Simulation Analysis And Optimization Design Of External Prestressed Reinforcement For PC Continuous Rigid Frame Bridge

With the rapid development of long-span PC continuous girder bridge,a series of problems have gradually appeared,which are mainly presented as the cracking of beams and the continuous deflection of midspan,which has an effect upon the normal operation of bridges.As one of the preferred technologies for continuous rigid frame bridge reinforcement,the principle of externally prestressed reinforcement can effectively increase the bearing capacity of the structure,improve the midspan deflection and increase the compressive stress reserve of the main girder.Although the external prestressing reinforcement method has been widely used in bridge reinforcement projects,there are still many problems to be studied at present.Based on the engineering background of the Luonan Bridgethe,in this thesis,the main diseases and causes of formation the continuous rigid frame bridge are analyzed,and the the bridge diseases are simulated.On the basis of this,On this basis,the rational layout of the steering block is studied.According to the stress distribution in the anchorage zone,the corresponding optimization scheme is adopted to improve the force of the region.The main contents are listed as follows:(1)The development,the existing diseases and the causes of the diseases of prestressed concrete continuous rigid frame bridge at home and abroad were discussed,and the present situation and the existing problems of the method of external prestressing reinforcement are discussed.(2)The basic theory and calculation method of external prestressing reinforcement were discussed.It is mainly for the calculation of ultimate strength and normal serviceability limit state of flexural member by external prestressing,and the construction and calculation of anchor block zone and steering block.(3)The actual state of PC continuous rigid frame bridge before consolidation is simulated and the study of the steering device along the longitudinal position of the bridge are carried out.The environment of background engineering is simulated by finite element software Midas Civil,to analyse various possible adverse factors like the longitudinal direction prestress loss on the roof,floor and web,the adjustment to the creep coefficient of concrete beam and crack of beam which influence the bridge deflection.Compared with bridge deflection current situation,the range of deflection impact factors are analyzed quantificationally,and the mode of lengineering background is fitted out before reinforcement.At the same time,according to the simulation model,the alignment of the external beam is changed by the different positions of the steering device along the longitudinal bridge,the most reasonable position of the top and bottom steering block is obtained by analyzing the influence of the location of the steering block on the deflection and stress of the continuous rigid frame bridge.(4)The stress of anchorage zone is analyzed,and corresponding measures are put forward for stress concentration problems.Combined with the background engineering,local model of steel anchorage device and the adjacent section of the beam are established by finite element software Midas FEA.The stress distribution of the anchorage device itself and the beam of the anchorage section is analyzed.Two schemes are designed for the anchorage system and the weak area of the main beam,and the influence of the stress and distribution of the stress with the two optimization scheme is analyzed.(5)Based on the model before the bridge reinforcement,the process of external prestressed reinforcement is simulated and analyzed,and combined with the actual construction monitoring data to analyze the reinforcement effect.