跨采空区上承式120m简支钢桁梁的设计研究

Design of A 120 m Simple-Supported Steel Truss Girder over Goaf

贵金古高速公路杜家山特大桥主桥为跨径120 m的上承式简支钢桁梁,跨越煤矿采空区。综合考虑路线、桥面布置和结构受力等因素,决定主桁采用上承式普拉特式桁架,桁高12.5 m,标准节段长度12 m。桥面系采用混凝土与密集横梁结合体系。桥梁位于缓和曲线上,采用悬臂变宽解决桥面变宽问题,采用腹杆变高、上弦杆变高以及混凝土板变厚相结合的办法解决曲线超高变化的问题,避免了单一方法造成的施工难度过大或桥面恒载过大等问题。设计计算时,采用极限状态法指导设计,基于Midas/Civil建立有限元模型,计算结果表明,各项指标均满足公路钢结构桥梁规范要求。设计时引入BIM技术,对于提高设计质量大有帮助。

Dujiashan large-span bridge on the Guiyang-Jinsha-Gulin Expressway is a 120 m simple-supported steel truss deck girder structure over goaf.Considering the factors such as route,deck layout and structure stress,the main truss is designed to adopt the deck type of Pratt truss,with the truss height of 12.5 m and the standard segment length of 12 m.The bridge deck is a combination system of concrete and dense transverse beams.The bridge is located on the easing curve,so the cantilever widening is adopted to solve the problem of the bridge deck widening,and the combination of the web member’s height,the upper chord’s height and the concrete slab is adopted to solve the problem of the over-high variation of the curve,so as to avoid the problems of excessive construction difficulty or excessive dead load of the bridge deck caused by the single method.During design and calculation,the limit state method is used to guide the design,and the finite element model is established based on Midas/Civil.The calculation results show that all the indicators meet the requirements of the highway steel structure bridge specification.The introduction of BIM during design is a great help in providing design quality.