Research Of Reforcing Techology Of Transforming T-shaped Rigid Frame Bridge To Continuous Rigid Frame System

Due to the characteristics of determinate structure in T-shaped rigid frame bridges,the negative moment in pier girder consolidation and vertical deflection in connection of bracket and cantilever increase sharply.There will be damage of support,crack of leg and shift of beam,especially the live load deflection may cause bumping at bridge head and damage of expansion joint,so there may be much maintenance and reinforcement,but the effect is bad.With the increasement of the traffic volum and the increasement of the transport loads,the capability of the bridge will not be fit to the transport condition.This thesis takes the method of transforming structure system,to research the feasibility of transforming T-shape rigid frame bridges to continuous rigid frame bridges,and the concomitant solution.This thesis discusses the basic thinking and structure of transferring T-shaped rigid frame bridges to continuous rigid frame system,which refers to replace concrete hanging beam to steel box girder,and to link steel box girder and the old prestressed concrete cantilever beam.This thesis focuses on a background bridge,uses Midas Civil to build the spatial beam finite element model,and analyses the characteristics and differences of stress,discuss the possibility of transform.Basic on the structural calculation,the conclusions are as follows:(1)After transferring T-shaped rigid frame bridges to continuous rigid frame system,there will be positive bending moment in the middle of the bridge(in the old hanging beam and part of cantilever beam),but the negative bending moment will be smaller,besides,there will be tensile stress in bridge floor,and there will be insufficient bearing capacity;(2)the rigid of the structure will be improved after transferring the system,which improve the live load deflection;(3)the moment in pier will be smaller in live load,but it will be larger in temperature load;(4)vibration frequency of structure will be improved,and improve the dynamic performance;Above the aforementioned analysis,the reasonable structure design can realize the reforming of structure,but it should need extra reinforcement design,some calculation and reinforce.To realize the purpose,this thesis compare the tensioned external prestressing steel method and paste steel plate method.Firstly,this thesis does the primary design of external prestressing steel and paste steel plate,discusses the principle,the shape,the anchorage,the deviator of external prestressing steel.And then does the analysis of pasting steel plate,discusses the places,number,section of the steel plate.Pasting steel plate is more convenient to apply,Compared to external prestressing steel.This thesis also researches the link structure of steel box girder and the old cantilever beam,and point out the resolution of using high strength bolt to consolidate the two parts,and sets rear bearing plate,to form the steel-concrete transition part.The pretightening force in high strength bolt will make the steel and concrete more close and,and the friction will transit the force.At the same time,screws will bear shear force.Because steel-concrete transition part is important,and it is hard to reform bracket,the design sets vertical bolts.At the same time,it should pour concrete between rear bearing plate and steel box girder,to avoid the local deformation in bearing plate.Finally,this thesis researches the applicability of the method.By the method of parametric modeling,the software builds many different span,height model,and do the correlation analysis.When the main span is determined,negative bending moment in root of beam and the positive bending moment in end are linear with the length of cantilever and height of pier;the bending moment in bottom of pier is linear with the length of cantilever,and linear with the square of height of pier.