10 徐变效应分析.ppt

混凝土桥结构理论
向天宇
西南交通大学桥梁工程系
Tel:**********
E-Mail: ******@.
第十一章混凝土结构的收缩徐变效应分析
1、混凝土收缩徐变基本概念
2、古典流变理论
3、CEB78模型与CEB90模型
4、徐变效应分析
5、结构时变效应分析的有限元方法
肖汝诚,桥梁结构分析及程序系统,人民交通出版社。
周履,收缩徐变,铁道出版社
1、混凝土收缩徐变基本概念
收缩与徐变是混凝土固有的一种时变物理和力学行为,这一特性会导致混凝土结构变形不断增大以及产生较大的内力重分布,严重时,会危及到结构安全。
1、混凝土收缩徐变基本概念
帕劳共和国于1978年修建的科罗·巴岛桥为一跨中带绞的72m+241m+72m三跨预应力混凝土连续刚构桥梁。到1990年,。1996年对该桥进行了加固,加固后3个月桥梁垮塌
1963年建成的美国弗吉尼亚州的Randolph Tucker高中体育馆,×,1970年屋盖垮塌。事故原因调查结论是“设计对混凝土收缩徐变效应与几何非线性效应的共同作用考虑不足导致结构失稳破坏”
1、混凝土收缩徐变基本概念——科罗巴岛桥
The bridge was designed to meet the need for a link between the two major islands of Palau, Koror and Babelthuap.
1、混凝土收缩徐变基本概念——科罗巴岛桥
1、混凝土收缩徐变基本概念——科罗巴岛桥
Each half of the bridge had been built as balanced but unsymmetric cantilevers, working away from the main pier, until the back span reached the end pier. This span was then filled with ballast to provide moment reaction pletion of the cantilevers.
1、混凝土收缩徐变基本概念——科罗巴岛桥
When it pleted in 1977, its main span of 241 m(791 ft) set the world record for segmental prestressed concrete box girders.
During the 18 years after pletion, the cantilevers deflected due to creep, shrinkage and prestress loss. By 1990 the sag of the centre line had reached , affecting the appearance of the bridge, causing fort to road users, and damage to the wearing surface.
1、混凝土收缩徐变基本概念——科罗巴岛桥
The Palauan missioned two teams of experts to assess the safety of the structure and its ability to continue to carry the design loads in the future. Louis Berger International (USA) and the Japan International Cooperation Agency both concluded that the bridge was safe and would remain so, but the deflection could be expected to increase further in the future (by another over the next 100 years).
As part of the assessment of the bridge a loaded truck weighing 125kN was driven onto the tip of each cantilever to determine its stiffness. The measured deflection was mm, which corresponds t