Jointing tubular FRP components for planar and space grid structure constructions

Fibre reinforced polymer (FRP) materials have demonstrated their advantages in various applications for the rehabilitation and repair of existing concrete and steel structures because of their light weight and high strength and excellent corrosion resistance. With the help of the pultrusion process, tubular shapes made using FRP composites provide similar sectional geometries to steel profiles. This paper explores the potential of tubular FRP profiles as construction members to form planar and space grid structures. In such structures, the structural members are interconnected at a space node transferring loads axially, where tubular FRP profiles exhibit their best material strength. An innovative joint configuration is developed in this paper to connect circular FRP tubes for planar and space grid structures. The concept here is to incorporate a tubular steel connector into the FRP member through adhesive bonding at one end and the other end of the steel connector is flattened, enabling its simple connection with other structural members using mechanical bolts. With the help of a novel joint connector, such GFRP components were assembled into two space truss units which were then tested statically. During the experiments, the load-displacement responses were recorded. For the first structural unit, failure occurred at the low chord joints in a ductile manner, because of the premature separation of the joint connector. The joint connector was therefore adhesively bonded into one piece in the second structural unit, and this modification demonstrated a significant improvement of load-carrying capacity. Further improvement of joint capacity is expected through the improvement of bonding quality or the integrated manufacture of the joint connector.