Development of high performance continuity connection using CFRP composites

In Simple-Span Precast Prestressed Bridge Girders Made Continuous to improve structural efficiency partial and/or full continuity is provided through cast-in-place concrete diaphragm and decks. That is, the bridge behaves as continuous or partially continuous for live loads. The continuity connection is also beneficial from a maintenance point of view by eliminating open joints. However, existing continuity connections also have their own structural, construction, and maintenance shortcomings. Development of positive moments and diaphragm cracking at the internal pier due to time dependent effects is a major structural problem that also affects bridge durability and esthetics. Another issue is that due to reinforcement congestion, joint construction is time consuming and thus expensive. Furthermore, the degree of continuity varies depending on structural and construction conditions. These problems are common to various design details used by many states in the US. This paper discusses the development of a new continuity connection using Carbon Fiber Reinforced Polymer (CFRP) sheet that will address these problems while further enhancing structural effectiveness. To provide continuity, CFRP reinforcement is attached to the top of the girders over the cast in place diaphragm. The negative moment over the supports caused by the deck weight balances the positive restraint moment caused by creep in the prestressed girders. Thus, while increasing structural efficiency the proposed design eliminates positive moment cracking. Furthermore, there is no need for positive moment reinforcement in the diaphragm under gravity loads, thus, reducing reinforcement congestion and facilitating construction. A series of laboratory tests were carried out to validate the new connection. The results support the viability of the proposed connection and that CFRP sheet is an ideal material for continuity connections.