Behavior of RC Flat Slab with Opening Strengthened with Steel Reinforcement

Abstract

This paper offering a wide-ranging study to investigate the punching shear behavior of reinforced concrete flat slab. The study involved of thirteen specimens tested under static load and divided into two groups; the study included one solid slab which considered the control slab. While the remaining slabs were parametric strengthened slabs with openings. The used variables were the opening size in addition to the strengthening of these openings by steel reinforcement. Six opening sizes (100x100, 150x150, 200x200, 250x250, 300x300, and 350x350) mm were constructed and tested under punching shear load. The results showed that the slabs behave linearly until it reaches about average value 23.5% of their ultimate strength for solid slab and by (17.2%) for the slabs with opening. The openings presence affected the load carrying capacity which decreased the cracking load by (45.8%) and ultimate load by (32.2%) when compared with the solid slab. Regarding the opening size, increase of the size led to decrease in the cracking and ultimate load of the flat slab which the opening with size of (350 x 350) mm caused maximum decrement which was by (60.75%) when compared with the solid slab. Reinforcing the opening with steel reinforcement could compensate the lost strength for small openings while the larger openings (greater than 150 x 150) compensated some strength due to the high condensation of shear stresses. The ductility of tested flat slabs was decreased with the existence of the opening and enhanced when the openings reinforced with steel reinforcement.