and shrinkage effects, shear transfer between old concrete and UHPC, positive/negative flexure, and resistance to punching shear.
- Improve the understanding of and establish estimates for the fatigue and long-term effects on the bond between both old existing concrete and partial depth deck patch and the UHPC overlay, particularly under service loads, through testing of large-size box-girder bridge deck overlaid with UHPC.
The goal of this research is, therefore, to develop the knowledge needed to establish a suitable methodology for the rehabilitation of post-tensioned box-girder bridge decks on California using the UHPC overlay concept by:
- Numerically investigating the effects of rehabilitating the deck on post-tensioned box-girder bridges using UHPC layers that involve partial depth removal and replacement of deck concrete for different bridge configurations
- Determining the effects of a UHPC overlay used in a deck rehabilitation application on both local deck and global girder section properties of post tensioned box-girder bridges
- Investigate the long-term durability of bond interface between the old concrete and UHPC
- Developing design details, design guidelines with examples, construction specifications and quality control plan for application of UHPC overlays and proof-testing of a full-scale laboratory mockup with and without additional reinforcement in the UHPC layer, which will be suitable for use on a field trial pilot project to be conducted in a future study