Deformation Analysis Of Prestressed Concrete T Rigid Frame Box Girder Bridge Strengthened By External Prestressing Tendons

A large number of prestressed concrete T rigid frame box girder bridges were constructed from the late1960s to the early1990s all over the world. However, Disease of this type of bridge such as excessive deflection at the the end of cantilever appeared with the passage of time and the development of transport. At present, the bridge is still playing an important role, so strengthening the old bridge has important practical significance.And the external prestressing reinforcement technology is one of the best methods.At present, a lot of experimental research on the limit stress of external prestressed beam has been complished, while there is little research on long-term concrete stress due to shrinkage and creep of concrete, and the relaxation of prestressed steel. Using the method of structural mechanics to calculate the deformation of T rigid frame box girder bridge and stress of structural in initial time. Then through the introduction of the T-B equation which is the relationship of screep stress and strain, the internal force equilibrium equations and the deformation compatibility conditions,an approximate analytical method, calculating long-term deflection of T frame bridge which was strengthened by straight line external prestressing tendons, was presented. This method considers synthetically the effect of shrinkage and creep of concrete, relaxation of prestressed steel and so on. Thus, a set of formulaes are established which also can compute the prestress losses of the linear external strands due to concrete shrinkage and creep, stress relaxation at any time.The newly established analysis method and the derived formulas were programmed with Fortran language. The long-term deformation of Machong Highway Bridge which strengthened by external prestressing tendons, were analyzed by the calculation program. Comparing the calculation results with the calculated results with Midas software, it shows that the proposed approximate analysis method for predicting the long-term deflection of T ridge frame bridge strengthened by linear external prestressing tendons is feasible, and the analytic formula has certain accuracy.