摘要：
装配式公路钢桥在战时抢修、抗震救灾中桥梁修复与加固等应急工程中发挥了重要作用,但现有装配式公路钢桥最大理论跨越能力只有69m,导致部分交通要道的大跨度桥梁短时期无法修复,造成了巨大的经济效益和社会效益损失.为满足大跨度桥梁应急抢修的要求,以单跨90 m装配式公路钢桥为研究对象,提出采用抗弯和抗扭性能较好的矩形钢管截面作为桁架构件的主要截面以提高结构的跨越能力,在继承原有研究成果的基础上设计了“321”型、“200”型矩形钢管桁架方案,创新性地设计了“600”型矩形钢管桁架方案和三角形桁架方案.在有限元建模分析的基础上,详细分析了4种设计结构方案在移动荷载作用下的最大位移、组合应力、用钢量及1阶稳定屈曲系数这4个关键指标各自的优劣.为了方便桥梁设计方案的比选,以桥梁设计的基本目标作为评价设计方案的影响因素,利用模糊数学和层次分析法分解评判指标体系,建立了运用二级模糊综合评价决策方法进行设计方案优选比较的指标体系和方法.最后,结合单跨90 m装配式公路钢桥的4种设计方案,给出了模糊层次分析评价和设计方案优选的具体过程.研究结果表明:“600”型矩形钢管桁架方案所对应的判断结果矩阵中的元素值最大,说明该设计方案在力学性能、经济合理性、技术可行性、施工方便性等方面优势明显,为4个设计方案中的最优方案.研究成果可为后续大跨装配式公路钢桥的研制方案提供设计思路和技术参考.%Fabricated highway steel bridge plays an important role in the emergency projects of bridge repair and reinforcement in wartime rush repair and earthquake relief.But the maximum theoretical spanning capacity of existing fabricated highway steel bridge is only 69 m,which leads to the situation that large-span bridges of some major communication lines can not be repaired in a short period and results in huge economic and social benefits losses.To meet the emergency repair requirements of large-span bridge,a fabricated highway steel bridge with single span of 90 m was investigated.In order to improve spanning capacity of the structure,rectangular steel tube section with good flexural behavior and torsional property was adopted as the main section of the truss members.On the basis of the former research results,the “321” and “200” type rectangular steel tube truss schemes were designed,and then “600” rectangular steel tube truss scheme and the triangular truss scheme were innovatively designed.Based on finite element analysis,respective advantages and disadvantages of four key indexes,such as the maximum displacement,combination stress,amount of steel and the first order stable buckling coefficient under moving load of the four design schemes were analyzed in detail.In order to facilitate the comparison and selection of bridge design schemes,index systems and methods were established by using twolevel fuzzy comprehensive appraisal method to select the optimal design scheme,which took the fundamental objective of bridge design as influence factor to evaluate design scheme and used fuzzy mathematics and analytic hierarchy process decomposition to judge index system.Finally,combined with four design schemes of fabricated highway steel bridge with single span of 90 m,the concrete process of fuzzy analytic hierarchy process (AHP) evaluation and design scheme optimum selection was given.The results show that element value of “600” rectangular steel truss scheme'corresponding judgment result matrix is maximal,which means that this scheme has obvious advantages in mechanical performance,economical rationality,technical feasibility and construction convenience,so “600” rectangular steel truss scheme is the optimal among the four design schemes.The research results provide some scheme design ideas and technical reference for subsequent development scheme of large-span fabricated highway steel bridge.5 tabs,10 figs,22 refs.
