Influence of Local Density on Concentrated Static Load Performance of Oriented Strandboard

Fourteen 1,220 by 2,440 by 11.1-mm commercial Oriented Strandboard (OSB) panels were X-ray scanned to obtain horizontal density matrices. Localized densities around the concentrated static load (CSL) testing points of the panels were calculated prior to the CSL test. A linear regression analysis was conducted to assess the impact of the localized density on CSL performance. The results indicated that both deflection and ultimate load were highly correlated with the local density. Deflection and ultimate load were somewhat correlated (R2 = 0.52). The CSL deflection decreased and ultimate load increased significantly with increasing local density. The impact of local density on ultimate load was greater than on deflection. Horizontal density variation is inherent in OSB manufacturing processes, especially in the mat forming process. A number of factors, including evenness of strands in the metering bin, condition of picker rolls and dissolving rolls, and strand and fines surging, can affect horizontal density distribution. OSB panels with a high degree of variation in horizontal panel density may cause low density spots that increase the chance of failure in CSL test. It is therefore crucial to minimize the occurrence of very low density areas in order to reduce the odds of ultimate load failure. Reducing density variability allows OSB companies to increase the CSL properties of their products, which would otherwise need to be done by making the panel denser. Improving horizontal density uniformity allows for lowering of the average panel density, which reduces the manufacturing cost and helps improve the company's bottom line.