Research On Treatment Of Downward Deflection Of Long Span Continuous Rigid Frame Bridge With Additional Middle Pier

As the old saying goes,if you want to get rich,build roads.As an important structure of highway,bridge is also in a state of rapid progress with the development of highway industry in recent years.Continuous rigid frame bridge is a kind of structure commonly used in bridge engineering of large span such as river and valley.However,with the increasing of the traffic volume,the continuous rigid frame bridge diseases appear frequently,which seriously threaten the operation safety of the bridge.Therefore,it is very necessary to analyze the cause of serious damage of continuous rigid frame bridge and analyze the reinforcement method based on post-evaluation.This paper takes a continuous rigid frame bridge in Yunnan Province as the engineering background,takes the main causes of mid-span flexion and the stress distribution of zero block as the theoretical basis,and takes the post-evaluation of technical status as the basis for judging the suitability of the bridge,and analyzes the reinforcement methods of the bridge.The main contents are as follows:(1)Analyze the causes of the middle deflection of the continuous rigid frame bridge,and calculate the influence of prestressed and non-prestressed loss on the middle deflection of the span.The results show that the middle deflection of the continuous rigid frame bridge is mainly caused by the prestressed loss.(2)The finite element calculation software is used to establish the solid model of the zero block,analyze the local stress of the zero block,and study the increase of the thickness of the bottom plate of the box girder and the assumption of the plane section.The analysis and research show that the overall stress structure of the zero block of the bridge is basically in a state of compression,but the four partitions in the middle have been in a state of tension,and there will be concentrated tensile stress in some areas.With the increase of the thickness of the bottom plate,the calculation error of the plane section assumption theory also increases.(3)By means of load test,combined with static load,dynamic load and vibration modal test,the theoretical analysis and measured data are compared to obtain the actual operating status of the bridge,and the technical status of the original bridge is evaluated after.(4)For the reinforcement of the bridge,three schemes are proposed,namely,adding middle pier in the middle span of the original bridge,adding cable tower and stay cable in the zero block,adding middle web and prestressed steel bundle in the middle span beam segment,and verifying the feasibility of the reinforcement and renovation schemes one by one.The calculation results show that the three schemes can meet the bearing capacity demand,and the scheme of adding middle pier has the largest comprehensive bearing capacity enrichment coefficient.(5)The natural vibration characteristics,response spectrum and dynamic time history of the above three reinforcement schemes are analyzed respectively,and the seismic response analysis values are compared.The comparison results show that the scheme of adding middle pier has the best seismic performance.