Design against brittle failure of bottom rails in shear walls

The authors have developed a new plastic design method for light-framed timber shear walls, which is capable of analysing the load-bearing capacity of partially anchored shear walls. For proper application of the plastic method it is necessary to ensure ductile behaviour of the sheathing-to-framing joints and to avoid brittle failure of the bottom rail. In a partially anchored shear wall, the tying down forces are developed in the sheathing-to-framing joints along the bottom rail, which may introduce a brittle type of failure of the bottom rail that needs to be eliminated in order for the plastic method to be applicable. This paper deals with design of anchor bolts needed to tie down the bottom rail properly and it describes experimental results for proper design of washers for anchor bolts to avoid these splitting failures of the bottom rail. The effect of different washer sizes and location of the anchor bolts on the failure load when splitting of the bottom rail occurs is presented. The tests indicate that the failure load depends on the distance from the edge of the washer to the loaded edge of the bottom rail. An explicit design equation for the capacity of the bottom rail is presented.