Recent advances in punching shear design of non-prestressed reinforced concrete slabs

Abstract

Reinforced concrete flat slabs are a popular choice for residential and commercial construction due to their practical advantages, such as simplified formwork and reduced floor heights. However, these systems are inherently susceptible to punching shear–a brittle failure mode that can trigger catastrophic progressive collapse, as evidenced by major structural failures like the Sampoong Department Store and Champlain Towers South, which resulted in loss of life as well as property. This paper reviews current punching shear design provisions across major international codes, including American Concrete Institute (ACI 318), Eurocode 2, and Indian Standards (IS: 456). While modern research emphasizes the critical roles of member size, flexural reinforcement ratio, and column geometry, standard codes fail to adequately address these factors. Specifically, ACI 318 and IS: 456 lack provisions for elongated columns and wall-slab connections where non-uniform stress concentrations significantly reduce capacity. To address these deficiencies, this paper reviews recent research on effective control perimeters and proposes updated expressions for the IS: 456 code. These proposed modifications integrate the size effect, reinforcement ratio, and elongated column geometry to provide more accurate and reliable predictions of punching shear strength for modern structural design.