1 Project overview XX Bridge is located at the junction of Dongshan Town, Yuhua District, Changsha City, and XX Town, Changsha County. It is a combination of urban and rural areas. The route starts from Huahou Road, passes through Dongshan Town General Pump Plant, and crosses Liuyang River to connect with Guangda Road. Yangtuo Bridge and Liuyang River Bridge of Airport Expressway are respectively built 4.8km upstream and 8.0km downstream of Liuyang River at the bridge site. The terrain is flat as a whole, the west bank is steep, the top elevation of the embankment is 40.14m, the east bank has a wide floodplain, the top elevation of the flood embankment is 41.12m, the bottom elevation of the river bed is about 24.30m, and the maximum height difference between the top of the flood embankment and the bottom of the river bed is 17.0m. The superstructure of the main bridge is 32+2 × 50+32m variable cross-section prestressed concrete continuous box girder, which is in the form of single box double chamber section, with the top width of 18.5m and the bottom width of 12.0m, The cantilever plate on the flange is 3.25m long; the root beam of the box girder is 3.0m high, and the mid span beam is 1.4m high. The lower edge of the beam body changes as a parabola, and the curve equation is Y=1/7 X-1/31500 X? , side