PC箱梁短线法节段预制施工技术

Construction Techniques for PC Box Girder Prefabricated by Short-Line Match Casting Method

郑州桃花峪黄河大桥北引桥为3×(6×50)m+4×(50+4×51+50)m等高预应力混凝土连续梁桥,箱梁采用短线法节段预制、架桥机整孔拼装施工。箱梁节段自每跨中间向两端依次匹配预制,先浇筑完成节段作为相邻待浇节段的匹配段,匹配段采用底模台车多向精确定位。预制施工中,模板系统主要由固定端模及其钢支架、侧模及其钢支架、底模及底模台车、内模及滑车等组成;箱梁节段钢筋在钢筋绑扎台座成型,采用多点吊放入模并准确定位固定;箱梁C55混凝土集中拌制,用罐车运至制梁台座处,采用汽车泵浇筑;箱梁节段预制完成后存梁不少于3个月;箱梁横向预应力在预制场内张拉,纵向预应力在桥上施工;控制箱梁预制节段的中线、垂直度、水平度等线形满足规范要求。

The north approach of the Taohuayu Huanghe River Bridge in Zhengzhou is a constant-height prestressed concrete continuous beam bridge with span arrangement of 3 ×（6 × 50） m＋ 4× （50＋4 M 51＋50） m. The box beam was prefabricated by short-line match casting method and constructed a whole span a time using the gantry crane. The box beam segments were matched for prefabrication in sequence from the center of the span towards the two ends. The already-finished segments can be the matching segments in the casting of the adjacent segments. The matching segments are accurately positioned by using bottom formwork trolley from different directions. In the prefabrication, the formwork system is mainly made of fixed end formwork and its steel frame, side formwork and its steel frame, bottom formwork and trolley, inner formwork and pulleys. The reinforcing bars took shape in the binding pedestal, hoisted and lowered to the formwork via multi- ple points and accurately positioned. The C55 concrete for the box girder was mixed in a batching plant, transported to the casting pedestal by tank car and cast by truck pumps. The completed pre- fabricated box girder segments should be stored over three months. The transverse prestressing in the box girder was tensioned in the prefabrication yard and the longitudinal prestressing was tensioned on the bridge. The central line, verticality and levelness of the prefabricated segments should be controlled to meet the code requirements.