The main bridge of the Qingshan Bridge in Nanning is a double-pylon hybrid girder cable-stayed bridge with the main span of 430 m.The pylons of the bridge are the reinforced concrete special-shaped arch pylons and the pylon columns were constructed,using the automatic hydraulic climb formwork.In the construction,5 temporary crossing bracings were arranged for a pylon along the height of the pylon columns.To effectively control the deformation and stresses of the pylons,4 schemes of the crossing bracings (3 types of the horizontal crossing bracings and 1 type of the cross bracings+diagonal bracings) were proposed.The software ANSYS was used to establish the spatial finite element model for the pylons,the whole construction processes of the pylons were simulated and the displacement and stresses of the crossing bracings and pylon columns were analyzed.The results of the analysis demonstrate that the transverse and vertical displacement of the scheme of the crossing bracings+diagonal bracings is the least,the stress levels are the lowest and with the scheme,the stresses and deformation of the pylons can be controlled most effectively.In that case,the scheme is selected.From the analysis of the influences of the lower cross bracings in the scheme on the displacement and the spatial force conditions of the py-lons,it is known that the compressive and tensile stresses of the pylon columns are respectively controlled within 10.0 MPa and 0.7 MPa.The maximum displacement of the pylons in the transverse direction of the bridge is 7.8 mm,the inclination is about 1/17 600 and the displacement and inclination can all satisfy the construction requirements.%南宁青山大桥主桥为主跨430 m的双塔混合梁斜拉桥,桥塔采用钢筋混凝土异型拱结构,塔柱采用全自动液压爬模施工,施工中沿塔柱高度方向布置了5道临时横撑.为有效控制施工过程中桥塔的变形和应力,提出4种(3种水平横撑和1种"横撑+斜撑")临时横撑方案,采用ANSYS软件建立桥塔的空间有限元模型,模拟桥塔施工全过程,分析临时横撑和塔柱的位移和应力.结果表明:"横撑+斜撑"方案的临时横撑横向和竖向位移最小,受到的应力水平最低,最能有效控制桥塔的应力和变形.因此,采用"横撑+斜撑"方案.分析该方案下横撑对桥塔的位移和空间受力影响可知:塔柱的压、拉应力分别控制在10.0 MPa和0.7 MPa内;桥塔横桥向最大位移为7.8 mm,倾斜度约为1/17 600,均满足施工要求.
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