Title: Study on minimum shear reinforcement of flat slabs

Author(s): A. P. R. VAZ, R. B. GOMES, L. C. D. SHEHATA

Publication: IBRACON

Volume: 2

Issue: 1

Appears on pages(s): 01-24

Keywords: flat slabs, minimum shear reinforcement, reinforced concrete.

DOI:

Date: 3/30/2009

Abstract:
In a preliminary study that aims to define the minimum shear reinforcement of flat slabs that, leading to a punching shear failure surface that crosses that reinforcement, can avoid a sudden failure, nine slabs with 1800 mm x 1800 mm x 130 mm dimensions were tested. Their main variables were the number of shear reinforcement layers of the stud type, the cross-section area of that reinforcement in each circumferential layer and the diameter of the studs. In the attempt to define the minimum punching reinforcement of the slabs, a parameter ?, equal to the total force in the transverse reinforcement inside a truncated cone bounded by the shear crack divided by the punching strength of a similar slab without shear reinforcement, was used. The values of ? of the slabs varied between 0.27 and 1.03 and the punching failure surface crossed the shear reinforcement when ? was smaller than around 0.70. The value of ? equal to 0.6 was defined as close to the minimum for slabs with effective depth of 90 mm and flexure reinforcement ratio of 1.38%. In comparison with the slab with no shear reinforcement, slabs having ? of that order had a punching strength and rotation increase of about 10% and 30%, respectively