Performance degradation by column foot damage: From column foot joints to frames

Abstract

This study investigated the performance degradation brought by column foot damage on both joint level and frame level. Three column foot joint specimens, characterized by different damage indexes (defined as the ratio of absent sectional width to radius), were cyclically tested. Typical deformation modes of the damaged joints were identified. Mechanical behavior degradation of the joint specimens was quantified. The influence of the column foot damage on a traditional timber frame’s lateral performance was further analyzed. The test indicated that the column foot damage decreased the uplift deformation of a column during the rotation of a column foot joint. Both the mechanical performance of a column foot joint and the frame was approximately linearly degraded by the column foot damage. With a damage index of 0.6, the joints’ initial rotational stiffness and moment-resisting capacity decreased 40 %; the elastic lateral stiffness, the peak load and the cumulative energy dissipation of the frame reduced 31 %, 20 % and 11 %, respectively. Varying the column dimensions did not considerably change the degradation pattern in the elastic stiffness and cumulative energy dissipation of the frame. However, changing the column diameter significantly influenced the damage impact tendency on the lateral load-resisting capacity of the frame. Specifically, with a 30 % variation in the column diameter, the degradation of the column foot damage on the peak load ranged from 12 % to 30 %.