Research On Key Issues For Construction Controling Of Long-span Suspension Bridges With Steel Truss Girder

Several key technologies of construction control of long-span suspension bridge with steel truss girder was studied based on the practical experience from the construction control of 730m YunNan JinDong Suspension Bridge with steel truss girder.The contents and achievements are as followed:(1)The structure characteristics and the application occasions of suspension bridge with steel truss girder was analyzed and the content of monitoring of JinDong Bridge was made up.(2)The alignment of cable under self-weight and static load were calculated,using the segmental catenary method.The mechanical and geometrical relationships between adjacent cable nodes,the positions of saddle and tangent point,etc.,were considered.The key technique in the construction control of datum strands and other ordinary strands were researched respectively,taking the actual temperature of the site,the actual saddle position into account.The manufacturing unstressed length of the steel truss girder was calculated,and conclusions implied that the steel truss girders of JinDong Suspension Bridge can be manufactured according to the alignment under required loads.(3)According to the features of the JinDong Bridge,the cable tension of anchorage under self-weight was calculated firstly,then the tension under dead load should be checked to meet the requirements.The thermal influence coefficient of cable tension in anchorage was calculated respectively when the splay saddle was fixed and free.When the splay saddle was fixed,the needed temperature corresponding to the slip of the cable in saddle was calculated,providing instructions for the construction.Besides,seven different formula of natural frequency of cables and its error analysis were deduced.Through the field test,the cable tension measurement and adjustment were completed.(4)Based on the actual alignment under self-weight and dead loads,under the condition that the spacing of slings are constant,the new shape was calculated,then the clamps' positions and slings' lengths are recalculated.Also,the method of locating cable clamp was introduced.The finite element model of suspension bridge with cable clamps was established,and it' s found that the cable curve rose a little,and the length of slings increased accordingly,and the cable clamps have effect on the construction process.(5)Considering that secondary dead load were massive with concrete decks accounting for 44.1%of the total dead load,the connection mode of different segment,the erection sequence of truss girders and concrete slabs were analyzed.The reasonable construction scheme were given:Interval hinges were used among segments,and these hinges became rigid connection when the angle of bottom chord bar became zero.The girders were erected from the mid-span to the bridge tower.When the cable crane system was permitted,the concrete decks were also erected from the mid-span to the bridge tower.In the lateral direction,the slabs were installed phase by phase,with numbers increasing in a sequence of 2,4,6 and 8.The car cranes could also be used for shorter construction period,and the concrete decks were erected from the bridge tower to the mid-span.In the lateral direction,the decks were installed to form a channel with 4 slabs firstly.After the closure of the channel,the remaining decks were installed from mid-span to the bridge tower.