杆端缩尺钢桁架桥梁结构静力计算与优化分析

Static Calculation and Optimization Analysis of Steel Truss Bridge Structures Containing Members with Section-Shrunk Ends

以某下承式铁路钢桁架简支梁桥的单榀Warren桁架为研究对象,对杆端缩尺钢桁架桥梁结构及其端部缩尺压杆进行有限元分析和用钢量优化,重点研究杆端缩尺参数对杆件内力、截面应力、结构刚度、结构弹性稳定、压杆极限承载力、最小用钢量等的影响。结果表明:杆件截面高度缩尺是最理想的杆端缩尺方案;随着缩尺幅度的增大,桁架结构的杆件轴力变化很小,但杆端次弯矩和剪力显著减小,且结构竖向刚度和弹性稳定性有所降低。通过适当提高缩尺段的钢材强度等级,端部缩尺压杆的极限承载力将不低于未缩尺压杆,并可在满足结构强度、刚度及稳定性要求的前提下,进一步通过杆件截面优化,得到比未缩尺设计更小的结构用钢量。

Taking a simply supported plane Warren truss of a through steel truss bridge as the research object,finite element analysis and steel weight optimization of steel truss bridge structures containing members with section-shrunk ends have been conducted.The influences of section-shrinking parameters on the indexes including member internal force,sectional stress,structural stiffness,elastic stability of structure,ultimate bearing capacity of compression member as well as minimum steel weight have been thoroughly studied.The results show that height-shrinking is the best choice for the section-shrinking design of member ends.As the section-shrinking is aggravated,the axial forces of members are very insignificantly enhanced and the secondary moments at member ends and member shears decrease remarkably,while the vertical stiffness and the elastic stability of the structure are slightly weakened.With the steel strength grade of section-shrunk segments having been properly improved,the ultimate bearing capacities of the axially compressed section-shrunk members are as high as those of uniform members,and a smaller steel weight can be obtained after the optimization of member cross-section,on the premise that the requirements of strength,stiffness and stability of the structure are satisfied.