Theoretical assessment of the limit strengthening criterion of strengthened bridge decks based on failure characteristics

The dominant failure modes of bridge deck are either flexure-shear or punching shear. Bridge decks strengthened with fiber reinforced polymers (FRPs) have an increased punching shear strength as well as improved flexural strength. This transforms the failure mode from biaxial bending to punching shear. Therefore, it is desirable to design the strengthened bridge deck so that it fails due to similar ductile behavior and with similar failure patterns as unstrengthened bridge decks, even though the ultimate strength of a strengthened deck with external reinforcements is much greater than its punching shear strength. For this reason, the concept of a strengthening limit criterion is introduced in this paper to ensure that strengthened decks have ductile dominant failure modes. The concept of failure mode transition, which is dependent on the amount of strengthening, is introduced in the practical design procedure, and a criterion for selecting the strengthening ratio is developed.