1 INTRODUCTION
Glued-in-rods represent a particular class of adhesively bonded joints for engineering applications, in which load is transmitted from one timber element to another by means of stiffer and more resistant linear elements (rods) through a layer of adhesive. Owing to the practicalities, it has become standard to employ threaded metallic rods in order to maximize mechanical interlock and not rely on the adhesion to the rod. Glued-in-rods are most commonly connected to timber using cold-curing 2K adhesives, typically either epoxies or polyurethanes.
Although very good mechanical behaviour is reported, use of the aforementioned adhesives requires some min/max temperatures for curing. Overcoming these limitations requires specific techniques, as for examples resistive heating and inductive heating. Inductive heating of the rods can quickly generate extreme temperatures, up to melting the metallic rods. Therefore a strict control mechanism is needed to avoid temperatures in a range where the adhesive is irremediably destroyed. Resistive heating allows a finer control of the temperature, since the basic physical law behind (basically thermal energy is proportional to the squared intensity of the electrical current).

1.1 Scope of the paper
Based upon the preliminary experiences gathered on resistive and inductive heating, experimental investigations were followed up.

1.1.1 Increase of specimen size
Firstly, the specimen size was significantly increased, from 30x30 mm² timber section to 120x120 mm², which comes closer to full scale applications. Increasing the sample size imposed significant adaptations on the experimental hardware, as increasing the inductor size up to a diameter of 140mm. However, even at this scale jump, both techniques proved to be actionable, leading to reliable accelerated curing.

1.1.2 The use of 2K adhesives
Secondly, resistive and inductive curing was now performed using 2K-adhesives. Using 2K-EPX and 2K-PUR was considered because these two classes of adhesives would cure even under normal temperature conditions. Another benefit of 2K adhesives is that accelerated curing could be limited to partial curing of the adhesive, e.g. to achieve some minimum handling strength. However, 2K adhesives are generally not formulated to be cured at high temperatures; they are particularly sensitive to sudden increases of temperature. Accordingly, significant effort had to be put into the identification of adequate epoxies, and polyurethanes, suitable for the intended application.

2 Discussion
2.1 Large-scale tests
The capacity of the adhesives to cure significantly faster was subsequently verified on the large scale GiR. Two methods were investigated: inductive and resistive heating. Both methods proved the validity of the concept of accelerate curing, as only slightly lower joint capacities were obtained for specimen tested 24h after their respective accelerated curing, if compared to “traditional” cold cured ones.
If testing probes before they could completely cool down, load capacity was in part lower. However, as shown in the tests, this was mostly due to the fact that the threaded bar still exhibited significant temperatures. The results, however, showed that significant handling strength was offered by the accelerated curing, which has the potential to ease the problematics of slow curing 2K adhesives in industrial processes.

3 Conclusions
Accelerated curing of commercially available and widely used 2K-epoxies and polyurethanes was investigated in the context of Glued-in-rods. Preliminary tests on the adhesives showed that all adhesives could be fully cured with significantly shorter times, to be counted in minutes rather than in hours or days. Subsequent validation thereof on large scale GiR proved the validity of the concept, as inductive heating allowed to cure 120x120 mm² sections of beech LVL within 5 minutes, and resistive heating within one hour. Resulting joint capacities proved comparable in strength, if tested after complete cool down.