Structural Design of Main Bridge of Lunzhou Bridge

The main bridge of the Lunzhou Bridge is a prestressed concrete hybrid system of open-web continuous girder and rigid-frame with span arrangement 100 m+2×170 m+100 m.The main girder of the bridge is of twin-cell single-box section and at the meeting section of the upper and lower chords of the girder,the flexible central partition wall is employed.In the lower chord,the top slab prestressing tendons are set and in the lower chord of the root part of the girder,the web draped tendons are set.The tendons for the top slab to be cantileveredly cast are staggered in each two tendons.Before the upper and lower chords meet,the pushing force is applied and the temporary rigid fixity is made.The main piers of the bridge are the solid ones,of which the pier in the middle is rigidly fixed and the side piers will release stress.On the top of each side main pier,3 arrays of bearings are arranged in transverse direction and the temporary rigid fixing blocks are arranged as well.The segments No.0,the cast-in-situ segments of side spans and closure segments are constructed on scaffoldings while the rests of the segments are cantileveredly constructed,using the form travelers.The software MIDAS Civil 2010 and ANSYS 10.0 are respectively employed to analyze the global and local stress of the main bridge and the results of the calculation and analysis indicate that all indices of the bridge can satisfy the requirements in the codes and have certain safety margin.