Analysis Of The Method Of Adding Piers In The Mid-span To Restrain The Downwarping Of Thecontinuous Rigid Frame Bridge

As time goes on,a bridge for delivery and operation will have material aging,cracking and structural damageunder the influence of atmospheric environment,human factors,natural disasters,vehicle loads,accidents and other effect of force majeure,which will affect the carrying capacity and bring hidden dangers to the traffic safety of the bridge.Through the scientific detection and evaluation,we can find the disease of the bridge in time,and grasp the actual technical situation of the bridge as soon as possible.Taking targeted and effective reinforcement measures can improve the carrying capacity of the bridge and eliminate potential safety hazards.Scientific prevention,maintenance and reinforcement can save project investment,reduce the waste of resources and improving the life of bridge.In this paper,we put forward the reinforcement design method of adding piers in mid-span to restrain downflexing for a bridge,whichis lack ofcarrying capacity,continuous development of mid-span downflexing,external prestressing and span combination of64m+115m+64m.Firstly,the detection method,common diseases and cause analysis of continuous rigid frame bridge are introduced,which provides scientific basis for formulating reinforcement measures.The finite element model is used to simulate and analyze the actual situation of the original bridge,focusing on the influence of longitudinal prestress and vertical prestress loss on the bearing capacity.Combined with the actual material condition and disease condition of the bridge,the existing bearing capacity is evaluated and analyzed.According to the continuous deflection characteristics and bearing capacity of the bridge,a series of reinforcement schemes are designed,including adding pier column in the middle of the span,jacking up the beam body in the middle of the span and applying external prestressing outside the box.The emphasis is put on the research of adding pier column in the middle of the span and applying external prestressing reinforcement.The strength,stiffness and stability of concrete filled steel tubular latticed columns are checked,and the steering block,tooth plate and bearing platform are analyzed The checking calculation of local stress is carried out.The case study of a real bridge shows that the loss of prestress is the main cause of web cracking in the mid-span of the bridge,and the weak section stiffness and the influence of live load aggravate the downwarping in the mid-span.In the reinforcement design of continuous rigid frame bridge,the effective prestress of steel strand,material condition and structural parameters(including concrete strength,elastic modulus and structural natural frequency)should be tested.In this paper,different codes are used to design and check the new pier column reinforcement design,which provides experience for similar projects.Through the lifting of the beam body,the deflection of the beam body is artificially corrected,and the structural system is changed by adding new supports,which effectively restrain the midspan deflection.