First investigation on mixed cracks and failure modes in multi-bolted FRP plates

Abstract

The research analyzes the failure modes in pultruded FRP (fiber reinforced polymer), plates used in structural connections, with a large number of holes for bolting and subject to in plane stress. The study is part of a context in which the strength’s verifications and modes of failure in all-FRP nodes joined with angle and with a limited number of holes are well known, while the literature is lacking in the presence of FRP plates with a large number of bolts. The survey provides an initial experimental analysis of the possible crisis mechanisms, taking into account the recent findings related to the behavior of all FRP beam-column joints, to the orthotropy of the material and to the effect of the holes. This experimental based approach is then compared with the Withney-Nuismer model on assessing the effect of the holes in orthotropic plates with respect to the determination of the strength values. The comparison regards also the criterion of Strain Energy Density on the trigger and the propagation of the crack phenomenon. The study concludes with an analysis of the new cracks and mixed modes of failure with respect to cracks and modes of crisis already known in the literature.