韩江北桥主桥动力特性研究

Dynamic characteristics analysis of Hanjiang Northen Bridge

以韩江北桥主桥主跨钢管混凝土拱桥初步设计方案为对象,采用ANSYS有限元程序,考虑边跨对主跨的弹性约束作用,建立了该中承式钢管混凝土拱桥主跨的整体动力计算有限元模型,分3种工况(实桥模型;在实桥模型的拱肋间增设横向风撑;将实桥模型的端横梁的顶板、底板和腹板厚度增大1倍)计算了桥梁的振动特性。计算结果表明:实桥模型的拱肋面外刚度较小,在桥梁振动中首先出现拱肋的面外振动,且桥梁前10阶振型中有6阶为拱肋的面外振动;桥梁拱肋面外自振基频明显小于桥梁整体竖向自振基频,说明桥梁拱肋面外刚度与全桥竖向刚度相差较大;桥面系面外刚度相对较弱,桥梁前10阶振型中出现了扭转振动形式。增设横向风撑后,拱肋面外刚度明显增大,对该桥梁动力特性的影响较为明显;增大端横梁截面尺寸对该桥梁动力特性影响不大。计算结果为该桥梁的设计修改提供了参考。

Hanjiang Northen Bridge is a concrete filled steel tubular arch bridge in Chaozhou city of Guangdong province . Regarding its main span as the research object , we adopt ANSYS finite element program , consider the border span＇s elastic restricted function to the main span, a space finite element dynamic calculated model of the half - through concrete filled steel tubular arch bridge was established , then we divide into three operating modes in the text ： real bridge model ; adding transverse bracings between the arch ribs of the real bridge model ; increasing the thickness of transverse beam＇s top slab,bottom slab and web 1 times ; we analyse the dynamic characteristics of this bridge. The calculation result indicates that in the true bridge model the out - surface stiffness of the arch rib is small, the out - surface vibration of the arch rib appears first in bridge vibration and there are 6 steps of out - surface vibration in first 10 steps. The out - space basic frequency of arch rib is smaller obviously than the holistic vertical basic frequency. This shows that the difference between the out - surface stiffness of the arch rib and the vertical stiffness is great. The out - surface stiffness of the bridge deck is weak, the distorted vibration appears in the first 10 steps. Adding transverse bracings increases the out - surface stiffness of the arch rib, it influents the dynamic characteristics of the bridge greatly . Increasing the section size of the transverse beam influents the dynamic characteristics very little. The calculation result of this paper has already offered reference to improve the structural design of bridges.