Effect of wetting and fungal degradation on the withdrawal capacity of stainless-steel screws in radiata pine

Abstract

The effects of exposure to two decay fungi on the withdrawal capacity of stainless-steel screws inserted in the face and end grain of radiata pine specimens were assessed. Wetting followed by steam sterilization significantly increased capacity by 55–65%. Exposure to a brown (Fomitopsis ostreiformis) or white rot fungus (Pycnoporus coccineus) over 25 weeks was associated with 81–83% and 24–42% losses in withdrawal capacity, respectively. Comparison of experimental results with those predicted from design codes (Australia, Europe, US) showed an overestimation of the screw withdrawal capacity for the control specimens and highlighted the risk of strength degradation, especially in those specimens affected by brown rots.