Strengthening of Flat Slab with Openings under Punching Shear Load

Abstract

This paper offerings a wide-ranging study to investigate the punching shear behavior of reinforced concrete flat slab with openings. The study involved of eighteen specimens tested under static load and divided into two series; the first group included flat slabs with openings while the second series were slabs with openings with varied compressive strength. The used variables were the opening location and number in addition to the compressive strength of slabs (40,50, 60, and 70 MPa). The results showed that the slabs behaves linearly until it reaches about average value 23.5% of their ultimate strength for solid slab and by (23%) for the slabs with opening. The openings presence affected the load carrying capacity which decreased the average cracking load by (31%) and ultimate load by (28%) when compared with the solid slab. Regarding the opening location, placing the opening near the central column led to decrease in the cracking and ultimate load of the flat slab with maximum decrement in the ultimate load was by (60.2%) when compared with the solid slab. increase of the compressive strength enhanced punching shear strength of the slabs with opening. The ductility and energy absorption of flat slabs were decreased with the existence of the opening and enhanced when the compressive strength increased.