Abstract:
To investigate the failure modes and the dynamic response of a double-eave hip-and-gable timber structure under three-dimensional (3D) ground motions, a 1:5 scale model was designed and fabricated based on a typical Qing-style prototype and tested on a shaking table under unidirectional, bidirectional, and three-directional ground motions. The El Centro, Chichi, and artificial waves were applied to the model at frequent, design-basis, and rare earthquake levels of intensity 8. Failure modes, the evolution of dynamic characteristics, of seismic responses, and of energy dissipation distribution were examined, with a special attention to the effect of vertical ground motion on the horizontal seismic responses. The research results indicate that the primary failure modes involved tenon pull-out, bracket splitting, and column footing slippage. Due to the asymmetry of the spatial framework, the initial natural frequencies in the
X and
Y directions are 2.34 Hz and 2.40 Hz, and the damping ratios are 6.1% and 5.0%, respectively. After a rare earthquake, the frequency drop and damping increase are more significant in the
X direction than in the
Y direction. Compared to horizontal excitations, 3D ground motions more easily excite higher-order modes of the structure, significantly amplifying the horizontal accelerations at the upper and lower eaves, but has a minor effect on the overall displacement, with the amplification effect mainly concentrated at the column feet. Under a rare earthquake of intensity 8, the maximum inter-storey drift ratio was 1/33, meeting the code limit of 1/30. The influence of 3D ground motions on energy dissipation is also concentrated at the column feet, where the energy dissipation contribution increases with the intensity of seismic excitations. The overall energy dissipation exhibits a distribution pattern of "strong below and weak above," indicating the good deformation and energy dissipation capacity.