Anchorage Requirements for Grouted Vertical-Duct Connectors in Precast Bent Cap Systems

Bridge projects constructed in Texas which utilize precast bent caps typically employ grouted vertical ducts in the cap-to-column connections. This type of connection is preferred due to the simple geometry and because the volume of grout needed to complete the connections is minimized. A number of questions related to the sensitivity of the behavior of the grouted vertical-duct connectors to design parameters were identified during the design and construction of these bridges.

Thirty-two, large-scale pullout tests of connectors grouted in galvanized steel and plastic ducts were conducted to investigate the response of this type of connector. The results indicate that the tensile capacity is sensitive to the type of duct, the embedded length of the connector, the number of connectors tested simultaneously in tension, and the placement of the connector within the duct. However, the results were not sensitive to epoxy coating on the connector or to the presence of spiral transverse reinforcement around the group of connectors.

Design equations are proposed for the minimum embedded length of all connectors to satisfy serviceability concerns and for the development length necessary to resist the calculated tensile stresses in the connectors under the design load combinations.