Behavior and Damage Characterization of Impulsively Loaded Cross-Laminated Timber Panels

This research bridges the gap between the quasi-static and high-strain-rate loading regimes in cross-laminated timber (CLT) by investigating two areas that have remained unstudied or elusive, i.e., rolling shear failure of CLT under impulsive, blast-like loading and intermediate strain rates in CLT. To study the conditions that would promote shear modes of failure, a novel, highly adaptable center-point testing system and methodology were developed that permitted the application of impulsive loading to undamaged CLT panels in a highly controlled and repeatable manner. The loading condition and low span-to-depth ratio (6.40 ≤ L:h ≤ 6.55) CLT were selected to encourage the development of shear modes of failure. Changes to the rotational rigidity at the boundary conditions allowed for the empirical simulation of realistic boundary conditions. Digital Image Correlation (DIC) and load cell data were used to identify failure modes following loss in resistance in the specimens. Overall, the experiment was successful in consistently eliciting shear modes of failure and providing damage characterization in impulsively loaded CLT. Shear modes of failure resulted in the dramatic loss of resistance in all specimens tested. Strain-rate enhancement in the dynamic apparent flexural stiffness of CLT of 1.3 to 7.2 times was observed. Lower levels of damage were observed in specimens with higher levels of boundary-condition rotational rigidity.