矮塔斜拉桥分丝管索鞍区受力特征研究

Study of Mechanical Characteristics for Strand Deviating Saddle Zone of Extra-Dosed Cable-Stayed Bridge

为研究矮塔斜拉桥分丝管索鞍区混凝土应力的分布规律及其极限荷载,以京沪高铁津沪联络线特大桥主桥(主跨115m的三塔双索面矮塔斜拉桥)为背景,针对其索塔锚固区进行足尺节段模型试验,采用ANSYS软件建立索塔锚固区节段有限元模型,分析索塔锚固区混凝土的应力分布、极限荷载及易开裂区域。结果表明:索塔锚固区分丝管索鞍下方混凝土的横向劈裂应力、竖向压应力沿纵向、横向分布规律相似,均从桥塔中心线向两侧逐渐减小,呈抛物线形分布;索鞍下方混凝土应力分布比较均匀,结构处于弹性状态,受力满足要求;索塔锚固区的极限荷载为设计索力的1.56倍,有一定安全储备;索鞍下方混凝土易被拉裂,建议设计时适当加密该区域钢筋。

To investigate the stress distribution and ultimate load of the concrete in the saddle zone of the extra dosed cable stayed bridge, the main bridge of Tianjin Shanghai Link Line Bridge in Beijing Shanghai High Speed Railway is selected as the actual engineering background. The bridge is an extra dosed cable stayed bridge with a main span of 115 m and with three pylons, double cable planes. A full scale segmental model test for the anchorage zone in pylon of the bridge was carried out. Meanwhile, the segment finite element model for the anchorage zone was estab lished using the software ANSYS, the concrete stress distribution, ultimate load and concrete cracking prone area in the anchorage zone were analyzed. The results show that the distribution laws of the transverse splitting stress and vertical compressive stress of the concrete below the strand deviating saddle anchorage zone along the longitudinal and lateral direction are similar, both of which decrease gradually from the center line to the two sides of the pylon and exhibit the para bolic distribution. The stress distribution of the concrete below the saddle is relatively uniform and the structure is in the elastic state, which ensure the force condition meets the design require ments. The ultimate load of the anchorage zone in pylon is 1.56 times of the design cable force and has certain safety margin. The concrete below the saddle is easy to be tensile splitting, therefore, it is suggested that the reinforcement for the saddle should be properly densified in the design of the extra dosed cable-stayed bridge