Abstract: Anchoring frame beams are at risk of anchor bolt fracturing or pulling out at joints, which can lead to overall failure under high-intensity seismic action. Based on the concept of flexible damping, buffer springs were installed at the external anchor heads of frame beam joints, and a shaking table model test was conducted on a shallow overburden-rock slope with a geometric scale of 12. The seismic responses, including slope acceleration and anchor bolt axial force, were compared with and without the flexible external anchor heads under high-intensity seismic ground motions (artificial seismic waves and Wenchuan earthquake wave). Specifically, the variation in the anchor bolt force reduction ratio with different buffer spring stiffnesses was analyzed, and the benefits of spring anchor heads on seismic energy response and vibration-induced cumulative damage in anchor bolts were explored. The research results indicated that installing flexible external anchor heads led to a reduction in the amplification factor of Arias intensity. As the stiffness of the buffer spring decreased, the reduction ratio of the anchor bolt dynamic axial force ranged from 72% to 89%, and post-earthquake prestress loss of the anchor bolts was effectively reduced. Spectral analysis of anchor rod dynamic axial forces and linear cumulative damage calculations at the anchoring interface demonstrated that the energy response in the mid-to-high-frequency range was significantly attenuated, which could lead to structural damage. Both the cumulative tensile fatigue damage of the anchor bolt and the cumulative shear fatigue damage at the grout-anchor interface were both significantly reduced. The adoption of flexible external anchor heads effectively controlled structural damage during high-intensity seismic events.

Key words: anchoring frame beam, flexible external anchor structure, shaking table test, time-frequency characteristics, linear cumulative damage