High prestressing of externally mounted CFRP plates for prestressed hollow-core slabs strengthening

Strengthening concrete structures with externally prestressed carbon fiber reinforcement polymer (CFRP) plates has been proven to be an effective method to improve their serviceability and the ultimate performance. However, it has not been widely used in the field due to the challenges associated with the high prestressing levels and anchoring techniques. This paper presents an experimental investigation of the flexural behaviour of full-scale prestressed hollow-core slabs (PHCS) strengthened with externally bonded and unbonded prestressed CFRP plates under high prestressing levels, up to 72 % of the CFRP plate’s tensile strength, utilizing a novel field-applicable wedge anchorage system. Results indicated that strengthening with high prestressing levels led to an efficient use of the CFRP material and better utilization of its high tensile strength. The ultimate and cracking loads were increased by as much as 48.8 % and 25 %, respectively, for the strengthened slabs compared to the control slab. In addition, a significant enhancement by up to 145 % in ductility was observed for the slab strengthened at high prestressing levels compared to the control slab.