Lateral Performance of Traditional Heavy Timber Frames with Mortise-Tenon Joints Retrofitted Using Self-Tapping Screws

This paper presents the test results of three 1/2-scaled Chinese traditional mortise-tenon jointed beam-column frames, initially loaded to damage and retrofitted by use of self-tapping screws and retested under a constant vertical load and cyclic lateral loading. The retrofitting effect on a bare frame and two otherwise the same frames with partial (with a window opening) and full infill is discussed in terms of the damage distribution, envelope curve properties, strength degradation, and equivalent viscous damping ratio. The results indicate that the retrofitted frames exhibited smaller stiffness (27% the least), large deformability (155% the most), higher damping ratios (118% the most), and similar strength degradation (less than 40% decrease) from primary cycles to trailing cycles. The maximum loads of the rested bare frames, partially infilled frame, and fully infilled frame reached 55%, 85%, and 125% of those from the initial testing, respectively. It is also believed that the retrofitting of the fork-leg joints of the columns to the bottom beams was unsuccessful using screws and may be unnecessary for the better function of the infill panels. The retrofitting of the mortise-tenon joints next to the main and secondary beams above the infill panels are, however, very important, especially in terms of preventing pulling-out deformation of the joints because it is closely related to the shear stiffness of the infill panels.