Research On Reinforcement Measures Of Additional Steel Box Tied Arch For PC Continuous Rigid Frame Bridge

With the rapid development of domestic economy in recent decades and the increasingly perfect traffic network,the prestressed concrete rigid frame bridge has been used.However,after a period of operation,many continuous rigid frame bridges suffer from box girder cracking and continuous deflection of the midspan.Based on the current status of prestressed concrete continuous rigid frame bridges in China,this paper summarizes the common diseases and causes of continuous rigid frame bridges.The damage sensitivity analysis of continuous rigid frame bridge is carried out by combining finite element method.And taking a prestressed concrete continuous rigid frame bridge as the engineering background,a relatively new structural modification system(additional steel box tied-arch)reinforcement scheme is discussed in this paper,and the basic principle and structural design of the reinforcement method of the additional steel box tied-arch system are emphasized.The major contents and innovative points of this paper are as follow:The detailed mechanism analysis of the main diseases of the continuous rigid frame bridge(beam cracking and deflection of the midspan)was carried out.The effects of prestress loss,overweight,shrinkage and creep of concrete and stiffness reduction of main beam on deflection and upper and lower edge stress of bridge are studied by finite element calculation,and the main influencing factors of the beam cracking and the deflection of the midspan are determined by transverse comparison.The current stress state and alignment of the bridge are obtained by monitoring report and testing data of the bridge.Combining with the results of damage sensitivity analysis of the bridge,combined trail calculations are performed for various damage conditions,and the reasonable combined condition is selected by deflection and stress fitting method to simulate the damage state of the bridge.The bridge damage model obtained by simulation is tested according to the standard for stress and deflection,and the results of the verification are consistent with the measured data,which provides a calculation basis for the design of the additional steel box tied-arch reinforcement scheme.Taking a diseased bridge ass the background of engineering research and referring to the norm and other related data,a reinforcement scheme of additional steel box tiedarch system is designed based on the theory of reasonable bridge completion state,and the structure and material parameters of additional steel box tied-arch system are designed.In order to improve the economy of the reinforcement scheme under thePremise of meeting the requirements of strength and deformation,uniform design method and BP neural network algorithm are used to optimize the parameters of some reinforcement members.The optimized reinforcement model is subjected to deflection and stress verification according to the specifications,and the stress and deflection before and after reinforcement are compared and analyzed.The results show that the reinforcement scheme of the additional steel box tied-arch system can effectively restrain the continuous deflection and restore the alignment of the main girder,improve the internal force state of the bridge,improve the aesthetics and service level of the bridge,and prolong the service life of the bridge.