Experimental analysis on a T-shaped metallic profile connection between main and secondary beams

Connecting timber elements has always been a difficult task, regarding both design and construction methods; the innovation in construction products and of the CNC machine has led to the optimization of performance and the time procedures of connection systems. Through this kind of connection it is possible to join the secondary beam in the depth of the main beam. With T-shaped metallic profile with a height of 200-300 mm, it is possible to adopt this system for loads and spans typical of residential buildings. Heavy timber structures, typical of industrial hangers, require higher profiles. Inserting the steel profile into the wood by means of grooves can take many advantages in term of fire resistance (the metal parts of the joints are "protected" by the wood, which bums slowly and insulates for the heat transmission), in terms of the possibility to speed up and to facilitate the assembly phase, and also in terms of aesthetic appearance. In this paper the results of experimental procedures carried out on T-shaped metallic profile joints are illustrated. The goal is to investigate ultimate behaviour of the joint. To this purpose, two specific test set-ups have been designed: asymmetric push-out tests, where the load is applied directly to the steel web of the T-shaped metallic profile and where the metallic flange is nailed to a wooden block; symmetric test arrangement, with a timber secondary beam spanning 2 meters, laterally supported by means of the T-shaped metallic profile connected to two transversal timber beams. The profile flange is nailed to the main beam, and the profile web is connected with dowels to the secondary beam. Different geometries of the joint have been tested, ranging the height from 120 mm to 360 mm (30 specimens for the first set-up, 12 specimens for the second set-up). The experimental results illustrate the static performance of the connection system, in terms of both resistance and ductility, thank to the high number of small diameter connectors.