Bottom continuity tendons induce transverse additive effect while providing longitudinal compression during the construction of PC box girder. Taking a cross-sea bridge for example

the mechanism of bottom continuity tendon is investigated. The transverse effect and parameters study are conducted through a refined model. It is illustrated that the state of bottom flange is in a dynamic changeable process during the tensioning of bottom continuity tendons

and the transverse effect caused by the tendons is much more than that by dead loading and other prestressing tendons. The transverse effect is more sensitive to alignment and thickness of the bottom flange

as well as concrete cover of the ducts. Finally

based on the simplified frame analysis

the design method is proposed by introducing prestressing effect simplified factor and duct modified factor.