Influence of high strain-rates on the dynamic flexural material properties of spruce–pine–fir wood studs

Abstract

The influence of high strain-rate loading on the flexural response of typical light-frame wood construction has been investigated. A total of 30 stud grade 38 mm × 140 mm × 2440 mm (2″ × 6″ × 8′) spruce–pine–fir (S–P–F) lumber specimens were tested within a range of low and high strain-rates between 6 × 10−6 s−1 and 0.4 s−1. A single-degree-of-freedom iterative solution procedure was used to compute the high strain-rate modulus of rupture (MOR) and modulus of elasticity (MOE). The MOR was statistically enhanced by high strain-rates, while the MOE and strain at rupture were not. Since equilibrium of the dynamic stress–strain relationship requires that one or both of the MOE and strain at rupture must be sensitive to strain-rate effects, the lack of observed rate enhancement on these material properties was attributed to large scatter within a small sample set. Based on the results, material dynamic increase factors and a stress–strain relationship suitable for blast resistant design of timber structures were also proposed.