Title: Performance of Open Double Stirrups as Punching Shear Reinforcement

Author(s): Aaron Nzambi, Dênio Oliveira and Pedro Silva

Publication: Structural Journal

Volume:

Issue:

Appears on pages(s):

Keywords: anchoring; flat plate; open double stirrups; punching; shear reinforcement

DOI: 10.14359/51740870

Date: 6/4/2024

Abstract:
This study experimentally evaluated the mechanical performance of the new type of punching-shear reinforcement in five bidirectional reinforced concrete slabs subjected to symmetrical loading. The proposed shear reinforcement model consists of double-layered open stirrups anchored to the flexural reinforcement, installed after the longitudinal bars have been positioned, simplifying the construction process. The main variables were the transverse reinforcement ratio and the inclination of shear reinforcements. It was found that the higher the reinforcement ratio and the inclination angle, the higher the shear strength, as expected. The open double stirrups shear reinforcement provided more displacements; and increased the punching shear capacity by up to 36% and 40%, respectively, for vertical and inclined stirrups. Although closed stirrups are still widely used in construction, the proposed solution with open double stirrups demonstrated clear gains in punching shear resistance, indicating its potential for practical use as reinforcement in slab-column connections. In addition, a comparison with theoretical punching shear strength predictions from ACI 318, Eurocode 2, and NBR 6118 codes revealed conservative estimates with ACI 318, while NBR 6118 showed better accuracy.