渝黔铁路新白沙沱长江特大桥主桥设计关键技术

Key Techniques for Design of Main Bridge of New Baishatuo Changjiang River Bridge on Chongqing-Guiyang Railway

新白沙沱长江特大桥主桥为(81+162+432+162+81)m的铁路钢桁梁斜拉桥。大桥采用双层桥面,上层布设4线客车线,下层布设2线货车线。通过方案比选,确定钢桁梁采用制造简单、安装方便的2片主桁矩形断面方案。2片主桁的每根竖杆处均设三角形桁架式横联,其与上层桥面的横梁以及下层桥面的竖向和斜向吊杆组成强大的横向传力体系。下层桥面通过设置制动撑架确保纵梁的连续。采用并置平行钢丝斜拉索,以满足单点索力18 000kN的受力要求。索梁锚固采用双索锚固整体双锚拉板+锚箱的复合式结构,索塔锚固采用环向预应力结构。制定了大桥6线铁路的强度加载标准和疲劳加载标准。采用多重减重措施,将桥梁的恒载由107t/m降低至97.5t/m,减少了用钢量。

T he main bridge of the N ew Baishatuo Changjiang River Bridge is a railw ay steeltru ss girder cable-stayed bridge w ith span arrangem ent （81 ＋ 162 ＋ 432 ＋ 162 ＋ 81） m. T he bridgeis designed as a double-deck bridge. On the upper deck of the bridge, 4 tracks for the passengertrains are arranged while on the low er deck, 2 tracks for the freight trains are arranged. A ftercom parison of the different schem es, it is determ ined that for the steel tru ss girder of the bridge,the schem e of the rectangular section girder of 2 main trusses that has the advantage of sim plem anufacturing and convenient assem bling should be adopted. A t each vertical m em ber of the 2main tru sses, a lateral bracing of the triangle tru ss type is arranged and together w ith the nearbycross beam s of the upper deck and the vertical and diagonal m em bers of the low er deck, the lateralbracing constitutes a strong lateral load transferring system . By arranging the braking bracings onthe low er deck, the continuity of the longitudinal girder can be guaranteed. T he tw in parallel steelw ire stay cables are used so that the load bearing requirem ent of the 18 000 kN stay cable force ata single point can be m et. T he anchorage in the main girder is the com posite structure of the integraldouble anchor tensile plates ＋ anchor box for anchoring each tw o stay cables and the anchoragein a pylon is the structure th at is prestressed circum ferentially. T he loading criteria for thestrength and fatigue of the bridge to carry the 6-track railw ays are form ulated and by taking them ultifold w eight reducing m easures, the dead load of the bridge is decreased from the 107 t/m to the 97. 5 t/m and the usage amount of the steel is consequently reduced.