Modeling of through-thickness stress state in adhesive joints connecting pultruded FRP bridge decks and steel girders

The through-thickness performance of adhesive joints connecting pultruded FRP bridge decks and steel girders subjected to loading in the transverse bridge direction was investigated. Deck-to-girder adhesive joints can be assumed as being loaded by uplift forces only (and not by additional bending moments) if the adhesive layer has a minimal thickness of approximately 10 mm. If possible, however, steel web stiffeners should not be connected to the upper flange in order to allow free flange rotation. The tensile stress distribution in the adhesive joint is non-uniform with high stress concentrations below the FRP webs of the cellular deck and above the steel girder web. Alternately inclined deck webs cause significantly higher stresses below the vertical webs. An analytical model allowing the calculation of a representative approximation of the complex uplift stress state in the joint is proposed and validated by numerical and experimental results. Based on this model, a design method for adhesive joints connecting FRP decks and steel main girders can be established.