Behavior of Light-Framed Wood Roof-to-Wall Connectors Using Aged Lumber and Multiple Connection Mechanisms

• Published in: Journal of performance of constructed facilities 2012-02, Vol.26 (1), p.26-37
• Main Authors: Edmonson, William C, Schiff, Scott D, Nielson, Bryant G
• Format: Article
• Language: English
• Subjects: Aids; Applied sciences; Building structure; Buildings; Buildings. Public works; Connectors; Construction; Construction (buildings and works); Exact sciences and technology; External envelopes; Joints; Retrofitting; Strength; TECHNICAL PAPERS; Wood; Wood structure
• ISSN: 0887-3828; 1943-5509
• DOI: 10.1061/(ASCE)CF.1943-5509.0000201

Ensuring a complete load path in light-framed wood structures is critical in providing proper load transfer during wind and seismic events. Roof-to-wall metal-connectors are often used to accomplish this goal. Currently, the design and construction community utilizes published metal connector capacities found in manufacturer documentation or other design aids to properly size connectors for a given demand. However, with the ever-increasing trend of using recycled dimensioned lumber and in situ retrofits of older buildings, the limited supply of research in this area is becoming more apparent. At present, the state-of-the-practice does not provide guidance to account for changes in material properties in structurally sound reclaimed or aged lumber. This study uses dimensioned lumber that was extracted from decommissioned buildings, originally built in the 1960s, to examine the effect of reclaimed dimensioned lumber on the design strength of connections by using metal-connectors. Through the use of testing on over 150 samples, this study identifies issues with the current design practice. The metal-connectors show a 20% reduction in uplift design strength, whereas they exhibit a 21% increase in the in-plane design capacity when used in conjunction with the reclaimed lumber. The difference in design capacity for out-of-plane loading appears to be statistically insignificant. As a secondary portion of this study, the design capacities of roof-to-wall connections utilizing two 16d common toenails and a commercially available metal connector were examined. Independent and combined capacities are evaluated. The presence of toenails in roof-to-wall connections is a common situation, as toenails can be used as a construction aid during framing, or toenails can be artifacts left from the original time of construction in retrofit applications. The design capacities of the toenails were determined to be additive to the design capacities of the metal connector for uni-axial loading in uplift or out-of-plane. As a result of rafter splitting, the presence of toenails detracted from the design capacity of the metal connector when loaded uni-axially in-plane.