Investigation of stress perpendicular to grain and cracking of curved glulam beams

A comparative study between the stress perpendicular to grain of curved glulam beams and radial stress of curved beams made of isotropic material was conducted. The distribution of stress is generally similar with each other. But the stress perpendicular to grain in Glulam distributes in a saw-toothed pattern and is affected severely by the position of the pith in a lamina. The maximum stress perpendicular to grain is reached when the pith appears on the wider face of lamina and it is 1. 5 times the result by the simplified formula. Based on the characteristics of stress perpendicular to grain and the fact of brittle fracture, an elastic-brittle damage constitutive model for predicting cracking of glulam was developed. The constitutive model consisting of the damage model and failure criteria was incorporated into the commercial FE software ABAQUS by developing a user defined subroutine-UMAT. Then FE models were developed to predict the cracking and load-carrying capacity of curved glulam beams. The load-carrying capacity and stiffness of numerical simulation are correlated well with the experimental results.