Title:
Reassessment of Two-Way Shear Equation in ACI CODE-440.11 Building Code
Author(s):
Zahid Hussain, Nima Khodadadi, and Antonio Nanni
Publication:
Structural Journal
Volume:
123
Issue:
4
Appears on pages(s):
29-40
Keywords:
building code; elevated slabs; glass fiber-reinforced polymer (GFRP) reinforcement; machine learning (ML); reinforced concrete; shear
DOI:
10.14359/51749551
Date:
7/1/2026
Abstract:
The two-way shear equation in ACI CODE-440.11 was originally developed nearly two decades ago using experimental data from early fiber-reinforced polymer (FRP) materials, most of which are no longer representative of modern glass fiber-reinforced polymer (GFRP) reinforcement. With current GFRP bars exhibiting significantly improved mechanical and surface properties, the validity of the existing equation requires reassessment to ensure practical and economical design. This study evaluates the ACI CODE-440.11 two-way shear provisions using a comprehensive database of 49 GFRP-reinforced concrete (GFRP-RC) interior slabs and 14 edge column connections. The current code equation was found to be highly conservative, yielding an average test-to-predicted ratio of 2.13. Updated equations are proposed for both interior and edge conditions, reducing the ratio to 1.02 and 1.04, respectively, while maintaining acceptable statistical variation. Additionally, symbolic regression (SR) is used to develop machine-learning-based expressions that show high predictive accuracy. The proposed models provide reliable, physically grounded, and less-conservative predictions of punching shear capacity, supporting broader implementation of GFRP reinforcement in structural concrete applications.
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