Quick-Strengthening Method Of Transforming Simply Supported Into Continuous System For Existing Railway Bridges

Bridge plays an indispensable role in railage as an important part of railway line in our country, and most of them are divided T-beam bridges. The bridges’transvers stiffness is weak, and the original design maximum speed is far below that of high speed trains. The unprecedented burdenhas been taken on the railway bridges from heavy trains. At the same time, the bearing capacity of existing bridges is not enough with prestressing loss and over load operation in transit, the deflection and dynamic response are too excessive. Some static and dynamic index exceed the specified values of "Code for rating existing railway bridge" repeatedly.To solve the problems such as the weak transverse stiffness, excessive deflection and so on, four composite strengthening methods are proposed which may change the support system, use external prestressed strands and precast concrete transverse diaphragms. The 32m-span prestressed concrete double T beam railway bridges are chosen for modeling in this paper, and the transverse diaphragms’thickness of these methods are considered. Based on the results of natural vibration properties analyzed by Ansys finite element software, the optimized strengthening method is recommended.The multi body dynamic software UM is used for calculating the dynamic response of bridges before and after strengthening.Then the dynamic response of bridges before and after strengthening under the high speed trains and heavy trains with different velocities is calculated. The effects of Rayleigh damping parameters and track irregularity to vehicle-bridge coupled system are considered in the process.The calculated results prove that the effect of selected method is obvious. The bearing capacity and natural vibration properties are increased and the dynamic response is decreased observably.