Effect of Longitudinal Hollows on Behavior and Capacity of High Strength Reinforced Concrete One Way Slabs

This work involves experimental study for the effect of longitudinal hollows on behavior of HSC one way slabs. Six slabs of 1000×450×70 mm were tested. The parameters of the study are number, diameter and volume of the hollows and flexural reinforcement ratio (ρ). The hollows were made by embedding PVC pipes. Presence of hollows reduces cracking and ultimate capacities of the slab. The reductions are larger with increasing number, diameter and volume of hollows. Maximum reduction in cracking capacity is 26.9 % when 32 % hollows are used with ρ = 0.45 %. Using 32 % hollows reduces the ultimate capacity by 12.9 % when ρ = 0.45 % and by 20.3 for ρ = 1.2 %. Using 32 % hollows with ρ = 1.2 % prevents the flexural failure to finally take place due to the bearing failure at supporting region. Increasing (ρ) has significant effect on ultimate capacity and this effect is smaller in hollowed slab than in solid slab. Presence of hollows increases deflection values and makes load – deflection response softer especially in advanced loading stages. Also, crack width values at service stage increases with increasing volume of the hollows. Longitudinal hollows have convergent effects in reduction of the ultimate capacity and ultimate loads that result to very small effect on slab adequacy for carrying the applied loads. This makes it is useful using the hollows in construction of one way slabs especially when HSC is used. Keywords: one way slab, hollow, high strength, cracking, ultimate capacit