Analysis On The Reasonable Bridge Completion State Of Multi-span PC Continuous Bridge During Design And Construction Stages

Multi-span prestressed concrete(PC)continuous bridges with the advantages of large stiffness,small deformation,driving smoothness are often used for important projects across the ocean or large river bodies.To restrain the long-term downwarp of the main beam,reasonable completion state of the bridge will be discussed in terms of design and construction processes.In this paper,taking a strait bridge in Fujian as a background project,one of the leagues with span arrangement was studied.With the aid of the finite element modelling software Midas/Civil,combined with field monitoring data,set bridge internal force and curvature state as the main focus,the following contents will be analyzed for the purpose of providing reference of future similar projects:(1)Design phase based on reasonable bridge state according to the load balance coefficient method in key section prestressing tendon tensioning arrangement of the T-shape cantilever steel beam structure were analyzed according to the "longitudinal-vertical—transverse" and the"vertical-longitudinal-transverse" tensioning sequence of both "two phases tensioning of long strand first and short strand second" and "simultaneous tensioning of long and short strands" and its influences on the construction and bridge completion state.The most reasonable prestressing tensioning scheme was proposed based on the two tensioning sequences.(2)With respect to the construction stage,theoretical calculation principle of temperature load was introduced,and the influence of temperature on the construction and the completion state of the bridge was analyzed.The influence of gradient temperature difference on the internal force and deflection of the cantilever was emphatically analyzed.Combined with the local meteorological data,several suggestions on the temperature control in the cantilever casting and closure process were given.(3)The influence of the weight of two hanging brackets,the order of closure and the timing of temporary joint removal on the bridge completion state was analyzed.65t triangular hanging bracket and 77t diagonal hanging bracket,symmetrical closing of first even and then odd spans,adjacent closing of first even and then odd spans,temporary joint on one side close to the fixed support removal before the prestressing tensioning of the closing section,no temporary joint removal and removal of the temporary joint on the other side after the prestressing tensioning.Considering different construction schedule schemes,and at the same time,verified the bearing capacity and stability of the hanging bracket as well as the influence of temperature on the timing of temporary joint removal.