移动模架在超宽鱼腹形现浇箱梁施工中的研究与应用

Research and Application for Movable Formwork During Super Wide Fish-bellied Cast-in-situ Box Girder Construction

武四湖大桥是国内首个采用移动模架施工的鱼腹形现浇箱梁,单幅箱梁宽21.5m,混凝土浇筑最大荷载2400t,相较于以往移动模架施工,本套移动模架在设计、拼装、预压、混凝土浇筑等方面施工难度大。通过采用ANSYS有限元分析软件进行整体建模,在确保安全的前提下进行结构优化,减小其重荷比。并创新采用中支腿自动平衡控制技术、双折叠分级开合控制技术,研制出了一套适于宽幅、低墩、大荷载的上行式双折叠移动模架;在移动模架拼装过程中,采用纵移顶推拼装法,在桥跨下方无工作面的情况下,实现快速拼装。在移动模架预压过程中,采用多仓多区复合加载预压技术,精确模拟浇筑工况,取得各构件的变形量,为预拱度的设置提供理论依据。在混凝土浇筑过程中,针对桥梁宽度较大、空间效应明显的特点,采用空间线形控制技术和对称叠合浇筑法,实现对空间效应明显的超宽桥梁进行纵、横向线形的双向控制,以及避免了混凝土出现裂缝及接合面错台。

Wusihu Bridge is the first case of domestic application of fish-bellied cast-in-situ box girder with movable formwork. The single width of box girder reaches 21.5m. The load maximum of concrete casting is 2 400 tons. Design, assembling and preloading of this movable formwork as well as concrete casting have great difficulties compared to former movable formworks. Under the premise of ensuring safety, overall modeling with finite element analysis software ANSYS is used to optimize the structure and reduce the load ratio. Also an innovative middle-leg automatic balance control technology and a double- fold hierarchical opening-closing control technology are adopted to create a double-fold uplink movable framework suitable for broad width, low pier and heavy load. During assembling, without existing operation area under the bridge, longitudinal shift pushing method is adopted for rapid operation. During preloading, multi-cabin ＆ multi-zone combination preloading technology is adopted for simulation of casting conditions and acquisition of deflection providing theoretical basis for settings of camber. During concrete casting, on account of broad width and obvious space effect, space linear control technology and symmetrical-overlap casting method are adopted for realization of longitudinal ＆ transverse two-way linear control to avoid concrete crack and joint mismatch.