Influence of panel structure on wood to flakeboard nail connection properties

• Main Author: Wang, Sunguo
• Language: English
• Published: 2009
• Online Access: http://hdl.handle.net/2429/11493

Oriented Strand Board (OSB) or flakeboard is widely used in the building industry as different components such as shear walls, floors, roofs and underlayments. The performance of OSB to lumber connections has been investigated by many researchers, but its relationship to OSB or flakeboard panel structure has never been systematically studied. The study presented in this thesis focuses on this research scope. The research project was divided into two parts. Preliminary tests (Phase I) on OSB-tolumber nail connections were conducted using 11 mm commercial OSB panels as side members and Spruce-Pine-Fir (SPF) lumber as main members. Several combinations of OSB specimen sizes, nailing patterns and test set-ups were investigated. Tensile loads were applied statically along the longitudinal direction of the lumber member, but perpendicular to the nail shank for all specimens. Both the single nail and the two-nail combination patterns were examined in OSB specimen I (50x240x11 mm) and specimen II (240x240x11 mm). Loading directions relative to OSB face flake orientation were studied for specimen II. The results showed that the chosen test jigs were suitable for small sized OSB-to-lumber nailed connections. The new set-up with specimen II was more efficient for small scale nail connection testing since the specimen can be easily adjusted to study the influence of the loading directions, nailing patterns and multiple nailing; hence, more information could be obtained. Two main failure modes, pullthrough and pull-out, were observed in the preliminary tests. The second part of the project (Phase II) included the main tests. Three principal processing parameters, flake orientation, flake thickness and board density, were considered in the experimental design of flakeboard structures. A Monte Carlo computer program WinMat® was used to simulate mat structure patterns and their corresponding horizontal density profiles. A robot-based formation system was applied to build flakeboard mats, which ensured exactly the same mat structures as defined in the computer program. Predefined and laboratory-manufactured oriented and random flakeboards were then conditioned and assembled with 38x89 mm SPF lumber into nail connections. Single nail lateral resistance tests were conducted to study the effects of failure modes, panel types and loading directions on nail-connection properties. The results showed that: 1) most nail properties for the specimens that failed in the pull-out mode were significantly different from those in the pull-through mode; 2) the specimens that failed in the pull-out mode had higher initial stiffness and connection strength (maximum, yield and ultimate loads) than those in the pull-through mode; 3) compared to OSB panels, random panels had higher connection strength for the pull-through mode, larger maximum displacement for the pull-out mode, and higher maximum and ultimate strain energies, and larger ultimate displacement for both failure modes; 4) the 90° loading direction in OSB panels indicated significantly different nail properties for both pull-out and pull-through modes, compared with the 0° and 45° loading directions, but there were no significant differences in nail properties between 0° and 45° loading directions under the pull-through mode; 5) there was significant difference in connection strength between 0° and 45° loading directions under the pull-out mode; 6) from regression analyses, most of the OSB or random flakeboard to SPF lumber nail connection properties were affected by different combinations of panel local density (LD), board to flake thickness ratio (TR), and lumber specific gravity (G); 7) a parametric study was carried out to show a potential application of the information developed in this paper; generally, higher lumber specific gravity and panel local density mostly showed better initial stiffness and connection strength (loads) within the regression ranges and fixed lumber or flakeboard properties. However, the effect of panel to flake thickness ratio is comparatively complex. Different types of connection or loading conditions may produce opposite trends. Hankinson's equation predicts very close initial stiffness and maximum load to measured values at 45° loading angle based on nail properties along and across OSB face flake alignment, and may also have good predictions on the nail performance at any loading angle, which will be verified in the further study.