考虑环境变温作用的大跨桥梁疲劳损伤分析

基于桥梁健康监测系统记录的温度时程数据,研究钢箱梁顶板、底板的温度变化特征和规律,利用间接耦合法将热分析的温度数据作为体荷载施加于结构多尺度有限元模型,获得了环境变温引起的结构应力,实现了从热分析到结构应力的分析.然后,利用健康监测系统记录的应变时程数据,考察车辆荷载和环境变温所引起的应变特征的差异,提取和分离出由环境变温和车辆荷载引起的应变时程,并与模拟得到的应力时程加以对比和相互验证,在此基础上利用连续介质损伤力学理论分析车辆荷载单独作用以及车辆和环境变温交互作用所引起的桥梁累积损伤.结果表明:提出的损伤分析流程可实现桥梁关键部位在考虑环境变温和车辆荷载两种因素作用下的损伤分析.环境变温单独作用所引起的疲劳损伤很小,基本可以忽略,但两者交互作用所引起的结构疲劳损伤相对于车辆单独作用下的损伤有显著差异.在服役初期环境变温的作用并不显著,随着疲劳损伤的不断增加,这种交互作用对结构疲劳损伤累积的影响会愈发明显,即环境温度变化引起的荷载会加速结构服役中后期疲劳损伤的累积速率,进而对结构疲劳寿命产生显著影响.

Analysis on Fatigue Damage of Long-span Bridges ConsideringEffect of Environment Varying-temperature

Based on temperature-history data recorded by structural health monitoring system (SHMS) installed on long-span bridge,the characteristics of the temperature in the top deck and bottom deck of the steel box girder was studied. According to the indirect coupling method,temperature was regarded as body load and applied to three-dimensional multi-scale finite element (FE) model. Structural stress induced by temperature can be obtained and the analysis from thermal to the structure was realized. And then,based on the strain data from SHMS,the difference of strain characteristics induced individually by vehicle loads and environment temperature were investigated. Strain histories caused by the above factors were separated and extracted,and they were compared with the results by the FE simulation. Finally,based on the continuum damage mechanics,the cumulative fatigue damage of the bridge was induced by vehicle load separately as well as the interaction of vehicle load and environment temperature. The results show that the analysis flow of fatigue damage proposed in this paper can realize fatigue damage analysis at key locations of bridge under the action of environmental temperature and vehicle load. Fatigue damage caused by the temperature alone is small and can be ignored. But the fatigue damage caused by the interaction of these two loads has significant difference with that caused by the vehicle alone. At the beginning of the service periods,the influence of temperature on damage is not significant,but with the increase of fatigue damage,the influence of the interaction of these two loads becomes more prominent. That indicates that loads induced by temperature change accelerate the rate of fatigue damage accumulation at the mid-late service periods,and have a significant impact on the structure fatigue life.