高阶振型对大跨度钢桁拱桥地震反应的影响

为探讨高阶振型对大跨度钢桁拱桥地震反应的影响,以某1~490 m上承式钢桁拱桥为研究对象,采用MIDAS Civil软件建立全桥有限元模型,基于振型分解反应谱法基本原理,通过动力分析与静力分析相结合的方法,提出了高阶振型对大跨度钢桁拱桥地震反应的分离方法,在此基础上分析了主控振型对大跨度钢桁拱桥主拱圈纵向地震反应的影响规律。结果表明:同一振型对主桁下弦杆的同一位置不同内力分量的影响程度不同。同一振型对主桁下弦杆不同区域的同一内力分量的影响程度不同。从主桁下弦杆整体内力分布看,各阶振型对下弦杆的轴力、弯矩影响规律较为接近,但对剪力的影响明显不同。对于轴力和弯矩,在L/8区域~拱脚区域内,高阶振型的影响显著。对于剪力,在跨中区域~L/4区域,高阶振型的影响显著,且多阶振型共同作用效果明显。

Influence of high-order modes on the seismic response of a long-span steel truss arch bridge

To study the effect of high-order modes on the seismic response of long-span steel truss arch bridges，a deck-type steel truss arch bridge with a span of 490 m was taken as the research object．By virtue of the software MIDAS Civil to build the finite element model of the whole bridge，based on the fundamental principle of mode analysis spectrum method，the separation method for the seismic response of the bridge with high-order modes was introduced by combinedly using the dynamic analysis and static analysis．On this basis，the influence of main control orders on the longitudinal seismic response of the main arch ring of the bridge was analyzed，and the seismic response mechanism was revealed．The results show that the influence of the same vibration mode on different internal force components at the same position of the chord bar under the main truss is different．The same vibration mode has different influence on the same internal force component in different areas of the chord under the main truss．Viewing the overall internal force distribution on the lower chord of the main truss，the influence of different modes on the axial force and bending moment on the lower chord is similar，but the influence on the shear force is obviously different．For the axial force and bending moment，in the region from L/8 to arch foot，the high-order vibration mode has a significant impact．For shear force,in the region from middle-span to L/4，the influence of high-order modes is significant，and the effect of multi-mode coaction is obvious．