Research On Typical Mechanical Problems Of Long-span Continuous Rigid Frame Bridge

Prestressed concrete continuous rigid frame bridge is an important part of so many bridge types in China, which offers lots of advantages including structural rigidity for good, smooth driving comfort, mature construction technology and so on. This bridge type is widely used in our country since the 1980s. In recent years, problems like cracks, mid-span downwarp in continuous rigid frame bridges, especially in long-span continuous rigid frame bridges are drawning general attention of the engineering.This thesis was based on the project of minjiang river bridge. We established the finite element method of minjiang river bridge with MIDAS CIVIL 2012 by considering the pile-soil interaction effect and making the main girder, pier shafts, pile foundation as a whole. The main research work is as follows:(1) List internal force and stress diagram of minjiang river bridge under construction stage, bearing capacity limit state and serviceability limit state, and calculated every single indicators of main girder according to the relevant specification. The results all meet the specification requirements.(2) The buckling analysis of minjiang river bridge was made under pier completion stage, longest cantilever construction stage and finished stage. The results showed that the first-order instability are longitudinal instability of the whole bridge under all three typical construction stages mentioned above. And the calculated buckling characteristic value all meet the relevant specification requirements. The results showed that minjiang river bridge has a certain safety stock in the above typical construction stages, and buckling instability will not occurs.(3) By analyzing the stress situation of minjiang river bridge's zero block under constant load, maximum nagetive moment and maximum positive shear working condition, we can conclude that under the influence of the above three situations, tensile stress doesn't appear in top and bottom model, compressive stress distributes uniformly, the calculated value between entity model and space pole department model is very close.(4) After analyzing the influence on the mid-span downwarp of minjiang river bridge under self-weight, longitudinal prestress loss, creep and shrinkage of concrete and main girder span-depth ratio, we can reach some beneficial conclusions. Of which longitudinal prestress loss takes the impact of the whole longitudinal prestress loss, roof longitudinal prestress loss and floor longitudinal prestress loss into account.Creep and shrinkage of concrete takes the influence of different concrete load age, different environment humidity and different reference profile into consideration.