In this paper two design examples are provided that describe how different techniques were used to accomplish the structural preservation and/or maintenance of existing bridge structures in the State of Missouri.

One example describes repair of a bridge structure that suffered damage to one exterior precast/prestressed concrete girder due to vehicular impact. From the impact, two prestressing steel tendons were fractured, resulting in approximate 10% decrease in the moment capacity. To restore the structural capacity of the girder, carbon FRP laminates were used, and restrengthening was accomplished in one single day without traffic interruption. This case study demonstrated that FRP bonded reinforcement was an effective repair technique for this bridge.

The second example describes a technique that was used for the retrofit of a bridge structure that showed significant spalling of the cover concrete and wide-open cracks in the main span bridge piers. The existing piers for the main span consist of circular boundary elements connected by shear wall panels. No transverse reinforcement was provided in the boundary elements and due to the state of deterioration of the piers it was proposed to retrofit the boundary elements with external prestressing in the diaphragm region and FRP wrapping along the entire length of the boundary elements. This retrofit technique will inhibit further development of cracks while ensuring the best possible retrofit technique for this particular bridge.