月牙形多拱肋钢管混凝土桁架拱桥动力冲击系数研究

针对造型美观但结构形式特殊的月牙形多拱肋钢管混凝土桁架拱桥,应用考虑拉索侧向振动的车桥耦合振动分析方法,讨论了路面粗糙度、行车速度、结构阻尼取值对车辆轮压荷载、拱肋和主梁的挠度及拉索张力冲击系数的影响。结果表明:路面粗糙度对桥梁振动响应的影响显著,提高路面平整度可以降低桥梁冲击系数;行车对桥梁冲击系数的影响与结构振动卓越频率有关,提高车速并不意味振动冲击系数会增大;在相同的行车条件下,不同构件、不同截面的冲击系数有很大离散性,拱肋跨中截面的挠度冲击系数明显高于1/4跨中截面,主梁跨中截面的挠度冲击系数与1/4跨中截面的相差不大,端部的短吊杆张力冲击系数大于跨中的长吊杆;结构阻尼在经验范围内变动时,对冲击系数的影响不明显。

THEORETICAL STUDY ON THE IMPACT FACTOR OF CRESCENT-SHAPED MULTI-RIB CONCRETE FILLED STEEL TUBE TRUSS ARCH BRIDGES

Crescent-shaped multi-rib concrete filled steel tube truss arch bridges have attractive figures but complex structural types.The impact factors of arch rib,main girder deflection and cable tension were investigated in this paper.The reasons causing impact effect considered in this paper involves road surface roughness,vehicle speed,and the damping ratio of the structure.The following conclusions can be drawn according to analyzing results:(1)Impact factors of bridges will be reduced by smoothing road surface.(2)The effect of vehicle speed on impact factors is related with the primary modes inducing the response,and hence increasing vehicle speed may not increase impact factors.(3)The maximum impact factor is associated with the vehicle speed of 60 km/h.(4)Impact factors for different components and sections are quite different,although vehicle travels under the same condition.(5)Impact factors of arch rib deflection in mid-span are obviously larger than that in the 1/4 span.(6)For girders,the deflection impact factors between mid-span and 1/4 span are close.(7) Impact factors of tension in short cables at the end of the span are larger than that of long ones at the mid-span.(8) Damping ratio of structure does not affect impact factors significantly.