铁路整体PC箱形梁的徐变效应分析

研究目的:混凝土的徐变对预应力混凝土结构的影响不容忽视。在进行结构分析时,不同的计算模式,计算的内力和变形计算结果也不一样,其中混凝土徐变引起的预应力损失对于结构内力及变形的影响尚有待进一步探索。研究方法:文中结合铁路桥梁设计规范,采用MIDAS/Civil结构分析软件,对双线铁路整体PC箱梁在3种计算模式下,进行施工中预应力的张拉、落梁以及二期恒载作用阶段的受力和变形分析,探讨了徐变引起的预应力损失对结构的影响。研究结论:对简支结构而言,混凝土徐变不会产生次内力,但会使应力重新分布,考虑徐变引起的预应力损失将使梁体的内力减小;梁体在张拉力作用下产生上拱变形,并随时间推移而缓慢发展,二期恒载的作用将有效减小上拱挠度,梁体的徐变变形占总变形的50%,徐变引起的的变形对梁体对结构下挠不利,而对于上拱度的控制是有利的。

Creep Effect Analysis of the Whole PC Box Girder for Railway Bridge

Research purposes:Creep of concrete has significant influence for prestressed concrete structures.During structural analysis,different models of analysis cause different results of internal force and deformation. The influence of lose of prestress which caused by creep of concrete to the internal force and deformation of structure need further study.Research methods: Combining with the design code of railway bridges,internal force and deformation of a double lines railway bridge with PC box beam are analyzed at the stages of pretensioning,beam erecting and secondary dead load's acting under three analysis models using MIDAS/Civil program.The influence of lose of prestress caused by creep of concrete to structure is researched.Research conclusions: Creep of concrete cannot caused secondary internal force for a simple supported beam,but can cause stress redistribution. The internal force of beam is reduced when lose of prestress caused by creep is concerned.The up-deformation caused by prestress is developing slowly according to time passing.The action of secondary dead load reduce up-deformation significantly.The deformation caused by creep is nearly 50% of total deformation,which has disadvantage for down-deformation of structure but advantage for controlling of up-deformation.