【作者】 张力；

【导师】 徐世烺； 李庆华；

【作者基本信息】 浙江大学 ， 结构工程， 2013， 硕士

【摘要】 混凝土造价便宜、原料分布广泛,在建筑工程领域有着广泛的应用。但混凝土是一种脆性材料,在受拉时容易产生裂缝,从而造成承载能力和耐久性的不足。UHTCCC(Ultra High Toughness Cementitious Composites)的多缝开裂性能和应变硬化特性使它具有良好的变形能力和承载能力,可以弥补普通混凝土脆性易开裂的缺陷。UHTCC的极限拉应变能够达到3%—7%,它开裂时呈多缝开裂模型,裂缝宽度可以控制在100μm以内甚至可以控制在40μm以下。但是UHTCC价格昂贵,这就限制了其在工程中的大规模应用。因此在结构构件关键部位使用UHTCC是一个比较合理的应对措施。早前用UHTCC替代钢筋混凝土梁受弯部分的UHTCC功能梯度梁(UHTCC-FGC梁)的静载实验研究和理论推导表明比起普通钢筋混凝土,UHTCC-FGC梁在开裂时呈多缝开裂状态,它变形能力和极限承载能力比普通混凝土更强。在国家自然科学基金项目(51008270)和教育部博士学科点新教师基金课题(20100101120058)的资助下,本文开展了UHTCC-FGC梁弯曲疲劳性能试验研究。试验浇筑了普通混凝土梁和UHTCC-FGC梁共13根,其中普通混凝土梁为4根,UHTCC-FGC梁为9根。UHTCC-FGC梁的UHTCC层的厚度分别为40mm和50mm。通过静载试验确定梁的弯曲极限荷载,并且分别取应力水平为0.7-0.9做疲劳试验,疲劳试验中的应力比为0.2,以防止加载中试验机和试件会产生摩擦。疲劳加载频率为2Hz和4Hz,荷载控制,正弦波。试验主要研究UHTCC-FGC梁的疲劳寿命的大小,变形能力和承载能力,承受疲劳荷载时受拉区裂缝的数量与裂缝开展模式,试验结束时梁的破坏状态,以及疲劳加载时钢筋与UHTCC的粘结能力等。更多还原

【Abstract】 Concrete, with the advantages of low price and easily accessibility of its raw materials, is widely used in civil engineering construction. But the brittle characteristic of concrete, especially under tensile stress is one of its major limitations. The formation and evolution of cracks in concrete structure will reduce its stiffness and durability. With the properties of high ductility and pseudo strain-hardening behaviour, Ultra high toughness cementitious composites(UHTCC) is an ideal material to replace concrete to compress its brittle failure.The ultimate tensile strain of UHTCC is about3%～7%, and the average width of UHTCC can be controlled below100μm-sometimes even below40μm. However the wide use of UHTCC is limited by its high cost, thus it’s reasonable to use it to replace concrete in the key parts of a structure. Previous monotonic experimental results have shown that the failure of UHTCC-FGC beams (i.e. functionally graded composite beams crack-controlled by UHTCC) occurs with the formation of multiple cracks, thus leading to higher deformability and load carrying capacity of UHTCC-FGC beams than reinforced concrete.This research which is financially supported by Natural Science Foundation of China (No.51008270) and Specialized Research Fund for the Doctoral Program of Higher Education of China(No.20100101120058) focuses on mechanical performances of UHTCC-FGC beams under fatigue loading. A total of13beams including4plain concrete beams and9UHTCC-FGC beams were casted, and the stress level is set between0.7and0.9. The constant ratio of minimum stress to maximum stress is set to0.2to avoid any impact and slip between the loading machine and the specimens during testing. All the specimens will be subjected to sinusoidal cyclic loading at2Hz and4Hz frequency. During the experiments, the fatigue life, deformability and loading capacity of UHTCC-FGC beams will be measured and recorded. Meanwhile, the development of cracks and the failure pattern of UHTCC-FGC beams during the test will be observed at the same time.更多还原