基于断裂力学的锚拉板疲劳寿命评估

Assessment of Fatigue Life for Anchor Plates Based on Fracture Mechanics

为研究斜拉桥锚拉板结构的疲劳性能，以一座叠合梁斜拉桥为例，采用最新钢桥规范的疲劳荷载模型加载并按雨流法处理计算了疲劳荷栽谱，结合空间实体有限元模型，识别了锚拉板的典型构造细节并获得疲劳应力谱；在典型构造细节处引入初始表面裂纹，计算了裂纹尖端的应力强度因子，回归分析得到应力强度因子与裂纹尺寸的关系式，代入Paris公式积分得到了各典型构造细节的疲劳寿命，从而建立了基于断裂力学的锚拉板疲劳寿命分析方法．研究结果表明：基于断裂力学方法得到的锚拉板疲劳寿命超过了100年，满足设计及使用要求；裂纹初期扩展很慢，当尺寸达到10mm时，已消耗了60％～80％的疲劳寿命，应及时加以补强．

To investigate bridge was taken for example the fatigue performance of anchor plates, a composite beam cable-stayed in this study. A loading model in the new standard for steel bridge and the rain-flow method were applied to gain fatigue load spectrum, combined with a three dimensional finite ele- ment model to identify the typical structural details and fatigue stress spectrum of anchor plates. Initial surface cracks were imported in the typical details, and stress intensity factors of crack tips were calculat- ed. The stress intensity factor and crack size were regressed by substituting in Paris formula, which were integrated to gain the fatigue life of typical structural details. The assessment of fatigue life for anchor plates based on fracture mechanics was then established. The results show that the fatigue life for anchor plate based on fracture mechanics is over 100 years, satisfying the requirement of design and utilization; the crack is developed very slowly in the early time, but when it reaches 10 millimeters, 50% to 80% of its fatigue life is consumed. Therefore, reinforcement should be timely applied to the anchor plates.