考虑长期腐蚀影响的古建木结构极限寿命预测

针对长期环境腐蚀对古木结构的性能和损伤程度的影响,基于蒙特卡洛方法结合Gerhards/Weibull模型提出了古建筑木结构关键构件的承载力/变形值极限寿命预测方法.首先研究了腐朽、虫蛀等腐蚀环境对构件的截面尺寸和强度的影响,分别在承载能力和正常使用极限状态下建立构件的承载力/变形值的时变模型;其次利用蒙特卡洛方法,考虑构件尺寸、强度、荷载等随机参数对木结构关键构件的影响,给出具有一定可靠度的极限寿命预测方法与置信区间,并对结构做出相应的决策判断.最后以某历史文化民居选取的单榀框架来验证所提方法的有效性.结果表明:在长期腐蚀条件下,构件抗力随时间减小,变形值随时间增大,对两者变化规律进行时变分析是评估的关键;Gerhards和Weibull模型结合蒙特卡洛方法可以较好地对木结构梁、柱关键构件的极限寿命进行预测;综合考虑承载力和变形值能够更真实地反映结构的极限寿命.

Ultimate life prognosis of ancient wood structure buildings considering the effect of long-term corrosion

Aiming at the effects of long-term environmental corrosion on ancient wood structures, the paper proposed a time-dependent reliability prognosis method of bearing capacity and deformation limit of pivotal component, which is based on monte-carlo method and Gerhards/weibull model. Firstly, the effects of rot and worm attacking on the size of section and strength degradation were studied, and then the time-dependent models of bearing capacity and deformation value were built under ultimate andSserviceabilitySlimitSstates respectively. By adopting Monte Carlo method, the effect of the some random parameters, such as strength, strength and load on pivotal component was analyzed, and ultimate life prognosis method and confidence interval of certain reliability were obtained, whereby the decision was made. Finally, the validity of the method proposed was validated by a frame from historical and cultural folk house. The results indicate that: (1) the resistance of the component decreases with time under long-term corrosion, while the deformation increases; (2) time-dependent analysis on the change regulation of the two parameters is the key to the evaluation; (3) the ultimate life of beams, columns and other important components can be forecasted well by using Gerhards/Weibull model and monte-carlo method. Besides, the ultimate life of the structure can be reflected more accurately by considering both bearing capacity and deformation value.