底部开口悬挂式单轨交通轨道梁扭转性能的计算与分析

Calculation and Analysis of Bottom-opening Suspended Monorail Transit Track Beam Torsional Performance

目的:在国内外对底部开口悬挂式单轨线路的研究中,尚缺少针对轨道梁扭转性能的研究及对曲线轨道梁竖向荷载作用下截面变形的影响分析,需对单轨线路轨道梁的扭转性能进行深入分析。方法:在结合我国悬挂式单轨和日本单轨设计经验的基础上,介绍了悬挂式单轨PC(预应力混凝土)轨道梁的结构,对结构梁所承受的竖向列车荷载进行分析。阐述了传统符拉索夫开口薄壁梁扭转理论存在的问题,推导了考虑跨中截面剪切应变情况下轨道梁约束扭转时的初参数解。结合有限元软件建立了曲线梁模型,对不同曲线半径及顶板厚度取值时竖向荷载作用跨中截面的竖向位移及扭矩变化情况进行了分析。在跨中截面处施加集中扭矩,对轨道梁跨中右侧区段各截面的受力情况进行分析,并将理论计算值与模型模拟值进行对比。结果及结论:两端固定约束下底部开口箱型PC轨道梁在跨中处承受集中扭矩时,不应忽略其剪切变形,该类轨道梁设计时应考虑剪切应变的影响;加大曲线轨道梁顶板厚度,可提高梁截面的整体抗扭性能;在竖向静活载作用下,跨中截面处的扭转角随着曲线半径的减小而增大。

Objective:In the research on bottom-opening suspended monorail lines in China and abroad,there is a lack of studies on track beam torsional performance and analysis of curved track beam profile deformation under vertical loads.It is necessary to conduct an in-depth analysis of monorail line track beam torsional performance.Method:Based on the design experiences of suspended monorails in China and monorails in Japan,the structure of suspended monorail PC(pre-stressed concrete)track beam is introduced,and the vertical train loads on structural beams is analyzed.The problems existing in the conventional Vlasov thin-walled beam theory are discussed,and the primary parametric solution for track beam restrained torsion considering the shear strain of the mid-span cross-section is derived.A curved beam model is established using finite element software to analyze the vertical displacement and torque variation at the mid-span cross-section caused by vertical load action when taking values of different curve radius and top plate thickness.Concentrated torsion is applied at the mid-span cross-section,and the stress distribution of various sections in the mid-span right segment of the track beam is analyzed,comparing theoretical calculation and model simulation values.Result&Conclusion:For bottom-opening box-shaped PC track beams with fixed constraints at both ends,the shear deformation should not be neglected when subjected to concentrated torsion at the mid-span cross-section.The influence of shear strain should be considered in the design of such track beams.Increasing the top plate thickness of curved track beams can enhance the overall torsional resistance performance of the beam cross-section.Under vertical static live loads,the torsional angle at the mid-span cross-section increases as the curve radius decreases.