Study On The Stress Of The Joint And In-Plane Deformation Of The Continuous Curved Box-Girder Bridge After Widening

With the rapid development of Chinese society and economy and the constant growth of road traffic volume,some roads built in the early stage can no longer meet the rapid growth of traffic demand.The lateral widening of road Bridges can not only improve the bearing capacity of Bridges and relieve traffic pressure,but also has the advantages of small area,short construction cycle and high cost performance.It has been widely applied in our country road engineering reconstruction and expansion project.According to the field investigation,some of the early widened highway Bridges appear longitudinal joint concrete cracking,support release or shear failure,expansion device failure and other diseases,which have a great impact on traffic safety and bridge service life.Therefore,it is of great engineering significance to study the force and deformation of the widened bridge structure and explore the causes of the diseases.In this paper,experimental research,numerical simulation and theoretical analysis are used to study the stress of the joint and the deformation of the horizontal structure of the widened continuous curved box girder bridge under various coupling loads.The main research contents and conclusions are as follows:(1)Based on the improved concrete shrinkage and creep calculation theory and the overall temperature effect calculation theory,the finite strip calculation program is written by FORTRAN90 standard computer language,and the stress and deformation calculation of the widened continuous curved box girder bridge under various load coupling effects is realized by Visual Studio programming software.(2)The scale model test of a two-span continuous curved box girder with one box and one room is carried out.The results show that under the action of concrete shrinkage and creep,the longitudinal strain of roof of the box girder before widening gradually increases along the outside diameter to the inside diameter.After widening,the longitudinal strain of roof of the old box girder is much less than the new box girder,the strain at the joint of the new box girder is greater than the inner wing plate.The widened new box girder spliced flanks are in tension state,while the old ones are in compression state.The results of test before and after the scaling model of a continuous curved box girder with one box and one room were compared with the calculated values of finite strip program,the correctness of the program was verified.(3)The transverse widening of a continuous curved box girder bridge is simulated and analyzed.The structural forces and plane deformation of the bridge under the coupling effects of live load,concrete shrinkage and creep,and overall temperature change are calculated.When the inner side of the bridge is widened laterally by cast-in-place construction with full support,the new beam will transfer part of its dead weight to the old beam,making the new beam structure in a favorable state of stress,while the old beam is not.When the coupling effects of lateral lateral carriageway load,concrete shrinkage and creep,and overall temperature rise are applied,the old beam is in the most unfavorable stress state.The carriageway load and concrete shrinkage and creep will cause greater tensile stress on the middle support section of the old beam roof joint.The shrinkage and creep of concrete will cause great tensile stress on the roof joint of the new beam,and the tensile stress value accounts for about 80% of the coupling effect.When the coupling effects of positive carriageway load,concrete shrinkage and creep,and overall cooling are applied,the radial deformation of widened continuous curved box girder bridge is the largest,and the effect of concrete shrinkage and creep accounts for about 78.7% of the coupling effects.When the positive carriageway load,concrete shrinkage and creep,and the overall temperature coupling effect occur,the longitudinal deformation of the widened continuous curved box girder bridge is the largest,and the longitudinal deformation gradually increases from the middle fulcrum to the beam end section,and the overall temperature effect accounts for about 88.5% of the coupling effect.(4)Based on the calculation results of the structural forces and deformation of the horizontal structure of the widened continuous curved box girder bridge under the action of various loads coupling,the forces and deformation of the bearing,expansion device and joint structure were analyzed,and the relationship between the structural forces and deformation of the widened continuous curved box girder bridge and the bridge disease was explored.The results show that the support used to widen the continuous curved box girder bridge can meet the requirements of bearing capacity,shear deformation,anti-sliding stability checking calculation,but does not meet the deflection requirements,the expansion device can also meet the horizontal beam end expansion deformation requirements,and the joint area will produce greater tensile stress,may lead to concrete cracking.In order to prevent the damage of widened back curved box girder bridge,the corresponding prevention measures are put forward.