Design of robust and ductile FRP structures incorporating ductile adhesive joints

A design concept for engineering structures consisting of brittle FRP components and ductile adhesive joints is proposed. The elastoplastic adhesive joints provide system ductility that compensates for the material ductility that FRP composites lack. In the elastic phase, the adhesive offers sufficient stiffness to provide continuity of stiffness over the joint, thus meeting the short- and long-term serviceability requirements for the structure. In the plastic phase, the adhesive develops a uniform stress distribution along the overlap length, thereby enabling sufficient joint rotation to provide an internal force redistribution that increases structural safety and robustness. The application of the design concept to a two-span FRP beam system with an elastoplastic hinge at mid-support showed an increase in structural robustness of almost 140% compared to a continuous FRP beam. FRP structures designed according to the proposed concept exhibit much higher structural safety than brittle structures without force-redistribution capacity.