Characterization of the racking performarce of nailed and stapled ligth-frame Shear walls.

Abstract

Shear walls are the major components of the Lateral-Force-Resisting System (LFRS) in lightframe wood buildings. With the growing popularity of mid-rise prefabricated light-frame wood construction, engineers need basic design information on the shear walls to design and produce safe structures in case of high winds or earthquakes. The racking resistance of lightframe shear walls depends on many factors, including sheathing and hold-down devices and, most importantly, sheathing-to-framing fastenings. While the performance of nailed shear walls has been studied extensively, and design information is included in the design codes, there is little information on stapled shear walls, especially in the US and Canada. The cost of staples is significantly less than of equivalent nails; hence, the use of staples instead of nails would allow cost savings in mass production if they provide sufficient resistance and displacement capacity in the engineered shear walls. This thesis presents the results of a study which was focused on the comparison of the performance of nailed and stapled shear walls in laboratory tests under monotonic and cyclic loading in accordance with ASTM E564 and E2126, respectively. Several series of tests were performed on 2.4-m (8-ft) square shear walls with 11-mm (7/16-in) OSB sheathing with various hold-downs and various patterns of staples and nails: 5-cm (2-in), 10-cm (4-in) and 15-cm (6-in) spacing and 19-mm and 10-mm edge/end distances of connector. The staples were gauge 16: 50-mm (2-in) long with 11-mm (7/16-in) crown. The nails were power-driven bright common steel wire nails gauge 8d: 63- mm (2½-in) long with 2.87-mm (0.113-in) diameter. The main results revealed a similar racking performance for stapled and nailed shear walls, in terms of initial stiffness, maximum displacement, maximum load, equivalent stiffness and equivalent viscous damping ratio. Moreover, the failure of the wall is a combination of different failure modes in the connectors where the end/edge distance is important. Finally, the principal highlight for stapled shear walls is the less splitting framing when the end/edge spacing fastener is 5-cm (2-in) from the end/edge of the sheathing