Maillart bridge: from structural concept to strengthening

This paper presents an innovative strengthening concept for open-spandrel reinforced concrete deck-stiffened arch bridges, known as ‘Maillart bridges’ all over the world. The strengthening concept and design equations are presented for a real bridge of span length 60 m built in southern Italy in 1965. Theoretical concepts related to the mechanical behaviour of the bridge are presented using traditional structural analysis based on the influence line theory. This paper shows how such a method can easily highlight the parameters necessary to define a strengthening strategy that should preserve architectural aspects of a bridge. To meet the new load-bearing capacity derived from new traffic needs, the arch strength should be increased by 17% while the shear and flexural strength of the deck should be increased by 35%. The strengthening concept involves increasing the arch thickness by 5% by using fibre-reinforced concrete (which will also improve the durability of the structure), increasing the flexural strength of the deck with the use of unidirectional fibre reinforced polymer epoxy-bonded laminates and increasing the local shear strength of the deck with bidirectional epoxy-bonded sheets.