Analytical and experimental study on bonded-in CFRP bars in glulam timber

The application of fiber-reinforced polymer (FRP) composites to glue-laminated timber members, although the object of limited investigations to date, offers a good potential for both strengthening and new construction. In particular, the possibility of using FRP rods as connections for glulam timber elements in place of steel is of interest, due to the improved durability of the system and to the easier and faster application guaranteed by the lightweight properties of FRP materials. In this study, pull-out tests were conducted to study the bond performance of FRP rods epoxied into glulam elements. The test variables were bonded length, surface configuration of the rod and direction of the wood fibers with respect to the longitudinal axis of the joint. Based on the experimental curves, the local bond-slip behavior of the joint was modelled and used to obtain numerically the ultimate load of the joint as a function of the embedment length of the bar. Also, the behavior of the joint in the plane perpendicular to the axis of the bar was modelled for the cases of bar parallel and perpendicular to the grain, showing that splitting bond failure is more critical for bars parallel to the grain, as observed experimentally.