中文摘要：

针对直埋热水供热管道弯管受力的复杂性,基于土弹簧模型建立了三维热-力耦合有限元模型,分析了直埋直角弯管应力的主要影响因素,给出了缩短弯臂长度的热-力耦合有限元模型。建模中管土相互作用考虑了介质的重力和覆土重力等的作用,弯头管段的边界条件施加在2个弯臂端头。结果表明,直埋弯管在温升作用下的峰值应力远大于内压作用下的峰值应力;直埋弯管的一次应力随管道壁厚、管道埋深的增加而降低,随内压、弯头曲率半径的增加而增加;直埋弯管的二次应力随管道壁厚的增加而降低,随内压、埋深、温升、弯头曲率半径、弯头端部位移的增加而增加;弯头截面竖向椭圆化对弯头是有利的,而横向椭圆化是有害的;地面荷载作用使弯头最大当量应力减小,对弯头起保护作用。该研究旨在为直埋管道的安全性分析提供帮助。

英文摘要：

Aiming at the complicated stress characteristics of bends in directly buried heating pipelines,a three-dimensional thermal-mechanical coupled finite element model was constructed in terms of soil spring model.The main affecting factors on stress distribution of directly buried bends were analyzed.A thermal-mechanical coupled finite element model for bend with reduced straight pipe lengths was given.The weights of thermal medium and covering soil were considered in the pipe-soil interaction of the model.The boundary conditions were exerted to the ends of two bend arms.The results indicate that buried elbows of bends bear peak stresses with considerably higher value due to temperature rise than due to internal pressure.The primary stress of buried bend decreases with the increasing pipe wall thickness and buried depth,while it increases with the increasing internal pressure and curvature radius.The secondary stress of buried bend decreases with the increasing pipe wall thickness,while it increases with the increasing internal pressure, buried depth,temperature rise,curvature radius and end displacements of bend arms.Vertical ovalization for pipe section is beneficial to the bend,buttransverse ovalization is harmful.The ground load reduces the maximum equivalent stress in buried bend.