泉州镇国塔抗震能力探讨

An exploration on aseismic capability of Quanzhou Zhenguo Pagoda

使用SLJ-100型三分向力平衡加速度计监测了泉州镇国塔在环境振动激励下的加速度响应,基于MATLAB平台编制的数据处理、分析、模态识别程序,识别出镇国塔平动前三阶模态频率、阻尼比和振型;并依据相关文献,对测试结果进行修正,得到大、中震地震作用下镇国塔的自振周期和阻尼比。基于镇国塔结构动力特性,结合镇国塔实测的几何尺寸和结构构造,应用振型分解反应谱法和冲量法对镇国塔分别在水平地震作用下和竖向地震作用下进行抗震能力分析与评估。结果表明:塔体截面抗水平地震作用的能力,在"小震"和"中震"作用下是足够的,在"大震"作用下则严重不足;塔体截面抗竖向地震作用的能力有富余;该石塔"小震"下处于弹性状态,"中震"下进入塑性状态,"大震"下将出现严重破坏。上述结果可为古建筑抗震减灾提供参考。

By means of Type SLJ-100 three-component dynamic balance accelerometer,the acceleration response of Zhenguo Pagoda in Quanzhou was monitored under the influence of environmental vibrations.Then the first three shear modal frequency,damping ratio and modes were identified according to the data processing,analysis and modal identification programs by MATLAB language.The testing results were modified through relevant literatures in order to attain the natural vibration period and damping ratio of the Pagoda upon major and medium shocks.Based on the upper structural dynamic characteristics together with the measured physical dimension and structural construction of the Pagoda,the method of mode-decomposition response spectrum and the impulse momentum method were respectively applied to analysing and evaluating the aseismic capability of Zhenguo Pagoda under the effects of horizontal and vertical earthquakes.The results demonstrate that the capability for anti-horizontal seismic effect of tower cross section is sufficient under the influence of 'minor earthquake' and 'medium earthquake',while seriously insufficient under the effect of 'major earthquake'.However,the capability for anti-vertical seismic effect of tower cross section is abundant.The pagoda is in the elastic stage under minor earthquake and becomes plastic stage under medium earthquake,but it will be seriously damaged under major earthquake.The study sheds some lights in earthquake protection of ancient architectures.