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

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.