南沙大桥东涌互通主线二桥模架悬浇跨线施工技术

南沙大桥东涌互通主线二桥为一联五跨连续刚构桥,下穿、上跨多条既有线。该桥主梁采用节段悬臂浇筑工艺施工,其22至23号墩上跨既有C匝道,施工净空仅29 cm。为在不影响C匝道运营的前提下进行跨线施工,提出22至23号墩采用模架结构进行悬浇跨线施工。模架结构由钢壳和桁架两部分组成,其中,钢壳既作为施工阶段混凝土浇筑用模板,又作为混凝土箱梁结构的一部分,还兼做跨线施工防护棚。施工时,22号墩广州侧、23号墩东莞侧梁段采用挂篮进行节段悬浇施工;22号墩与23号墩间梁段采用模架结构进行节段悬浇施工,待跨中合龙段施工后,拆除墩身两侧的临时支撑、挂篮和桁架,完成跨线施工。

Construction Technique of Using Formwork for Cantilever Casting of No.2 Bridge Crossing Existing Railways on Tung Chung Interchange Section of Nansha Bridge Project

The No.2 Bridge on Tung Chung Interchange Section of Nansha Bridge project is a continuous rigid-frame bridge that incorporates five spans in a unit.The bridge goes below and overpasses multiple railways,leading to the adoption of a segmental cantilever casting of the superstructure.The span between pier 22 and 23 crosses the existing C ramp,with a construction clearance merely 29 cm.In order to carry out casting without disruption to the normal operation of C ramp,an overhead cantilever casting method of using formwork structure was proposed for this part.The formwork structure consists of steel shells and trusses,the steel shells have multiple purposes,which can be used as the formwork for concrete casting,will be parts of the finished concrete box beams,and also act as protection roof for the overhead construction.During the construction,the beams on the Guangzhou side of pier 22 and those on the Dongguan side of pier 23 were cast using form travelers.The beams between pier 22 and 23 were cast using formwork structure.After the installation of the midspan closure sections,the temporary supports attached to the pier shafts,form travelers and trusses were dismantled to finish railway-crossing construction.