Comparison of flat slab strengthening techniques against punching-shear

Punching-shear capacity of slab-column connections in existing R/C structures may be inadequate to bear design loads, so strengthening works are required. The lack of punching resistance may be due to detailing, design or building errors; in other cases, such lack is due to a change of use, which requires an increase of resistance. Different techniques have been developed for strengthening R/C slabs against punching: enlargement of the support, gluing external fibre reinforced polymers or casting a bonded concrete overlay (BCO) on the slab’s top surface, insertion of post-installed steel bolts, application of fibre reinforced polymers cords as shear reinforcement. In the paper, the authors apply the Critical Shear Crack Theory (CSCT) to all of these techniques and evaluate their efficacy with reference to a case study.