贵州两渡水湘江大桥主桥设计关键技术

Key Design Techniques of Main Bridge of Liangdushui Xiangjiang River Bridge in Guizhou Province

贵州两渡水湘江大桥主桥为(72+120+72)m波形腹板钢槽组合梁大跨变截面连续刚构桥。针对传统波形钢腹板组合箱梁桥底板混凝土结构自重仍然偏大、底板易开裂、下翼缘混凝土与波形钢腹板易脱离等问题,该桥主梁采用自重轻、底板抗裂能力强的波形腹板钢槽组合梁结构。主梁顶板宽20.25 m,单箱双室变截面。为解决组合梁根部钢底板受力复杂、抗压稳定性差的难题,在负弯矩区组合梁钢底板上设置混凝土层,形成顶、底板双重组合结构。为提高混凝土桥面板和钢主梁之间的抗剪承载力、有效防止桥面板横向角隅弯矩导致的竖向掀起问题,剪力连接件采用开孔钢板的双PBL键。主梁墩顶0号块采用全混凝土结构,钢-混结合段采用后承压式构造。主梁横隔板采用实腹式和桁架式两种结构形式,在提高结构抗畸变和抗扭转能力的同时,大幅降低了工程用钢量。主墩采用壁厚1.8 m的双肢实体薄壁墩。结构整体和局部计算分析表明,桥梁具有较好的安全性和适应性。

The main bridge of Liangdushui Xiangjiang River Bridge in Guizhou Province is a long-span continuous rigid-frame bridge with a main span of 120 m and two side spans of 72 m.The bridge features its steel tub girders and concrete slabs composite superstructure of variable cross-section.The webs of the steel tub girders are corrugated steel webs.In the conventional composite box girder with corrugated steel webs,the self-weight of the concrete poured on the bottom steel plates is still considered too heavy,and the cracking of the bottom steel plates and the disengagement of the lower-flange concrete and corrugated steel webs are critical issues.However,in the Liangdushui Xiangjiang River Bridge,the combined application of the steel tub girders and concrete slabs allows the superstructure to have a lighter body and the cracking resistance of the steel bottom plates to be enhanced.The two-cell steel tub girder is of variable cross-section,the top of which measures 20.25 m wide.To clarify the load bearing behavior and improve the compression stability of the bottom plates over piers,a concrete layer was cast on the steel bottom plates in the hogging moment zones,to form a double-composite superstructure.To improve the shear capacity between concrete deck slabs and the steel tub girders and effectively prevent the vertical uplift the concrete deck slabs caused by the transverse corner bending moment of concrete deck slabs,double PBL connectors are used.The pier-top segments of the superstructure are pure concrete structures.The steel-concrete joint section contains a rear load bearing plate.Both solid and truss diaphragms are employed to improve the distortion-and torsion-resistant ability of the superstructure and reduce the steel consumption as well.Each main pier has two wall-type columns,with wall thickness of 1.8 m.The global and local calculations prove that the safety and adaptability of the bridge structure is good.