Pilot study on the experimental behavior of GFRP-steel slip-critical connections

It is well known that Pultruded Fiber Reinforced Polymers joints suffer from the problem of transfer of high shear loads with bolted connections due to the low pin-bearing resistance of the material and to the elastic-brittle behavior which does not allow significant plastic redistribution of stresses between the different bolt rows. In order to overcome these issues, in this paper, the possibility to realize slip-critical connections with steel and PFRP plates is examined. Slip-critical connections, currently, are not allowed by national and international codes dealing with pultruded structures also due to the limited knowledge that has been achieved up to now by the scientific community. In fact, till now, few experiences are available and they only regard friction connections with all-PFRP elements. In order to try to fill this knowledge gap, in this work, experimental tests on specimens with a layout analogous to that proposed by EN 1090-2, but realized with mild-steel plates and PFRP plates extracted from web and flanges of a structural profile, are carried out. The experimental results are commented, presenting the main outcomes, essentially with the aim to retrieve the design value of the friction coefficient for steel on PFRP friction interfaces.