Beam-Column connection for FRP structures

The use of FRP profiles is appropriate and advantageous for construction of industrial and low-rise residential buildings as well as temporary structures built in emergency situations. But for FRP composite structures to be competitive with structures made of traditional materials, they must be safe, serviceable, durable and economical. Structural safety and serviceability depend on the structural members’, as well as on their joints’ or connections’, strength and stiffness. Currently, the connections in FRP structures are commonly made using bolted connections [1-2], akin to those used in steel structures while, as stipulated in a recent European guideline [3], bonded connections are not allowed for primary load bearing components. Figure 1. a) Connection tested in [4], b) new connection. With respect to bonded beam-to-column moment resisting connections, the authors in a recent paper [4] demonstrated that this prohibition appears to be unjustified. An identical pultruded GFRP I-profile was used to form the beam and the column elements. The two elements were connected by epoxy adhesive, and GFRP seat angles, bonded to the column compression flange and the beam tension and compression flanges. In addition, stiffeners were used in the connection region to strengthen the column flange and web. The beam, acting as a cantilever, was loaded by a point load near its free end, which subjected the connection to combined bending and shear. The connection (Figure 1a) failed by debonding within the adhesive, achieving nearly the same percentage of the GFRP profile ultimate moment capacity as in the best performing bolted connections tested by others. As a follow up to the previous work, in order to further enhance the forgoing connection strength and stiffness, in this study the column and the seating angle bonded to the beam tension face and the column are strapped together using a carbon wrap as depicted in Figure 2b. The new connection is loaded identically to the previously tested connection, and, compared to the companion unwrapped connection, the results of the improved connection show increase in both the ultimate moment resistance and rotational stiffness. This improvement makes adhesive connections an even more appealing choice for practical applications. [1] L.C. Bank, A.S. Mosallam, G.T. McCoy, Journal of Reinforced Plastics and Composites, 15, 1052 (1994). [2] S.J. Smith, I.D. Parsons, K.D. Hjelmstad, Journal of Composite for Construction, 3, 20 (1999). [3] Report EUR 27666 EN, Prospect for new guidance in the design of FRP. JRC Science for Policy Report, 2016. [4] F. Ascione, M. Lamberti, A.G. Razaqpur, S. Spadea, S., J. Comp. Struct., 160, 1248 (2017).