Experimental and numerical investigations of pull-out strength of timber joints with glued-in rods

Abstract

Timber joints with glued-in rods have several advantages with respect to mechanical connections, such as higher stiffness, more uniform stress distribution, less bar corrosion problems and better appearance. This thesis describes experimental and numerical studies of timber joints made with glass fibre reinforced polymer (GFRP) rods glued by polyurethane adhesive (PUR) into glued-laminated timber specimens made of Douglas-fir. Experimental work was performed at Centre for Advanced Wood Processing of the Wood Science Department and the Materials Laboratory of the Civil Engineering Department at University of British Columbia Vancouver. A total of 125 specimens from 25 different test series with 5 replicates each were tested in tension until failure. The objective of the study was to evaluate the influence of the geometric parameters on the joint performance. The experimental data showed the importance of the rod diameter and anchorage length on the capacity of glued-in rod joints. In all the cases, when increasing the diameter of the bar or anchorage length, the average value of the reached failure load increased; this increase, however, was not linearly proportional to the timber-adhesive interface. Experimental failure loads have been compared with the theoretical values and in all the cases the experimental results were lower than the theoretical values, which might be because of incompatibilities between the chosen PUR and GRFP rod. A 3D finite element model was developed using the commercial software package ANSYS 14.0 in order to investigate the stress distribution within the joints. The model was validated and found to be in good agreement with the experimental observations, allowing it to be used for future parameter optimization and the application of numerical capacity prediction methods.