新白沙沱六线铁路长江大桥钢桁梁横断面的合理选择

Rational Selection of Cross Section of Steel Truss Girder for New Baishatuo Changjiang River Six-Line Railway Bridge

新白沙沱长江大桥主桥为(81+162+432+162+81)m的五跨连续钢桁梁斜拉桥,上层布置四线客运专线,下层布置两线货运专线,是国内首座六线铁路桥。为合理选择该桥钢桁梁的横断面,从结构的空间构成、受力及经济合理性等方面,对2片主桁与3片主桁、梯形斜桁断面方案与矩形直桁断面方案进行对比分析。结果表明:大桥采用2片主桁的矩形直桁断面方案既能满足线路的布置要求,又具有结构受力合理、钢结构制造安装方便和较好的经济性等优势。因此大桥钢桁梁最终采用2片主桁的矩形直桁断面,桁宽24.5m,桁高15.2m,上层桥面为正交异性板整体结构,下层桥面为纵横梁+道砟槽板结构。

The main bridge of the New Baishatuo Changjiang River Bridge is a five-span con- tinuous steel truss girder cable-stayed bridge with span arrangement （81 ＋ 162 ＋ 432 ＋ 162 ＋ 81） m. The upper deck of the bridge is designed to carry four-line passenger dedicated railways while the lower deck to carry two-line freight railways and the bridge is the first railway bridge to carry six-line railways in China. To rationally select the cross section of the steel truss girder for the bridge in the design, the schemes of the cross sections of the 2 main trusses or 3 main trusses of trapezoid inclined trusses or rectangular vertical trusses were compared and analyzed from aspects of the structural spatial composition, force conditions and economy rationality. The results of the comparison and analysis suggest that the scheme of the 2 main trusses of rectangular vertical trus- ses for the steel truss girder of the bridge can not only meet the requirements of the railway line arrangement, but also has the advantages of the rational structural force conditions, convenient steel structure manufacturing and installation and better economy. In such case, the scheme of the 2 main trusses of rectangular vertical trusses is finally chosen for the bridge. The steel truss girder of the chosen scheme is 24.5 m wide and 15. er is the structure of integral orthotropic plate and stringers and ballast channel slabs.