Research On Rotating Construction Method And Key Structure Of Curved Continuous Rigid Frame Bridge

The rotation construction of brige is a bridge construction method which do not affect the normal operation of the traffic under the bridge.Therefore it is widly used while building bridges on existing roads or railways.In order to study the rotation construction of the curved continuous rigid frame bridge,this paper takes the viaduct of Changfeng Avenue in Wuhan(50+2×90+50)m as the research object and analyses the key structure and the stability of the construction process of this bridge.This paper mainly completes the following work:Firstly,the key construction of continuous rigid frame bridge pier,transverse frame structure and box girder curvature radius is studied.Schemes are contrasted analysed by using the finite element software.The results show that the stress distribution of multi limb double thin-walled pier is uniform and reasonable,and the displacement is also within controllable range.The force of this transverse frame structure is reasonable and the stress bending moment distribution is uniform,when the box girder with single box and five chambers is used.By analyzing the curvature radius of the box girder from 300 m to 600 m,we can obatian the lateral displacement of the largest cantilever state is-1.574 cm in the course of rotation while R=300m.So when choosing the radius of curvature of the bridge,the radius should not exceed 400 m.Secondly,the influence of rotational acceleration of 0.00012rad/s2,0.0012 rad/s2,0.012 rad/s2 and 0.12 rad/s2 on pier is analyzed.It is found that the maximum tensile stress of pier under acceleration of 0.0012 rad/s2 is 6MPa.Therefore,based on the safety considerations of the pier,the rotational acceleration of similar bridges should not exceed 0.0012 rad/s2.In the stress analysis of pile foundation of the process of rotating body,it is found that under the condition of prestressed steel bundles at the bottom of the tensioning platform,the back force of the base pile in the middle of the cap is obviously less than that of the non prestressing force,and the maximum counterforce of the pile is reduced from 11270.4k N to 9270.4k N.In group pile design,special consideration should be given to the influence of pile cap stiffness on the distribution of internal force of pile top.The method of prestressing at the bottom of the pile cap effectively coordinates the vertical displacement of the pile caps,so that the axial force of each pile tends to be consistent.Thirdly,the design method and stability of counterweight for continuous rigid frame bridge with rotating construction curve are analyzed.Wuhan Changfeng Avenue viaduct counterweight program is as follow: The longitudinal counterweight of pier 38 is as follows: the weight of each side is 1.0m long and the width is 2.0m,the weight of each side is 80 k N(q=40k N/m).The transverse counterweight of pier 38 is as follows: the counterweight is 16.0m long and the width is 4.0m..And it is arranged near the spherical hinge of the curve,and the weight is 1600 k N,q=100.0k N/m.The longitudinal counterweight of Pier 39 is as follows: the weight of each side is 4.0m long and 2.0m wide,with a weight of 180 k N(q=45k N/m),a weight of 10.0m,a width of 4.0m,a weight of 1200 k N,q=120k N/m.Three factors influencing the wind load,unbalanced weight and friction coefficient were considered in terms of stability.When the dynamic friction coefficient is less than or equal to 0.01,that is,the static friction coefficient is less than or equal to 0.017,the stability coefficient of the rotor T structure is less than 0.0815.Tilt weight(three-point support)is used at this time and the eccentricity is controlled at 5cm?e?15cm.When the coefficient of dynamic friction is greater than 0.01,ie,the coefficient of static friction is greater than 0.017,as long as the difference between the inner and outer weights of the transverse curve of the T-shaped structure is controlled within 10 t,the theoretical stability is within the controllable range.Fourthly,in order to verify the reliability of the calculation results,line monitoring,stress testing and temperature field testing were conducted on the Changfeng Avenue Viaduct(50+2×90+50)m in Wuhan.The monitoring result is that the error between the actual line shape of the bridge and the expected state is within the allowable scope of the specification,which ensures that the bridge will be smoothly closed.The final bridge alignment and internal forces of the structure are all in a safe state,which is basically the same as the calculated value and reaches the goal of construction control.