Study On Shear Deformation Of Segmental Joint And Its Influence To Deflection Of Continuous Rigid Frame Bridge

Continuous rigid frame bridge, as a form of the prestressed concrete box girder bridges, has been designed and constructed widely in domestic in recent decades.lt has inherited many advantages of the continuous beam bridge and T-rigid frame bridge,such as:the continuous beam and bridge deck with fewer expansion joints,the fixed beam and pier top without supports,the construction without system conversion.So whether in aspect of the difficulty of construction or in aspect of the behavior in usage period, continuous rigid frame bridge has a better performance than other similar bridges.However,the excessive deflection of mid-span section and a lot of crack in the surface of box girder was found by the inspection of constructed bridge.The causes which lead to too much deflection of mid-span section are very intricacy, which mainly include the reduction of the effective prestress,the shear deformation and creep of segmental joints,the excessive load of usage period,the defects of construction and design.The laws of deflection of continuous rigid frame girder during construction phase and use phase are studied in this thesis,which are caused by the shear deformation and creep of segmental joints.The studied content of this thesis are as follows:1) During the beam cantilever construction process,along with the increase of the cantilever length,the influence of deflection caused by shear deformation of the segmental joints is studied;2) During usage period,according to the two calculation modes of concrete creep proposed in1985and2004, the influence of deflection caused by shear creep of the segmental joints is studied in different age of calculation;3) During usage period, along with the increase of shear creep of the segmental joints,the laws of deflection of continuous rigid frame girder is studied;4) During usage period,after the shrinkage and creep of concrete completed, along with the reduction of the effective prestress,the laws of deflection of continuous rigid frame girder is studied.Based on the analysis above mentioned,the main achievements are as follows:1) During the construction phase, the influence of cantilever deflection caused by shear deformation of the segmental joints is little; 2) During usage period,the beam deflection increment calculated by85bridge code is bigger than the one calculated by04bridge code.whereas,both the85bridge code and04bridge code are lack of consideration to the long term and the degree of influence of the shrinkage and creep of concrete;3) During usage period, along with the increase of shear creep of the segmental joints,the laws of deflection of continuous rigid frame girder is nonlinnear;4) During usage period, along with the reduction of the effective prestress,the deflection of continuous rigid frame girder is growing.So the pre-camber of continuous rigid frame bridge should be multiplied by a coefficient which was greater than one to consider the influence of shear deformation when it was designing.