中文摘要：

对16m长全尺寸预应力混凝土梁桥原型进行三点弯曲疲劳试验，利用数字图像相关（Digital Image Correlation，DIC）方法获得集中力作用点附近区域的变形场及应变场信息。经过200万次疲劳循环作用．研究了梁体侧面裂缝的萌生、成核、扩展机理。试验结果表明，主裂缝由次裂缝诱发萌生，主裂缝随疲劳循环次数而扩展，50万次之前的扩展速率明显大于50万次以后的扩展速率。随着主裂缝的扩展。次裂缝略有闭合。疲劳荷载不超过设计荷栽时，钢绞线具有较好的拉结作用，预应力混凝土梁裂缝开展缓慢稳定，有明显的刚度退化。与传统电测法相比，DIC方法可准确观测全场裂缝扩展过程，可应用于对预应力桥梁的分析研究。

英文摘要：

Three point bending fatigue test was carried on full-size prototype of a 16m length prestressed concrete girder bridges. The strain field and strain field information near the loading point were obtained using Digital Image Correlation （DIC） method. After 2 million times of fatigue cycle, the crack initiation, nucleation and growth mechanism of the beam were studied. The experiment results show that, the main crack initiation induced by crack, the main crack extension according to the fatigue cycles, the extension rate before 500000 cycles significantly greater than that after 500000 cycles. Crack closure slightly with the expansion of the main crack. The fatigue load is less than the design load, steel strand has good tie effect, crack developing slowly and steady, the stiffness degradate obviously. Compared with the traditional measurement method, DIC method can observe the crack extension process accurately, which can be applied to analysis and research of prestressed concrete bridges.