Experimental study of the effects of continuous rod hold-down anchorages on the cyclic response of wood frame shear walls

When designing mid-rise wood frame buildings in high seismicity areas, overturning moments induce large tensile forces in the anchoring system that cannot be resisted by conventional discrete hold-downs. To address this issue, continuous rod hold-downs are used instead to transfer the generated tensile loads to the foundation. However, investigations on the lateral response of wood frame walls employing this anchorage system are quite limited. This paper presents an experimental-numerical study aimed at providing a better understanding of the response of such walls under lateral loads. Four specimens with different configurations were tested under lateral cyclic load, and their behavior was compared with that of walls with discrete hold-downs. Results showed that employing the continuous rod system increases the wall strength by 35.8%, with the specimens behaving elastically up to drifts of about 0.8%. The walls exhibited a marked stiffness degradation during the tests, keeping a residual value of about 15-20% of the initial stiffness. Further analyses showed that the Special Design Provisions for Wind and Seismic (SDPWS) guidelines underestimate the wall strengths by 39.9% and overestimate the stiffnesses by 37.5%, on average. Finally, a nonlinear model was developed to investigate the specimens of this research in depth, showing a special failure pattern that concentrates the damage in the nails located at the central studs of the wall.

Automated summary

This research conducted an experimental-numerical study on the response of wood frame walls using continuous rod hold-downs under lateral loads. It was found that this system significantly enhances wall strength, but also leads to noticeable stiffness degradation during testing. Further analyses revealed underestimations of wall strengths and overestimations of stiffness by the SDPWS guidelines.