M. Khelifa

Analysis of CFRP-strengthened timber beams

The aim of this study is to develop a numerical procedure to simulate the flexural behaviour of carbon fibre-reinforced plastic-strengthened timber beams. Since wood exhibits complex failure modes, its behaviour can only be captured through the use of multidimensional failure criteria, a local approach based on the coupling of orthotropic elasticity and anisotropic plasticity described with the quadratic criterion of Hill is presented to model this behaviour. The theoretical and numerical aspects of the constitutive equations are presented in detail. The resolution of the resulting system of equations is carried out via a VUMAT user material, using ABAQUS/Explicit finite element code. The obtained results show that the proposed formulation can efficiently capture the global response with acceptable accuracy.

Flexural strengthening of finger-jointed Spruce timber beams with CFRP

This study describes an experimental and numerical investigation of the use of CFRP material for strengthening finger-jointed Spruce timber beams. The corresponding experimental work was based on a four-point bending test configuration in order to characterise stiffness, ductility and strength. The results show that the external bonding of CFRP increased the ultimate load-bearing capacity of finger-jointed Spruce timber beams under flexure. FE simulations were also carried out, based on the cohesive zone model (CZM) available in Abaqus software to allow an accurate description of the damage evolution of the bond lines within the finger joint until failure. The FE models incorporated the different materials’ nonlinear constitutive laws including bond-slip action between finger joints and CFRP–timber interface. The results indicated increases of 33.84% and 16.7% for flexural capacity and initial stiffness, respectively, in comparison with unreinforced finger-jointed Spruce specimens. Besides, comparisons of computed and experimental ultimate loads for all tested specimens showed that the absolute error was around 5%. It is concluded that the developed FE models are able to predict accurately ultimate load and failure mode of finger-jointed Spruce timber beams strengthened with CFRP materials.

FE simulation of repaired timber beams under tensile load using CFRP patches

Timber is a highly orthotropic material with highest strength presented in tension along the grain direction. Repaired timber structural elements in pure tension using carbon fibre–epoxy patches provide new opportunities as it is well adapted to the nature of wood. Such repairing process is very interesting as it is easy to use for assembling two damaged parts of timber and has a low environmental impact. Before this process can become widespread in the industry, it is necessary to develop numerical tools for predicting the behaviour of such assemblies under tensile loads. Only a few experimental tests have been offered in the literature, and even fewer numerical studies have been carried out to analyse the complex mechanical behaviour of timber. The present paper describes the use of carbon fibre–epoxy patches for repairing timber beams under tensile stress along the grain direction. The repaired beams with CFRP patches using varying repair lengths were examined. The load-carrying capacity increased by about 47%, passing from a repair length of 5 mm (F = 3.8 kN) to a repair length of 10 mm (F = 6.6 kN) at a displacement u = 0.3 mm. A three-dimensional (3-D) numerical methodology for virtual loading process under pure tension, including the interaction between two adherent surfaces and taking the presence of an adhesive layer into account, is presented from both theoretical and numerical point of views. Predicted and measured load–displacement responses and failure modes are compared. The predicted results are in good agreement with the experimentally measured test data.

FE Analysis of Flexural Behavior of Externally Bonded CFRP Reinforced Timber Beams

This study focuses on the flexural behavior of timber beams externally reinforced using Carbon Fibre Reinforced Plastics (CFRP). A non-linear finite element analysis is proposed in order to complete the experimental analysis of the flexural behavior of the beams. An elasto-plastic behavior is assumed for reinforced Timber and interface elements are used to model the interaction between CFRP and timber.The predicted and measured load–midspan deflection response results in addition to the failure modes are compared. It was observed that the predicted FE results are in good agreement with the experimental measured test data.

Numerical Analysis of Laminated Veneer Lumber Panels in Fire

This paper presents models for calculating the fire behavior of Laminated Veneer Lumber (LVL) elements. A 2D FE thermal model was employed to analyze heat transfer within LVL panels. The thermal model was found to provide good predictions when comparing the calculated temperatures and residual cross-section dimensions of LVL panels with the experiment results.