宽幅钢箱梁大跨高位顶推施工关键技术

Key Construction Techniques for Long-Span and High-Position Incremental Launching of Wide Steel Box Girder

桃花峪黄河大桥主桥为(160+406+160)m双塔三跨自锚式悬索桥,主梁为宽幅钢箱梁(梁宽39m)。钢箱梁采用单向多点同步顶推(拖拉)施工,临时墩最大跨度82m、自由高度69m,钢箱梁顶推距离685.75m。针对临时墩跨度大、自由高度高的难点,采取临时墩群桩变刚度转换,临时墩滑道设置向后初始偏心,临时墩间设置预张拉索,拼装平台长短滑道结合设计等方式,提高施工结构承载力。针对钢箱梁远距离顶推线形和梁轴线控制需求,合理设置钢箱梁节段拼装、顶推以及合龙全过程的三向调整装置。研发低摩擦系数摩擦副、优化连续顶推(拖拉)控制系统及顶推设备同步控制精度,将顶推不平衡水平力控制在竖向力的5%以下。钢箱梁按顶推流程施工,南北两合龙口依次实现精确合龙。

The main bridge of Taohuayu Huanghe River Bridge is a two-tower self-anchored suspension bridge with three spans of 160, 406 and 160 m. The main girder is the wide steel box girder, with a width of 39 m. The steel box girder was constructed by the mono-directional and multi-point synchronized incremental launching (pulling and dragging). The maximum span length between temporary piers is 82 m, the free height of the temporary piers is 69 m, and the pushing distance of the steel box girder covers 685.75 m. The great free height of the temporary piers and the long distance between temporary piers make the construction quite challenging. In this light, a series of measures were taken to improve the load bearing capacity of the structure, like transferring the rigidity of grouped piles of the temporary piers, setting backward initial eccentricity on the sliding rails of temporary piers, setting stays for pre-tensioning among temporary piers, and properly arranging the long and short sliding rails on the assembly platform. Considering the long-distance pushing geometry of steel box girder and the control demands of the girder axle, the three-dimensional adjusting devices for the whole process of the steel box girder sections assembling, pushing and closing were installed. The friction sets with low friction factor was prepared, the control system for the continuous incremental launching (pushing and dragging) was optimized, and the accuracy of synchronized control of the incremental launching equipment was improved, to allow the imbalanced horizontal force in the incremental launching process to be less than 5% of the vertical force. The steel box girder was constructed following the workflow, and the south and north closure gaps were accurately closed one by one.