Openings are usually required to allow services like plumbing, sewage pipes and electrical
wiring to run through beams. This prevents an extra depth of the floor/ceiling, while preserving architectural considerations. The introduction of large opening causes additional tension perpendicular to grain in timber beams. The low tensile strength perpendicular to grain of wood allows crack formation. Crack propagation around the hole considerably decreases the load-carrying capacity of the beam. However, in most cases, crack formation and propagation around
the hole can be prevented by the use of an appropriate reinforcement. Screw, glued-in rods, and plywood are alternative options for the reinforcement. Design of the reinforcement requires that the working mechanism of the reinforcement is fully understood and properly addressed. In addition, reinforcement should be designed for actions produced in the section of the beam weakened by the hole. The current paper uses a simple truss model around the opening to calculate the tensile force in the reinforcement. Two simple formulations for design of the reinforcement are derived and compared with numerical and experimental results, showing an overall good correspondence. The proposed truss model can be considered for incorporation in future codes of practice.
Glued-in rods (GiR) are an effective way to connect timber elements from both load bearing capacity/stiffness and aesthetic point of view. This method is also widely accepted as a method for reinforcement of the new and existing timber structures. Although GiR are widely used in timber structures, there is still no unified European test standards, product standards or design equations for such connections. At present, there are several test methods and procedures applied in research and development. In this paper two different methods for obtaining pull-out strength are presented. Furthermore, experimental investigation was conducted and results obtained from both methods are mutually compared. Pull – compression test procedure is the most common setup for experimental investigation, however this setup is sometimes not representative and it is often characterized as unreliable because it does not quite good correspond to practical applications. The second examined test procedure was pull-pull. Within the experimental investigation, total number of 36 specimens were tested and results obtained from both methods are shown, discussed and compared in this paper.
This paper describes the test program of glued-in deformed bar timber joint conducted in pull-pull configuration, which aims to investigate the bond behavior of glued-in deformed bar systems in glulam. The varying parameter are bar slenderness ratio and glue-line thickness. In order to obtain the bond stress distribution along the anchorage length, special deformed bar with strain gauges attached internally were designed. Test results show that both the bar slenderness ratio and glue-line thickness have obvious influence on withdrawal strength and bond behavior of glued-in deformed bar joint. Failure modes of specimens are also analyzed in this paper. Ductile failure modes of glued-in rod timber joint could be realized with reasonable design.
The application of cross-laminated timber (CLT) as floor panels is limited by excessive deflection and vibration. A composite system combining CLT and ultra high-performance fibre-reinforced concrete (UHPFRC) was developed to extend span limits. Push-off tests were conducted on different connectors, and a glued-in rod connector was chosen and further refined for the proposed system. Static bending tests and free vibration tests were conducted on bare CLT panels and two composite specimens. By comparing the results, it is concluded that the proposed system considerably extend the span limits of CLT panels.
In order to explore bamboo glulam utilization in structure construction, the adhesive bonded steel connection of bamboo glulam was investigated in this study. By carrying out both-end pullout tests on glued-in threaded rods in bamboo glulam, the effects of depth and diameter of embedded rods in bamboo glulam on the pullout strength and the failure modes were discussed. Results showed that threaded rods fracture and adhesive interface failure were the two main different failure modes in the tests. The pullout peak load of both-end glued-in rods in bamboo glulam increased with the diameter and the embedded length of the threaded rods. To satisfy tensile load of the glued threaded rods (quality 4.8) used in the connections between engineering structural materials, the slenderness ratio ( , the ratio of depth and diameter of glued-in threaded rods) equal to 10 or over was necessary.
This paper uses finite element analysis (FEA) to verify the results of previous experimental works conducted on the effect of glue-line thickness and rate of loading on pull-out behavior of glued-in GFRP rods in LVL. For this purpose, the materials were considered as orthotropic for the timber and the GFRP rod, and isotropic for epoxy resin. To determine the effects of thickness on pull-out, four glue-lines namely 0.5, 1, 2 and 4 mm were modelled. To examine the effects of rate of loading, three glue-lines 0.5, 2 and 4 mm were modelled with different values of modulus of elasticity selected for the resin to simulate higher and lower rates of loading. Results showed that with an increasing thickness of glue-line, the concentration of Z-direction stresses declines across the glue-line thickness from the rod-adhesive interface towards the adhesive-timber interface and the magnitude of shear stresses, tXZ, increases to a maximum within the glue-line in a zone about 20e30% into the resin layer and this is seen for all glueline thicknesses. Also, by changing values of elastic modulus for the resin in the FE model to simulate rate of loading, it was shown that thicker glue-lines are more sensitive to loading rate