Strengthening crack bridging

The flexure bar subjected to 1200°C under an applied stress of 200 MPa failed after 58 hours. The failure was completely brittle, since there was no fiber-pull out and the crack propagated in a perpendicular manner through the entire bar. This brittle failure indicates that at this temperature there is a strengthening of the fiber/matrix bond which reduces the likelihood of fiber pull-out or crack bridging as possible toughening/strengthening mechanisms. 

Two bridges on the M20 in Kent were strengthened shortly after construction in 1977. Cracks were discovered in one of the side spans which were found to have insufficient longitudinal steel. Steel plates were subsequently bonded to the side span soffits and the top surface of the deck over the supports (Fig. 6.9). 

A recent example of a bridge strengthening scheme in this country is the upgrading of a pedestrian bridge at a service station on the M2 in Kent. After design checks revealed that there was insufficient steel in the deck and a bridge inspection showed that there were transverse cracks in the soffit, longitudinal plates were applied to... 

Teng, J. G., Lu, X. Z., Ye, L. P. and Jiang, J. J. (2004), Recent research on intermediate crack de-bonding in FRP-strengthened RC beams . Proceedings of 4th International Conference on Advanced Composite Materials in Bridges and Structures (ACMBS IV), Calgary, Alberta, Canada, July 2004 (CD-ROM). 

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