赤石大桥主桥超高墩桥塔结构优化及试验研究

赤石大桥主桥为(165+3×380+165)m四塔双索面斜拉桥,桥塔采用空间双曲线塔墩+A形塔柱的超高墩桥塔,塔底至桥面高度达182.2m。为确定该桥合理的结构体系和桥塔参数并验证超高墩桥塔结构的适用性,采用MIDASCivil软件建立全桥有限元模型,分析不同结构体系和不同塔柱分肢宽度、塔墩分肢高度下的结构响应,并制作1∶20塔墩节段模型进行静载试验,研究桥塔的受力性能。结果表明:赤石大桥主桥采用中塔处塔梁墩固结、边塔处塔墩固结并在墩顶设置支座的结构体系,塔墩分肢高度取60m,塔柱分肢宽度取16m时,受力状态最优;塔墩竖向应力沿高度方向呈“中间大、两端小”分布;塔墩开裂荷载为1.41倍设计荷载,结构满足承载能力要求;桥面附近B横梁处首先出现裂缝,建议增加预应力改善其受力状态。

Structural Optimization and Experimental Study of Superhigh Pier Pylon for Main Bridge of Chishi Bridge

The main bridge of Chishi Bridge is a cable-stayed bridge with spans of (165+3×380+165) m, which is constituted by 4 pylons and two cable planes. The superhigh pylons with a distance of 182.2m between deck and ground are comprised of spatial hyperbolic pier curved pylon pier and A-shaped pylon columns. In order to determine a reasonable structural system of the bridge, to obtain the reasonable structural parameters of pylon and to verify the applicability of the superhigh pier pylon structure, we established a finite element model by MIDAS Civil software to analyze the structural responses under the conditions of different structural systems, different embranchment widths of pylon column and different embranchment heights of pier. Moreover, we built a sectional model of pier with scale of 1∶20 to perform static load test so as to study the mechanical properties of the pylon. The results reveal that the structural system of pylon-girder-pier consolidation at middle pylon, pylon-pier consolidation and installment of bearing at pier top at side pylon which is adopted in the main bridge of Chishi Bridge possesses optimum mechanical properties, in which the embranchment height of pier is 60 m and embranchment width of pylon column is 16 m. The vertical stress distributes in a mode of "high stress in the middle but low stresses at both ends" along the vertical direction of pylon pier, and the cracking load of the structure is 1.41 times the design load, meeting the bearing capacity requirements of pylons. The first crack appears at cross beam B, thus it is suggested to adopt prestress to improve the stress states.