Structural Design of Main Bridge of Nanjing Xianxin Road Changjiang River Bridge
The main bridge of Nanjing Xianxin Road Changjiang River Bridge is a suspension bridge with a suspended main span of 1 760 m and two side spans of 580 m,leading to a sag-to-span ratio of 1/9 and a side span-to-central span ratio of 0.33.The two main cables(an upstream and a downstream cables),each composed of a number of 169 high-strength galvanized aluminum steel wire strands(an individual strand contains 127 steel wires of 5.4 mm diameter and gets a nominal tensile strength of 2 100 MPa),were constructed by the PPWS(prefabricated parallel wire strands)method.The hanger cables are pin-connected with the cable clamps,central buckles are added at midspan,and the short hanger cables are fitted with joint bearings.The tower-top saddles are cast-weld composite structures with wide grooves and single longitudinal rib,while the splay saddles are pedestal-type fully-cast structures.The stiffening girder,measuring 31.5 m in full width and 4 m in depth,consists of flat streamlined closed steel boxes,inside which,the top plates and U ribs are joined by double-sided submerged arc full-penetration welding.Supported by bored piles of 2.8 m diameter,the pylons are portal-frame concrete structures rising 277.3 m(full heights),the upper crossbeams are prestressed concrete structures encased with N-shaped steel plates.The south anchorage is mounted on a circular diaphragm wall foundation with an external diameter of 65 m,while the north anchorage is supported on a caisson foundation measuring 70 m by 50 m,50 m in depth.According to the static analysis,theoretical analysis of the wind resistance of the structure,and experimental studies,the strength and stiffness of the structure meet the requirements.Adding 0.67 m-deep central stabilizers and 1 m-wide horizontal stabilizers at the wind fairings allows the flutters and vortex-induced vibrations of the bridge to reach the required levels and the bridge has a degree of damping margin.
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