Finite-element-based concept to predict stiffness, strength, and failure of wood composite I-joist beams under various loads and climatic conditions

Abstract

Formwork support constructions are an indispensable part of almost all reinforced concrete structures. The main supporting system usually consists of wood-based composites, where solid timber, plywood and, more recently, aluminum profiles are combined to form I-beams. These beams have to go through a very complex test program, to ensure that they withstand all mechanical and moisture-related stresses during their service life. To better understand the mechanisms leading to mechanical failure as well as to support a targeted optimization of new cross section types, we developed a finite-element-based simulation concept. Moisture-related effects occurring during the service life are considered with an advanced moisture transport model and a multisurface failure criterion is implemented for modeling the plastic and brittle failure mechanisms in wood, resulting in a very good prediction of stiffness values, load-carrying capacities and failure behavior of the experimentally investigated beams. The performance of the modeling approach is shown by simulation of three different experiments, representing different mechanical loading situations at three different moisture levels.