Two-way Slabs having Openings Strengthened with Heavy-duty Metal Straps

Openings in slabs are commonly implemented to facilitate mechanical and electrical services; however, they considerably reduce stiffness, load-carrying capacity, and ductility, potentially changing failure modes. This study conducts an experimental analysis of twelve two-way normal reinforced concrete (RC) slabs, including one solid control slab, three unstrengthened slabs with openings at various locations (Middle, Corner, and Edge) in the specimens, and eight strengthened slabs utilizing Heavy-Duty Metal Straps (HDMS) which are thin steel strapping bands used externally as a strengthening system. The findings indicated that unstrengthened slabs with openings demonstrated considerable decreases in ultimate load capacity (up to 20% lower than the solid control) and flexural stiffness, with failure modes primarily transitioning to punching shear. The strengthening of corner openings restored the ultimate strength to levels similar to those of the solid control slab and increased stiffness by over 40%, in addition to improving ductility performance. The strengthening for middle openings resulted in partial recovery of stiffness and ultimate load, alongside significant enhancements in ductility. The performance of HDMS at edge openings was dependent on configuration; in the optimal arrangement, the technique nearly restored ultimate stiffness to the control level, while other configurations exhibited limited advantages.