Extended finite element analysis on size effects of bending performance for Chinese larch pine laminated veneer lumber

Laminated Veneer Lumber (LVL), known for its excellent physical and mechanical properties, is widely used as flexural members in modern timber structures. This study aims to numerically investigate the size effect on the bending performance of LVL and provide a foundation for the engineering design of such members. Using Chinese larch pine LVL (CLP-LVL) as a case study, material properties obtained from tests were adopted to construct the bending model through Extended Finite Element Method (XFEM) and Cohesive Zone Model (CZM) method. The model incorporated equivalent cracks to characterize the depth and width effects on the bending performance of CLP-LVL. The results indicated that the XFEM and CZM method could effectively simulate the load-displacement relationship, bending strength, and failure modes of CLP-LVL. The XFEM crack was proved to be an effective approach for modeling strength degradation defects in CLP-LVL. Parameters for the equivalent cracks representing the depth and width effects on bending performance of CLP-LVL were derived, and a numerical analysis method for its size effects based on equivalent crack was proposed. It is recommended to introduce a 30 degrees equivalent crack in the bending model of CLP-LVL, as the resulting load-displacement relationship, bending strength, initial crack, and delamination are in strong agreement with experimental results for full-scale CLP-LVL. The proposed numerical method is also applicable for analyzing the size effect in other timber flexural members with similar material properties to CLP-LVL. For other brittle materials or members, parametric analysis of equivalent cracks can be employed in the related model to propose corresponding numerical methods for analyzing bending size effects.