Z24桥阻尼比长期变化影响因素及影响规律

Long-term characteristics of damping ratio of the Z24 bridge influenced by different factors

为研究Z24桥阻尼比长期变化的影响因素及影响规律,首先利用该桥长期监测数据,采用加速度时间序列语义分割获取了大量的加速度自由衰减响应,由指数衰减法得到了为期约10个月的一阶阻尼比识别结果;然后分析结构温度、振动剧烈程度、结构损伤对阻尼比的影响规律。结果表明:Z24桥一阶阻尼比与结构温度具有极强的相关性,0℃以下时段,阻尼比随结构温度降低呈先增大后减小的非线性变化;0℃以上时段,阻尼比随结构温度升高而线性减小,二者相关系数最高可达0.98;环境激励(桥下通行车辆)与重物坠落激励下,阻尼比受振动剧烈程度的影响均无明显规律可循;阻尼比对各种结构损伤的存在与否亦无确切的指示性作用,由阻尼比获取更有效的损伤特征仍有待于进一步的研究。上述因素的影响规律应在结构振动控制设计、损伤识别等阻尼比应用场景中得到考虑,以提升结果的合理性与可靠性。

To investigate the long-term characteristics of damping ratio of the Z24 bridge influenced by different factors,a time series semantic segmentation method was introduced to extract free attenuation data segments from monitored accelerations of the Z24 bridge.Then,the data of about 10-month damping ratio of 1st vibration mode were calculated using exponential attenuation method.Based on the calculated damping ratio,the influences of three factors including temperature,vibration intensity,and structural damage were analyzed.The results show that there exists a strong correlation between the damping ratio of the Z24 bridge and temperature variation.Specifically,the damping ratio exhibits an increasing trend followed by a decreasing trend after the temperature drops below 0℃,while the damping ratio exhibits a linearly decreasing trend after the temperature goes beyond 0℃,and that the correlation coefficient even reaches 0.98.The vibration intensity presents little impact on the damping ratio under the simultaneous action of excitations:vehicles passing below the bridge and dropping weight on the bridge.The structural damage also exhibits very limited influence on the damping ratio,thus further investigation is still required in the future to obtain effective damage features based on the identified damping ratio.The influences of the above factors should be considered in damping ratio-related applications including structural control and damage detection to achieve reasonable and reliable results.