Implementation of the Negative Moment Reinforcing Detail Recommendations

Project status

In progress

Start date: 05/01/17
End date: 04/30/21


Principal investigators:

Co-principal investigators:

About the research

Prestressed concrete girder bridges have historically been designed with negative moment reinforcement in order to resist loads after full continuity is achieved. The Iowa DOT Office of Bridges and Structures Bridge Design Manual calls for additional longitudinal, so called b2, bars for resistance to negative moments caused by super-imposed dead loads and live loads. In an attempt to determine if current negative moment reinforcement requirements are overly conservative, a previous study performed by the researchers found that the amount of so-called b2 reinforcement for negative moment regions of prestressed girder bridges may not be needed to the level currently specified. This finding is particularly important because current design approaches were indicating that increasing amounts of reinforcement were needed--causing both construction difficulties and increasing overall bridge costs.

The goal of this project is to evaluate the performance of a yet-to-be-constructed bridge on E-57 over I-35 that utilizes both current b2 amounts and the proposed reduced amounts. This would allow for the comparison of the behavior of sections with varying amounts of negative reinforcement present to help determine what requirements are necessary in the negative moment region of prestressed concrete girder bridges.



  • Iowa Department of Transportation
  • Iowa Highway Research Board