Integrating energy transferability into the connection-detail of coastal bridges using reinforced interfacial epoxy-polyurea reaction matrix composite

Abstract

A new Carbon-fiber Interfacial Epoxy-Polyurea Matrix (C-IEPM) composite is investigated as a potential retrofit option for vulnerable girder-to-cap connection-details in coastal highway bridges. IEPM is a reaction of cross-linking epoxy with functional groups of pre-polymerized polyurea, producing an energy-transfer mechanism inherently absent in conventional carbon-fiber reinforced epoxy (CF/E) that drastically reduces the serviceability limit state during extreme hurricane events. IEPM is a covalently bonded interface, produced as a reaction of migrating epoxy species (epoxide and amine-based hardener), controlled as a function of their curing time (tc), with highly reactive isocyanate and amine polyurea moieties. To demonstrate IEPM effectiveness, six scaled concrete girders were tested using a modified simulated storm surge and slamming wave force function, derived using regional maps for a 100-year return-period Hurricane Katrina. Two girders, designed using current AASHTO field connection-details, failed catastrophically (concrete shear failure) in less than one-half load cycle. The CF/E-strengthened girder, failing in less than one load cycle, experienced severe damage to its girder-to-cap connection, including fiber and epoxy matrix breakage, delamination, unsustainable girder-end rotations, and transient force-displacement hystereses loops. However, after 12 load cycles, the C-IEPM-strengthened girder, providing substantial energy transferability (material damping) through its connection-details, experienced only local cracking.