Study On The Control Technology Of Long-span PC Continuous Rigid Frame Bridge

PC continuous rigid frame bridge has become type of a competitive bridge within 100～300m,because of its good structure load performance,fewer expansion joints,comfortable trowel,modeling succinct aritstic,less maintenance and so on.However,at present,PC continuou,s rigid frame bridge also appeared a variety of diseases in the course of operation,one of a major disease is excessive midspan deflection and more common.Aiming at the problem of over-midspan deflection of PC continuous rigid frame bridge,based on the analysis of the causes of its disease.Based on Long Yong high-speed Rock Creek Bridge in Hunan Province(span arrangement is 116+220+116m),the sensitivity analysis of some factors that cause the midspan deflection is carride out and the control measure to improve the continuous deflection of Continuous Rigid Frame Bridge is proposed.The main contents and achievements of the study are as follows:(1)The paper has analyzed the influence of the calculation model of Shrinkage and creep of concrete,the rigidity of box girder,and loss of prestress on midspan deflection of PC continuous rigid frame bridge by contrast.It is found that the effect of Loss of Prestress on the mid-span deflection is more significant.(2)The effects of temporary external beam tension on the beam stress and mid-span deflection during the construction of 3#,7#and 14#beam sections were compared.The results showed that the temporary external beam was applied to improve the stress and reducing the effect of mid-and long-term torsion is obvious,which can increase the compressive stress of the middle and lower edges by 41.21%in mid-span.(3)In order to improve the effect of temporary in vitro beam tension,the temporary external beam is optimized by changing the tension time and the length of the temporary external beam,and the calculated results are compared with the original design.The time and tension length of the extracorporeal bundle were obtained.(4)The study was carried out by increasing the top plate reserve beam and the midplane floor reserve beam to control the midspan deflection.The effect of the top plate pre-set beam and the mid-span floor stay on the mid-span deflection is compared with the position of the top plate and the mid-span deflection.The position of the top plate reserve beam and the mid-span floor reserve beam with the highest efficiency of controlling the mid-span deflection;Influence of tensioning roof prestressed bundles and mid-slab prestressed bundles on transverse deflection and beam stress at different time.Come to a more reasonable tension time;The effect of different number of roof strands and the midplane blanks on the mid-span deflection and the stress of the beam is increased,and the reasonable amount of tension in the compressive stress of the beam is obtained.(5)The effects of the two schemes on the stress and deflection of the two systems are compared.The results show that the effect of improving the stress and deflection of the midplane is more it is good.