Experimental and Analytical Study on Vertical Punching in Flat Plates with Stirrups
Journal
ACI Structural Journal
Journal Volume
123
Journal Issue
1
Start Page
89
End Page
103
ISSN
08893241
Date Issued
2026-01
Author(s)
Mogili, Srinivas
Abstract
Brittle punching failures in flat plates are precluded by ensuring adequate shear strength. Typically, this is achieved by adding shear reinforcement in the design. This paper presents an experimental and analytical study of flat plates to investigate load-resisting mechanisms associated with stirrup addition. The experimental program includes four isolated flat plates with parametric variations tested under monotonic punching loads. In terms of normalized shear strength, improvements of 22% and 29% were observed in flat plates with different layouts of stirrups, respectively, when compared with the reference specimen without stirrups. The role of longitudinal and shear reinforcements in punching resistance of flat plates was assessed through strain observations. Based on test findings, a physics-based analytical procedure for punching capacity estimation is proposed and verified using a database of 72 isolated flat-plate specimens. The proposed method provided reasonably accurate capacity estimates with an overall mean test-to-estimated capacity ratio of 1.06 and a low coefficient of variation (COV) of 13%. These estimates are also compared with capacity predictions using ACI 318-19 guidelines, which resulted in an overall mean capacity ratio of 1.58 with a COV of 22%. Based on experimental and analytical results, modifications to ACI 318-19 two-way shear provisions are suggested by incorporating the key parameters in shear strength estimations, which improved the prediction accuracy to a mean of 1.25 with a COV of 13%.
Subjects
ACI 318
analytical
design codes
flat plates
punching
reinforced concrete
shear strength
softened strut-and-tie (SST) model
stirrups
Publisher
American Concrete Institute
Type
journal article