勐古怒江特大桥主桥斜拉桥钢箱梁设计难点

Difficulties in Design of Main Bridge Cable-stayed Steel Box Girder of Menggu-Nujiang River Grand Bridge

勐古怒江特大桥主桥为云南省首座双塔三跨空间扇形双索面钢箱梁斜拉桥,主梁采用分离式扁平流线型钢箱梁。结合主桥施工特点,采用梁单元模拟计算主梁结构在各阶段的第一体系应力包络,板壳单元计算第二体系应力;主桥钢箱梁内外隔板受力复杂,分别建立标准段和梁端压重段局部模型,进行受力分析;斜拉索梁端锚固区钢锚拉板受力集中,对该区域建立实体模型,分析应力集中情况。计算结果表明钢箱梁结构整体受力状态良好,绝大部分区域应力数值均小于设计允许值;箱梁标准段和梁端压重区受力均满足规范要求;锚拉板局部应力集中现象明显(控制应力采用屈服应力),对应力集中位置须确保焊接后打磨匀顺并锤击以减少应力集中。

In this paper,considering the construction characteristics of the main bridge,the first system stress envelope in each stage of the main girder structure,and the second system stress were calculated respectively by using the beam element and the shell element.The internal and external plates of the steel box girder of the main bridge have complex force,so the local models of the standard section and the beam end compression section were established respectively for stress analysis.The steel anchor plate in cable beam end anchorage zone has concentrate force,so a solid model was established to analyze the stress concentration.The calculation results showed that the overall stress state of the steel box girder structure was good,and most of the stress values were less than the design allowable values.The stress of the standard section and the beam end compression section of the box girder all met the code requirements.Local stress concentration of anchor plate was obvious(yield stress was used to control the stress),so the stress concentration area should be polished evenly and hammered after welding to reduce the stress concentration.