孟加拉帕德玛大桥半预制半现浇混凝土边护栏施工技术

Precast and Cast-in-Situ Combined Construction Technique for Concrete Edge Parapets of Padma Bridge in Bangladesh

孟加拉帕德玛大桥公路桥面边护栏采用钢筋混凝土墙式护栏,总长约18 km,高度达1.8 m,护栏外侧设置装饰槽,护栏底部伸至桥面板顶面以下且截面尺寸小。对护栏全现浇和全预制2种施工方案进行分析,提出一种半预制半现浇组合施工方案。预制现浇分界线以护栏顶面中间位置开始延伸至与桥面翼缘顶面接触位置,外侧采用预制,预制节段长1.5 m;内侧采用现浇,现浇节段长度一般为9 m,根据灯柱的布置,设置6 m或7.5 m的调节分段长度,实现模块化施工。在预制场采用预制台座、模板和平躺预制方式预制边护栏的外侧部分,涂刷缓凝剂对预制现浇的湿接缝处进行冲洗凿毛,并预留锚固钢筋,利用预埋的吊装吊耳和支撑角钢在桥上安装预制的外侧部分后现浇内侧部分,通过锚固钢筋将边护栏与桥面板结合在一起。采用该施工方案,每月可预制1300片护栏,现浇段每月可施工3600 m,5个月内完成护栏现浇,护栏施工完成后的整体混凝土外观质量优良。

Measured 18 km in total length and 1.8 m in depth,the reinforced concrete edge parapets of the roadway deck of the Padma Bridge feature the decorative grooves on exterior facades,and the parapets are thickest in the center,gradually go thinner upwards and downwards,and extend downwards with a portion stretching below the roadway deck.Based on the analysis of all-precast and all cast-in-situ options,a precast and cast-in-situ combined construction technique was proposed.Split the parapets into two parts along the bridge longitudinal axis,the interior part connecting the deck was cast in situ in 9 m-long segments and the exterior part was precast off site in 1.5 m-long segments,while 6 m-and 7 m-long adjustment segments were placed to coincide with the lamp posts,to achieve the modularized construction.The segments of the exterior part of the parapets were precast in a lying manner with the casting beds and formwork in the fabrication yard,after coated with retarder,the stitches containing protruding reinforced bars to create continuity were cleared and roughened.With the assistance of the embedded lifting lugs and supporting angle steels,the prefabricated segments were installed,afterwards,the casting of the interior part began.The parapets were fixed with the deck panels via the reserved reinforced bars.A number of 1300 segments of the parapets were prefabricated per month,and 3600 m-long segments were cast per month.The casting of the interior part of the parapets was finished in 5 months,and the visual quality of the concrete components was sound after the parapet construction.