连续多跨矮塔斜拉桥力学性能分析

以开封黄河二桥主桥为研究对象,采用有限元程序Midas/civil对该桥进行了力学性能分析.计算结果表明:由于该桥塔高与跨径之比较大,斜拉索承担较多的竖向荷载,能有效降低主梁支点截面的高度和内力;主梁的内力与变形表现为多跨连续梁的受力特点,主梁基本全截面受压,轴力分布较为均匀,在桥塔根部支点处出现较大正弯矩,跨中出现负弯矩;主梁刚度较大,整体变形以向上为主,变形量较小;主塔只起到拉索转向块的作用,纵向受力较小,故各塔顶纵桥向位移较小,在中等跨径范围内,可采用多跨矮塔斜拉桥方案解决普通多跨斜拉桥的刚度问题;每根塔柱两侧拉索的拉力由内向外依次小幅增大,总体分布均匀,边跨索索力最大,活载作用引起的拉索应力增幅较小;桥梁结构在非对称活载作用下的受力更为不利;各构件控制截面应力及变形均在桥梁设计规范规定范围内,且具有足够的安全储备,桥梁结构受力合理.

Mechanics Properties Analysis for Continuous Multi-span Low Pylon Cable-stayed Bridge

The 2nd Yellow River bridge in Kaifeng is a double plane prestressed concrete cable-stayed bridge with 7 low pylons and 8 spans.The bridge was taken as the object of study and mechanics properties analysis of it had been made by adopting finite element program Midas/civil.The results indicate that stay cables undertake more vertical loads because of the bigger ratio between height of king pylons and spans of girder,so the height and internal force of the girder sections at supporting points can be decreased effectively;the internal forces and deformations of the girder display an characteristic as well as multi-span continuous beams,the whole sections of girder are all under compressive stress basically,axis force distribution is uniform,the positive bending moment appears at the supporting points of girder and it is larger than the hogging moment at the mid-spans;the stiffness of girder is large,because the deformation of girder gives priority to the smaller upwards vertical deformation;the king pylons only serve as a steering column for stay cables and force in longitudinal direction is smaller,the displacements at the top of pylons in the longitudinal direction of bridge is so small that in scale of medium spans,the scheme of low pylons cable-stayed bridge can sovle the problem of stiffness of multi-span cable-stayed bridge;The tension forces of cables at both sides of each pylon increase gradually from inside to outside,the force of cables of side-span is largest,and the growth of cables stress under live loads is very small;the bridge under asymmetric loads is disadvantageous,the stress and deformation of control section of each members are all in the range of the standard of criterion and have great safety storage,the structure of bridge is reasonable under loads.