攀枝花市新密地大桥主拱圈设计

Design of Main Arch Ring of New Midi Bridge in Panzhihua City

攀枝花市新密地大桥为上承式钢筋混凝土箱形拱桥,孔跨布置为(27.5+22.55+189.9+22.55+27.5)m,主拱圈为悬链线无铰拱,采用挂篮悬臂浇筑法施工。主拱圈净跨径182m、净矢高30.333m、净矢跨比1/6、拱轴系数1.988。拱圈截面为单箱双室,高3.5m、宽9.6m。主拱圈的拱顶预拱度设计值为0.36m,为净跨径的1/506。采用MIDAS Civil软件建模进行成桥弹性阶段主拱圈应力验算,结果表明,主拱圈各截面上缘和下缘的正应力均为压应力,关键截面最小压应力为0.97MPa,最大压应力为15.4MPa,无受力裂缝,有利于提高结构耐久性。

The New Midi Bridge in Panzhihua City is a reinforced concrete deck box arch bridge with span arrangement （27.5＋22.55＋189.9＋22.55＋27.5） m. The main arch ring of the bridge is the catenary hingeless arch and is constructed by the traveling carriage cantilever casting method. The net span length of the arch ring is 182 m, net rise is 30. 333 m, net rise-tospan ratio is 1/6 and the arch axis coefficient is 1. 988. The cross section of the arch ring is the double-cell single box that is 3.5 m high and 9.6 m wide. The designed value of the arch top precambering of the arch ring is 0. 36 m that accounts for 1/506 of the net span length. The software MIDAS Civil is used to establish the models and the checking calculation of the stress of the arch ring at the elastic stage of the completed bridge is implemented. The results of the calculation show that the normal stress of the upper and lower edges of the various cross sections of the arch ring is all the compressive stress. The minimum compressive stress of the critical section is 0.97 MPa while the maximum compressive stress is 15. 4 MPa. The cross sections have no loading cracks, which is good for improvement of the structural durability.