Author(s)

G Wight, P Bouffard, M A Erki & R El Hacha

Abstract

There is an economy of design and redundancy inherent in continuous multiple-span concrete bridges. In zones of conflict, bridges are prime targets. If a span in a continuous bridge is severely damaged due to blast or impact loading, there will be a loss of continuity, and the positive bending moments of the remaining spans may become much greater than accounted for in the original design. So while the damaged span may be over-bridged using a modular, prefabricated bridge, the remaining spans, even if they carry reduced traffic loads, can deteriorate so severely as to no longer be serviceable. This paper summarises investigations into the behaviour and strengthening of components in severely damaged continuous, multiple-span structures. The testing program consisted of sixteen two-span, 8 m long reinforced and prestressed concrete beams that were constructed and tested, The beams were damaged by blast loading using explosives, mechanical cutting or impact loading with a hydraulic actuator applied to one of the two spans, which caused collateral damage in the second span. Three beams were used as undamaged controls, and six served as damaged control specimens. The remaining beams were damaged and strengthened using various flexural strengthening systems and were tested to an ultimate failure condition. Most specimens were strengthened with harped external prestressed steel wire. Others were strengthened with externally bonded prestressed and non-prestressed Fibre Reinforced Polymer (FRP) sheets. It was found that the external reinforcement effectively restored strength and stiffness to the damaged girders and that numerical models could accurately predict the behaviour of the damaged and strengthened structures.

Keywords