As the U.S. transportation structure ages, the need to develop, use, and implement load rating methods and procedures becomes even more important. In this context, this project focuses on concrete bridges designed prior to the nationwide adoption of AASHTO LRFD Bridge Design Specifications (BDS) first published in 1994 and required to be used in new designs in 2007. Because the current AASHTO LRFD BDS have shear design and detailing provisions that are stricter than the older AASHTO Standard Specifications, girders of the older bridges typically do not meet the requirements of the current specifications. The load carrying capacities of existing prestressed and non-prestressed concrete bridges have to be evaluated by departments of transportation (DOTs) to ensure public safety as shear failures can occur with little to no warning and signs of shear distress may not be visible during periodic inspections. Currently, DOTs evaluate older bridges using methods, such as the Modified Compression Field Theory, that were developed for design purposes. Existing laboratory test data show that the method is appropriate for calculating the capacity of modern bridge members designed according to the current specifications. However, there is a significant lack of data on the capacity and behavior of concrete members that have reinforcing details that are not compliant with the current specifications. Moreover, data is lacking on members that have sizes, cross-sectional shapes, and material grades that reflect actual design and construction practices.
The objective of this research is to gather data and knowledge on large-scale prestressed and non-prestressed concrete girders designed using older versions of AASHTO specifications and therefore may not meet current shear detailing requirements of AASHTO LRFD. This knowledge and data will be used to develop calculation methods and procedures that will aim to be accurate and sufficiently conservative in evaluating the shear capacities of prestressed members in existing bridges.
