Strain Rate Effect on the Embedment Mechanical Properties and Fracture Behavior of Softwood Laminated Veneer Lumbers: Implications to Timber Connections

Abstract

This paper experimentally investigates the influence of the strain rate experienced during earthquake and progressive collapse events on mechanical properties affecting the design of softwood laminated veneer lumber timber connections. The parallel and perpendicular to grain embedment stiffness and strength, tension strength perpendicular to grain, and Mode I and II fracture energies were examined under four levels of strain rates. Results showed that the embedment stiffness and strength increased by up to 35% from the quasi-static to dynamic strain rates, whereas the embedment ductility decreased by up to 17%. The fracture energies and tension strength perpendicular to grain were found to be mostly insensitive to the investigated range of strain rates. Furthermore, the influence of the strain rate on the behavior of timber connections is analyzed and discussed by (1) using the experimental data in the European standard design equations for single and double shear connections; and (2) quasi-statically and dynamically testing one connection type with two different fastener spacings. Results showed that for the connections investigated, the dynamic strength can be up to 30% higher than the quasi-static one, however, the dynamic ductility of the connections can be reduced substantially by up to 32.5%.