Improvement of Serviceability by Strengthening with Prestressed NSM

Carbon fibre reinforced polymers (CFRP) are often used for strengthening. In most applications the CFRP-reinforcements are externally bonded (EBR) to the structure. An improvement can be achieved by near surface mounted CFRP (NSM), due to the better bond behaviour. Further improvements can be obtained by prestressing, for example: utilization of the high strength, activation of dead loads and much lower deflections, without losing ductility by approaching the ultimate load (if appropriately designed). The advantage of a delayed cracking of concrete and yielding of the steel reinforcement leads to lower crack widths, higher durability and an increase in the serviceability load. Durability is further enhanced by the “bond anchorage”, where no corrosive materials are applied to the structure.