基础竖向周期激励下GFRP圆弧拱面内动力稳定性实验研究

EXPERIMENTAL STUDY ON IN-PLANE DYNAMIC STABILITY OF GFRP CIRCULAR ARCH UNDER A VERTICAL HARMONIC BASE EXCITATION

该文为探究铺层角度对基础竖向激励下GFRP圆弧拱平面内动力稳定性能的影响,开展了系统的实验研究。设计了6组不同铺层角度的圆弧拱试件,利用TIRA激振器模拟输出基础竖向周期激励,采用NDI三维动态采集仪采集圆弧拱的竖向动位移,根据测得拱的面内自由振动响应,分别通过快速傅里叶变换和自由衰减法获得拱的自振频率和阻尼比。通过扫频实测了GFRP拱的动力不稳定域边界,并与有限元计算结果进行对比,基本吻合。研究表明:当外部频率约为结构自身频率两倍时,结构会出现激烈的面内反对称振动现象,即为参数共振失稳;当激励加速度小于临界激发加速度时,拱处于定态振动;外激励大于临界激发加速度时,GFRP拱出现参数振动,并且随着加速度的增大,拱的振动愈发激烈;随着铺层角度的增大,拱的自振频率和临界激发加速度逐渐减小,阻尼比与不稳定域范围逐渐增大。

The purpose of this study is to investigate the dynamic stability of GFRP circular arches with different lay-up angles under vertical excitations.Thusly,a systematic experimental study is performed.Six groups of circular arches with different lamination are designed,the vertical periodic vibration of foundation was simulated by applying TIRA series vibrator.The vertical displacement of circular arch was collected by NDI 3D dynamic acquisition instrument.According to the displacement data,free vibration frequency and damping ratio of the arch are obtained by fast Fourier transform and free attenuation method.The boundary of dynamic instability region of GFRP arch was measured by frequency sweep.The experimental results were compared with the finite element results,and the results show that when the external load frequency is about 2 times of the natural frequency of the structure,the structure has an intense in-plane antisymmetric parametric resonance.When the excitation acceleration is less than the critical excitation acceleration,the structure will not be unstable.The greater is the acceleration of external excitation,the easier does the parameter resonance phenomenon occur.With the increase of the lamination angle,the structural frequency and critical excitation acceleration decreases,and the damping ratio and the range of instability region increase gradually.