NCHRP Report 519., Connecting Simple-Span Precast Concrete Girders for Continuity, contains the findings of research to develop recommended details and specifications for the design of continuity connections for precast concrete girders. Examples illustrating the design of four precast girder types made continuous for live load were also developed.
Many states make precast, prestressed girder bridges continuous using a cast-in-place connection between girders over the piers. Compared with simple-span bridges, continuous bridges require less expansion joint maintenance, have improved seismic performance, and have reduced bending moments. Although bridges constructed in this fashion have been in service for many years in a number of states, there had been limited verification of the ability of the connection to provide predicted continuity. As a result, some states design the girders as simple spans for both dead load and live load, neglecting any moment resistance of the connection.
The objective of this project was to recommend details and specifications for the design of durable and constructible connections that achieve structural continuity between simple-span precast, prestressed concrete girders. The report's recommendations are based on experimental verification of the effectiveness of the continuity connection, considering significant variables such as concrete placement sequence, reinforcement details, concrete properties, diaphragm cracking, and beam depth. Specifications and connection details to achieve the full benefits of continuity are recommended based on physical testing and analysis