WOOD RESEARCH Volume 69, Number 4, 2024
MARIJA TODOROVIĆ, IVAN GLIŠOVIĆ, and NAĐA SIMOVIĆ

EXPERIMENTAL AND NUMERICAL INVESTIGATION OF CLT PANELS WITH DIFFERENT ORIENTATIONS OF TRANSVERSE LAYERS

This paper presents an experimental and numerical investigation of two configurations of panels made of locally produced cross-laminated timber (CLT) with different orientations of laminations (boards) within transverse layers – conventional and modified orientation. Modified orientation refers to laminations of transverse layers positioned at an angle of ±45° in relation to longitudinal layers. The expected advantages of modified CLT are improved mechanical performance, more efficient use of resources considering material properties, reduction in variability of characteristics within the panels and increase in shear resistance. In addition to experimental testing, numerical analysis based on finite element method was performed and successfully validated in order to serve as a more efficient tool for CLT panel investigation and optimization

WOOD RESEARCH Volume 68, Number 2, 2023
MARIJA TODOROVIĆ, Mathieu Koetsier, NAĐA SIMOVIĆ, IVAN GLIŠOVIĆ, and Marko Pavlović

Determination of mode I fracture properties of European spruce

In this paper an efficient procedure for obtaining a cohesive law for Mode I timber fracture (crack opening), based on the Double Cantilever Beam (DCB) tests is given. DCB tests were performed on ten European spruce specimens in order to determine the energy release rate vs crack length (R curves). Two crucial parameters – crack length during the experiment and the crack tip opening displacement were obtained using 2D Digital Image Correlation (DIC) technique. In order to determine accurate fracture resistance (R curve), procedure which includes calculating cumulative released energy was employed. The cohesive law for Mode I fracture of wood was obtained by differentiation of the strain energy release rate as a function of the crack tip opening displacement. This cohesive law is further implemented in the successful numerical modelling of failure modes in large-scale end-notched glulam beams which were experimentally tested in four-point bending configuration.

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.