劲性骨架拱桥主拱圈混凝土四工作面浇筑法

Four-working-platform pouring method for main arch ring concrete of rigid skeleton arch bridge

为研究受力合理、施工方便、经济性好的劲性骨架拱桥主拱圈混凝土浇筑工作面设置方法,以南盘江特大桥为对象,分析了从两拱脚对称浇筑第1环混凝土在劲性拱骨架上产生的瞬时应力变化过程,做出了劲性骨架主要控制截面的应力过程线,提出了在全拱纵向对称设置4个工作面的主拱圈混凝土浇筑方法,并将工作面分别设置在拱脚截面和控制性应力过程线峰值处,使半跨内2个工作面上混凝土在劲性骨架中产生的应力增量异号,以抵消部分应力;通过分段拟合绝对控制应力过程线上升段和下降段的连续函数,合理调整了混凝土的浇筑长度和顺序,降低了劲性骨架的瞬时应力和变形;讨论了四工作面浇筑法的施工操作性和经济性,并采用该方法分析了南盘江特大桥主拱圈第1环混凝土浇筑过程中劲性骨架的应力和变形。研究结果表明:拱脚管内混凝土应力过程线为控制性应力过程线且为单波曲线;提出的先跨内、后拱脚,并按拟合函数计算的长度进行南盘江特大桥混凝土浇筑的四工作面法是合理的,该桥劲性骨架最大瞬时拉、压应力分别降至0.4和23.5 MPa,被较好地控制在材料强度范围内,拱顶无上挠,最大瞬时下挠和环末下挠分别为192、82 mm,拱轴线不发生反复变形;四工作面浇筑法所需设备和人员较少,具有良好的操作性和经济性,适合于劲性骨架拱桥主拱圈混凝土浇筑,可为同类桥梁采用。

To investigate a method of setting working platforms during the concrete pouring for the main arch ring of a rigid skeleton under a reasonable stress and with a convenient and economical construction and taking the Nanpanjiang Super Long Span Bridge as an object, the transient stress variation process of rigid skeleton caused by the first ring concrete symmetrically poured from the two arch springs was analyzed. The stress process curves of the main control section of rigid skeleton were obtained. A concrete pouring method for the main arch ring was proposed with four working platforms arranged symmetrically along the longitudinal arch, and the working platforms were set at the arch spring section and the peak of control stress process curve, such that the stress increments on the rigid skeleton generated by the cocrete of two working platforms within the half span had different signs to offest part of the stress. By fitting the continuous functions of the ascending and descending sections of absolute control stress process curve, the pouring length and sequence of concrete was reasonably adjusted to reduce the transient stress and deformation of rigid skeleton. The construction operability and economy of the four-working-platform method were discussed, and the stress and deformation of rigid skeleton during the concrete pouring process for the first ring of main arch ring of Nanpanjiang Super Long Span Bridge were analyzed. Research result shows that the stress process curve of concrete filled in the arch spring tube represents a control stress and single wave curve. The proposed four-working-platform method with the order of first along the span, then in arch spring and with the length calculated by the fitting function is reasonable for the concrete pouring of Nanpanjiang Super Long Span Bridge. The maximum transient tensile and compressive stresses of rigid skeleton reduce to 0.4 and 23.5 MPa, respectively, which are well controlled within the range of material strength. The vault has no upward deflection, the maximum transient deflection and eternal ring deflection are 192 and 82 mm, respectively, and the arch axis does not deform repeatedly. The four-working-platform pouring method requires less equipment and personnel, is economical, and has good operability. It is suitable for the concrete pouring for the main arch ring of rigid skeleton arch bridges, and can be used for similar bridges. 2 tabs, 7 figs, 30 refs.