Strengthening of precast prestressed hollow core slabs with CFRP sheets

Precast prestressed hollow core slabs are very commonly used as floor system in Saudi Arabia in the booming precast concrete construction industry. Strengthening of these slabs may be required for several reasons including increased load due to higher dead or live loads, architectural modifications in locations of walls, damage due to corrosion, installation of heavy machinery, opening cut through slabs and errors in planning, construction and design. This paper presents the results of flexural strengthening of hollow core slabs using CFRP sheets. Seven full-scale hollow core slabs (5.0 m span, 1.2 m width and 0.2 m thickness) were tested under flexure using four point loading up to failure, with one slab being tested as control specimen and the remaining six slabs strengthened with CFRP. Experimental results show that the flexural load carrying capacity of precast prestressed hollow core slabs increased in the range of 14 to 40% depending on the width/layers of CFRP sheets used. Interesting transition in the behavior of the hollow core panels from flexure to shear failure was noted as the number of layers of CFRP sheets was increased. A good correlation was observed between the experimental and the predicted values obtained using a strain compatibility approach.