WOOD RESEARCH Volume 67, Number 4, 2022
Mario Núñez-Decap, Gustavo Pérez-Soto, Alexander Opazo-Vega, Boris Moya-Rojas, and Marcela Vidal-Vega

Study of wood adhesives on the bonding properties in solid and hollow glulam beams of Pinus radiata

The aim of this research was study of polyurethane (PUR), isocyanate polymer emulsions (EPI) and melamine-urea-formaldehyde (MUF) adhesives, on the bonding properties of solid and hollow glulam beams of Pinus radiata. The thermomechanical analysis (DMA) of the adhesives was carried out to evaluate their stiffness and reactivity. Glulam beams were evaluated by a bending test. The quality of the bonding was evaluated by resistance to shear and delamination. The morphology of the bonding was studied by microscopy. The DMA study showed that the MUF adhesive had the highest level of stiffness and reactivity. The results of the bending test showed that the highest modulus of rupture results were obtained in solid and hollow laminated beams with MUF adhesive, achieving increases of 30% over the PUR adhesive. The lowest delamination results were obtained in solid glulam beams with MUF and EPI adhesives, while the highest results were 32% and 47% for the PUR adhesive. Finally, glulam beams manufactured with MUF adhesive presented the best performance and results.

WOOD RESEARCH Volume 66, Number 6, 2021
Yifan Liu, Ziyin Yao, Feibin Wang, Hui Huang, and Zeli Que

Effect of edge distances on stiffness of shear-tension mode in glulam connections with inclined screws

The effects of edge distances on stiffness in glulam connections with inclined selftapping screws were studied in this paper. Under four anchorage angles (A-45°, A-60°, A-75°, A-90°) and three edge distances (EG-2D, EG-4D, EG-6D) conditions, the shear-tension tests were carried out on the timber structure connections with inclined self-tapping screws, and the stiffness and other properties of the connections were tested. Based on the results, the effects of edge distances on stiffness in joints were quantified using the equivalent energy elastic-plastic (EEEP) model. The results showed that the edge distances had a certain impact on the yield mode and load-carrying performance of the joints. Within a certain range of variation, as the edge distance increased, the stiffness of the connections increased gradually, showing a positive correlation. The stiffness of specimen EG-2D is 4.41 kN·mm-1. The stiffness of specimen EG-4D is 10.04 kN·mm-1, which increases by 128% compared with the specimen EG-2D. The stiffness of specimen EG-6D is 12.08 kN·mm-1, which increases by 174% compared with the specimen EG-2D. However, the ductility coefficient, yielding load, and energy dissipating have no significant change. Within a reasonable edge distance, only ductile damage occurred.

WOOD RESEARCH Volume 61, Number 6, 2016
Bo-Han Xu, Yan-Hua Zhao, Jing-Hua Guo, and Ya-Xun Wang

Fracture toughnesses of interlaminar fracture of glued-laminated timber

Critical strain energy release rate GC and stress intensity factor KC are both defined as fracture toughness, and they can be converted to one another through an equivalent elastic modulus for wood fracture. Whereas the equivalent elastic modulus for interlaminar fracture toughness of glued-laminated timber (glulam) is kept unknown. This paper briefly presented Modes I and II interlaminar fracture toughnesses of glulam, which were obtained from double cantilever beam (DCB) and three-point bending end-notched flexure (3ENF) tests using finite element method (FEM). On the basis of Hankinson-type formula and equivalent elastic modulus of wood fracture, this study developed two empirical expressions to calculate the equivalent elastic moduli for Modes I and II interlaminar fracture of glulam.

WOOD RESEARCH Volume 61, Number 1, 2016
Ivan Glišović, Boško Stevanović, Marija Todorović, and Tijana Stevanović

Glulam beams externally reinforced with CFRP plates

An experimental program was undertaken to investigate the effectiveness of carbon fiber reinforced polymer (CFRP) plates as flexural reinforcement of glued laminated timber (glulam) beams. Beams with and without reinforcement were tested up to failure in a four-point bending configuration. A comparison between the flexural behaviuor of control unreinforced beams with reinforced beams is shown and discussed. The results demonstrated increase in strength, stiffness and ductility when CFRP plate is bonded at tension side of cross section. Research findings indicated that the use of proposed reinforcing solution improves utilization of the compression characteristics of timber. Based on the experimental observations, a theoretical model is developed to predict the ultimate moment capacity and bending stiffness of CFRP-reinforced glulam beams.

WOOD RESEARCH Volume 64, Number 6, 2019
Marija Todorović, Ivan Glišović, and Boško Stevanović

Experimental investigation of cracked end-notched glulam beams repaired with GFRP bars

In this paper, an experimental research on bending behaviour of end-notched glulam beams and their bending behaviour after repairing with glass fibre reinforced polymer (GFRP) bars is presented. Altogether five glulam beams (100 x 220 x 4000 mm) made of spruce timber classified in the strength class C22 were tested. Experiment showed that originally, the beams failed in a brittle manner due to crack opening and its propagation. Cracks in the notch details were a result of excessive tensile stresses perpendicular to grain and shear stresses. Repairing the beams with GFRP bars after their failure completely restored and notably improved their load carrying capacity (average increase of 194%). Failure mechanism after repair changed from the original brittle tensile failure to more ductile failure in bending for most beams, proving the successfulness of the intervention. This study gives an insight in rehabilitation and repair possibilities of existing structures using advanced materials like GFRP bars.