南宁市五象大桥钢箱梁施工方案比选

Comparison and Selection of Construction Schemes for Steel Box Girders of Wuxiang Bridge in Nanning City

南宁市五象大桥主桥为(45+100+300+100+45)m双塔双索面钢箱梁斜拉桥,主梁为横向分离的两全焊流线型扁平封闭钢箱梁。针对该桥钢箱梁施工难点,提出了对称悬臂拼装施工(方案1)和非对称悬臂拼装施工(方案2)2种钢箱梁施工方案,通过设备、工期及河道水位影响等方面的比选,采用方案2施工。该方案主要施工设施包括变幅式桥面吊机、边跨临时支架及顶推系统、滑移支架和桥塔墩墩旁托架及滑移系统。在边跨无水区域布置滑移支架及临时支架,安装变幅式桥面吊机,采用顶推系统后退滑移及吊机前移的方法安装边跨钢箱梁;中跨侧钢箱梁采用单侧桥面吊机悬臂拼装,利用边跨已架钢箱梁,调整索力实现非对称悬臂拼装施工。

The main bridge of the Wuxiang Bridge in Nanning City is a steel box girder cablestayed bridge with double pylons, double cable planes and with span arrangement （45＋100＋300 ＋100＋45） m. The main girder of the bridge has two all-welded streamlined flat closed steel box girders separating in the transverse direction. In the light of the construction difficulties of the steel box girders, two construction schemes of the symmetric cantilever assembling （Scheme 1） and asymmetric cantilever assembling （Scheme 2） for the girders were put forward. Through comparison of the influences of the involved equipment, construction time schedules and water levels, it was determined that the Scheme 2 should be adopted. In the Scheme 2, the construction facilities mainly included the luffing deck cranes, side span temporary scaffoldings and pushing system, sliding scaffolding, pylon pier side bracket and sliding system. In the area of the side spans not over water, the sliding scaffolding and temporary scaffoldings were arranged, the luffing deck cranes were installed and the side span steel box girders were erected by withdrawing the pushing system and forwarding the deck cranes. The central span steel box girders were erected by the cantilever assembling by the deck crane arranged on one side. By taking the advantage of the assembled side span steel box girders, the stay cable forces were to be adjusted to eventually realize the asymmetric cantilever assembling.