Efficient near surface mounting CFRP strengthening of pretensioned hollowcore slabs with opening - An experimental study

Carbon fiber reinforced polymers (CFRP) are commonly used in strengthening of civil infrastructure due to their superior mechanical properties. Near surface mounting (NSM) of CFRP laminates is an efficient strengthening scheme to restore the capacity of concrete elements. Hollowcore slabs are pretensioned precast concrete elements reinforced only with prestressing strands. Due to various service requirements, openings/cut-outs are provided in the slabs. Reinstating the capacity of hollowcore slabs lost due to the presence of openings is very important as openings can severely reduce the capacity of these slabs and alter the load distribution in the floor system. This paper investigates the efficiency of NSM technique using CFRP laminates in restoring the capacity of hollowcore slabs with openings. Ten full scale hollowcore slabs were tested at two shear span to depth (a/d) ratios and with two different locations of opening. Presence of opening reduced the ultimate capacity of slab by 44% and NSM CFRP strengthening fully restored the lost capacity based on a/d ratio. The adopted strengthening was more effective in shear dominated than in flexure dominated specimens. However, in both a/d ratios, good improvement in initial stiffness was observed due to NSM CFRP strengthening.