Källsner and Girhammar [1] have presented a new plastic design method for 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 fully anchored against uplift.
The parameters varied are the size of the washer and the orientation of the pith. The bottom rail was subjected to loading perpendicular to grain through two-sided sheathing. In this report the different set of series are presented. Five sets were conducted depending on the size of the washer and in each set the pith was placed upwards and downwards.
Project contact is Y.H. Chui at the University of Alberta
Summary
Wood shear wall systems with insulated sheathing are commonly implemented to meet a higher standard of building energy efficiency. Adding a layer of continuous thermal insulation exterior to the cavity insulation, insulated sheathing, to reduce thermal bridging is getting more popular in practice. The impact of the intermediated insulation on racking performance of shear walls has recently been investigated by experimental studies. The test data provides better understanding on the influence of various construction configurations. Nevertheless, there is a need to provide an alternative approach which enables engineers to calculate the design capacities of shear walls with insulated sheathing. In this project, the available analytical models and approaches for determining shear resistances of shear walls are reviewed and compared. A new modified analytical model will be developed based on comparisons and the test results.
Currently the massive timber shear walls are mainly made from Cross Laminated Timber (CLT), which possesses a high in-plane shear strength and rigidity. But only part of its elements (mainly the vertically aligned laminae) are engaged in carrying the vertical load and that could be a limitation when designing taller timber structures or wherever higher vertical load is present. This project studied alternative solutions to massive timber shear wall system, based on Nailed Laminated Timber (NLT) and post laminated LVL (Laminated Veneer Lumber).
The test was conducted on three levels: shear test on glue/nail line, bending-shear test on a small element, and full size wall test under lateral loading. The former two tests investigated the properties of basic elements in NLT and post laminated LVL. The results were used to design and predict the performance of full size shear walls.
The NLT walls were tested under two conditions: without sheathing and with plywood sheathing. The wall without sheathing had the lowest load-carrying capacity and lowest stiffness. Adding plywood sheathing significantly increased its strength and stiffness. The failure in the wall with sheathing was at the sheathing connections, in the forms of nail withdrawal, nail head pull through, and nail breakage. The NLT wall with sheathing had a peak load up to 60% higher than the comparable light wood frame wall, also with a higher stiffness and better ductility. NLT shear walls have an internal energy dissipating capacity which CLT and post laminated LVL walls lack. The post laminated LVL walls behaved as a rigid plate under lateral loading, with little internal deformation. The failure occurred at the holdowns not within the wall. The size effect of its shear strength was studied and an equation was developed to calculate the shear strength of a large size wall plate.
Both products have efficient vertical load bearing mechanism by arranging all elements in the vertical direction. They may serve as alternative to light wood frame walls or CLT walls. Some guidelines for the application and design of NLT shear walls and post laminated LVL shear walls were proposed.
