Advances in adhesive joining of carbon fibre/polymer composites to steel members for repair and rehabilitation of bridge structures

Generally, it is relatively easy to obtain a high joint strength with most modern bonding systems if these are cured under ideal factory conditions. However, civil engineering construction joints are cured on site and are required to last the lifetime of the structural member in harsh environmental conditions. This implies that site joints might not be constructed and cured as well as those fabricated in the factory. The paper compares two possible methods for bonding an FRP composite patch/plate to a steel adherend suitable for construction sites. The first method utilises the accepted technique of bonding two dissimilar materials using a two-part cold cure adhesive. The second method employs a pre-impregnated FRP composite plate in conjunction with a compatible film adhesive; these comparisons are undertaken by examining the results of double-strap butt joint tests. A possible site technique using the pre-impregnated FRP composite to upgrade a steel beam whilst it is under a low frequency vibration load is investigated; this represents the repair of a steel bridge constantly under traversing traffic. The butt joint test results show that on average, the pre-impregnated composite in conjunction with the film adhesive leads to a failure load which is 15% higher than that of the cold setting adhesive technique. The results of the rehabilitated beam tests show that the bonded joint between the pre-impregnated CFRP composite and the steel adherend did not suffer any significant damage from the low frequency vibrations imposed upon the steel beam during the cure period.