Ultimate Capacity Calculation Method of Concrete Box Girder under a Given Load Condition

Traditional method in the current codes for ultimate capacity of shallow beams is based on a selected section and a specific force condition, such as flexural capacity of mid-span section, shear capacity of Fulcrum section. The behaviour of concrete box girder is complicated, especially for its spatial effects, so traditional method is lack of accuracy. Given that concrete box girder is composed of a series of concrete slabs subjected to global effect (in-plane membrane effect) and local effect (out-of-plane bending), a new ultimate capacity method based on “plate element” is proposed. Based on layered sectional method, “plate element” can be subdivided into several “membrane elements” along the thickness direction. The ultimate capacity of the “plate element” can be deduced through a non-linear program. The new ultimate capacity method will promote the safety and sustainability of concrete box girder.