Experimental testing of anchoring devices for bottom rails in partially anchored timber frame shear walls

Källsner and Girhammar have presented a new plastic design method of wood-framed shear walls at ultimate limit state. This method allows the designer to calculate the load-carrying capacity of shear walls partially anchored, where the leading stud is not anchored against the uplift.The anchorage system of shear walls is provided from anchor bolts and hold downs. Anchor bolts provide horizontal shear continuity between the bottom rail and the foundation. Hold downs are directly connected from the vertical end stud to the foundation. When hold downs are not provided, the bottom row of nails transmits the vertical forces in the sheathing to the bottom rail (instead of the vertical stud) where the anchor bolts will further transmit the forces into the foundation.Because of the eccentric load transfer, transverse bending is created in the bottom rail and splitting often occurs.Bottom rail experimentally studied with respect to two primary failure modes, splitting along the bottom of the bottom rail due to cross-wise bending and splitting along the edge side of the bottom rail due forces perpendicular to the grain for the sheathing-to-framing connections.The parameters varied are the location of the anchor bolt, the size of the washer and the orientation of the pith.The bottom rail was subjected to loading perpendicular to grain through one-sided sheathing.In this report the different test series are presented. Three series were conducted depending on the location on the anchor bolt. In each series different sets were studied depending on the size of the washer and in each set the pith was placed upwards or downwards.The tests showed three different failure modes. In addition to the failure modes that the testing program was aimed at, splitting along the bottom or side of the bottom rail, the final failure was due to plastic bending and withdrawal of the sheathing-to-framing nails.The results show that the size of the washer and the position of the bolt have a significant influence on the maximum load and the failure modes. It was found that decreasing the distance of the washer to the loaded edge of the bottom rail increases the maximum load.Godkänd; 2011; 20110620 (giucap