高速铁路无独立合龙段的T构桥主梁施工技术

Superstructure Erection Techniques for T-Frame High-Speed Railway Bridge Without Independent Closure Section

新建福厦铁路泉州湾跨海大桥为时速达350 km的高速铁路桥,其海上浅滩区部分引桥为15联(50+50)m T形刚构桥。主梁为单箱单室预应力混凝土箱梁,采用挂篮对称双悬臂浇筑施工,T构未设置独立合龙段,而是采用浇筑最后一节边跨直线现浇段的方式直接实现T构梁段合龙。主梁施工过程中,墩顶0号块(A0节段)采用三角托架法现浇施工,三角托架安装后进行预压,然后采用一次浇筑成型工艺浇筑节段混凝土;A1~A12悬臂节段采用全封闭式挂篮悬臂施工;在A13边跨直线现浇段施工时,对落地钢管支架法、边墩三角托架法、墩顶吊架法、挂篮悬臂浇筑法进行综合比选,最终选择挂篮悬臂浇筑法施工。A13边跨直线现浇段施工时,利用挂篮底平台作为其底模系统、挂篮外侧模板作为其外侧模板,采用3拼I14型钢对挂篮底纵梁进行支撑,在墩帽处垫石两侧用?20 mm精轧螺纹钢对挂篮进行对拉,增强了模板稳定性;通过平衡配重的设置及支座约束解除时机的控制,保证了A13节段施工质量。结构受力及线形均满足设计要求。

The Quanzhou Bay Sea-Crossing Bridge of the newly-built Fuzhou-Xiamen Railway allows trains to run through with a speed of 350 km/h.The approach bridge in the shallow offshore area is a T rigid-frame bridge with 15 continuous units,each containing two spans of 50 m.The superstructure of the T rigid-frame bridge consists of single-cell prestressed concrete box girders that were symmetrically cast in situ in balanced cantilever method using form travelers.During construction,no independent closure section was reserved,and the closure of the T-frame was achieved via the in-situ casting of the last straight side-span section.The section A0 over pier top was cast in place on the triangular brackets,the triangular brackets needed to be pre-loaded first after installation,then the section A0 were cast to take shape with a one-off concreting and forming technique.The sections A1-A12 were cast in situ using fully-closed form travelers.For the A13 section,namely the straight cast-in-situ section in the side span,four different casting methods were compared,including the utilization of at-grade steel-tube scaffolds,side-pier triangular brackets,pier-top lifting frames and form travelers,and the form travelers were finally chosen.The platform beneath the form travelers and the external formwork of the form travelers could be used as the bottom and side formwork,respectively.The stringers beneath the form travelers could be supported by threeⅠ14 section steels that were spliced together.The?20 mm finishing rolling rebars were installed and protruded out from the padding stones at the pier caps to tension the form travelers from two opposite directions to improve the stability of the formwork.The placement of counterweights and the release of the restriction to bearings were controlled,to ensure the construction quality of the section A13.The load bearing capacity and alignment of the structure could meet the design requirements.