文档介绍：华中科技大学
硕士学位论文
全预应力梁预应力损失的动力检测研究
姓名:李瑞鸽
申请学位级别:硕士
专业:结构工程
指导教师:张耀庭
20051106
摘要
预应力混凝土结构在使用过程中由于混凝土压缩收缩徐变钢筋的应力松
弛等因素会导致预应力筋的预应力损失预应力筋中现存的预应力及实际受力状况与
结构的工作状态密切相关所以预应力损失的检测是预应力结构健康检测和监测的重
要内容本文将从结构的动力性能出发通过结构的模态参数变化检测预应力筋的预
应力损失重点探讨无粘结全预应力梁的频率与预应力损失之间的关系
本文中制作了根无粘结预应力混凝土梁和根有粘结预应力混凝土梁对预应
力梁分级施加预应力分别测试在各级预应力状态下试验梁的前阶频率分析预应力
变化和频率变化之间的关系用以模拟预应力损失引起的频率变化试验结果表明
随着预应力的增加梁的频率不断上升当预应力增加到一定程度时梁的频率稍有
下降
论文中按照梁式压杆两端承受压力的动力模型建立了预应力混凝土梁的有限元计
算模型进行了试验梁的频率和振型的计算计算结果显示频率计算值随着梁中预
应力的增加而不断减小这一结论与试验结果相反造成这种结果的主要原因一是
没有考虑到混凝土是一种非均质材料在其凝结硬化过程中已经存在一些初始微裂缝
在预压应力作用下微裂缝闭合致使梁的整体刚度增加梁的频率上升另外一个因
素是由于一根钢筋在受拉时会随着拉力的增加频率升高即预应力筋中拉力的存在增
加了梁的整体刚度论文从这两方面入手对有限元计算模型进行了修正
本文推导了模态参数频率和振型对张拉力变化的敏感系数计算公式利用修
正过的动力有限元模型计算出模态参数对张拉力的灵敏度值用计算得到的灵敏度值
和试验得到的频率变化量预测张拉力的变化效果良好
关键词全预应力梁预应力混凝土预应力损失敏感性频率振型
II
Abstract
It is known that the loss of the prestress force in tendons occurs due to elastic shortening,
creep and shrinkage of concrete, steel relaxation, etc. in the condition of service of
prestressed concrete. Existing prestress force and the actual stress in tendons have close
connection with the active state of prestressed concrete structure, so the detection of
prestress loss is the important part of the health monitoring and detection of prestressed
concrete structure . The loss of prestress force is pre-estimated by the change of modal
parameter from dynamic nature of construction in this relations between the
frequency and prestress losse of unbonded prestressed concrete beam will be researched
chiefly in this paper.
Tow unbonded prestressed concrete beams and three bonded prestressed concrete beams
were made. Prestress force was applied to these beams in grades, then their first four steps
frequencies in every grade prestress force were measured. And relation of change between
prestress force and frequencies which are used to analog the prestess loss is analysed in this
paper. The test results indicate that the frequencies of th