Accelerated Bridge Construction (ABC) technologies are changing the ways State Departments of Transportation (DOTs) do business. Subsequently, a three-phase project on the Rapid Bridge Deck Joint Repair Investigation is originated with the Iowa DOT. Phase I of this project focused on documenting the current means and methods of bridge expansion joint maintenance and replacement, and then identifying improvements. Based on the findings from Phase I, Phase II focused on the concept development. It was decided that a desirable approach would be to develop a design to move the joint away from the bridge deck at the face of the abutment to the approach slab that acts as a transition between roadway pavement and the previously mentioned bridge deck. By using this concept, a more effective joint can be created, where possible deicing chemical laden water leakage on the substructure components is no longer a concern for deterioration and its construction time can be comparable to that required for traditional joint replacements.

Phase III is tasked with the further development of this concept, the deck over backwall concept. The research team proposed various joint detailing options taking numerous factors into account. With this information, the Iowa DOT developed a more detailed joint considering their construction practices, experiences, and preferences. Full-scale finite element (FE) models of two different bridges were realized. These models were analyzed with various loading conditions from dead loads, temperature loading, and live loads which corresponds to various truck loading conditions. Both models were validated using the original drawing plans and the American Association of State Highway and Transportation Officials (AASHTO) Specifications providing deflection limits for vehicular bridges in the absence of other criteria. The impact of the deck over backwall concept on the existing bridge elements was studied with the FE models alongside a parametric study of various bridge skew angles. The concept along with the approach slab were modeled in the FE models. Results show an increment in bearing loads due to the dead loads and live loads alongside relevant deflection values and stress levels at certain points of interest across the new joint and approach slab.

A cost estimate of different types of joints including the deck over backwall concept was developed. An initial estimate of the construction cost of the concept was realized to be used in the overall cost estimate. Results show that the deck over backwall concept over a bridge service life of 25 years constantly ranked 3th or 4th out of the nine types of joints that were considered. Over a bridge service life of 50 years, the concept produced the lowest cost in all possible combinations of inflation rates and fluctuations in installation cost and joint service life. In average, a break-even point (BEP) of 44 years was determined with a 2% interest rate and lowers as the interest rate is increased.

An experimental investigation plan was realized with the Iowa DOT joint. Test results will be compared and correlated with the FE models. A plan for construction observation and post-construction testing was developed with an instrumentation plan and various real-life truck loading cases to be correlated with the FE models. Implementation of the deck over backwall concept and the post-construction plan is expected to be conducted in a future Iowa DOT construction season.

With the results obtained from the FE models and, in the future, with the experimental investigation and the post-construction testing, the Iowa DOT can confidently design and further develop the deck over backwall concept.