Title: Shear Strength of Post-Tensioned Slab-Column Connections: Reevaluation of ACI 318-19 Code

Author(s): Giwan Noh and Thomas H.-K. Kang

Publication: Structural Journal

Volume: 121

Issue: 4

Appears on pages(s): 197-212

Keywords: flat plate; post-tensioned (PT); prestressed; punching; shear strength; slab-column connection

DOI: 10.14359/51740575

Date: 7/1/2024

Abstract:
Compared to conventional reinforced concrete (RC) flat-plate systems, post-tensioned (PT) flat-plate systems lack experimental studies on shear strength, and there are no studies that have been analyzed and collected with clear criteria (for example, calculation of effective depth, unbalanced moment, and measured shear strength) about experiments conducted so far. As a result, the current ACI 318-19, Section 22.6.5, for prestressed members has many restrictions based on the lack of experimental data on the nominal shear-strength equation. In this study, to reevaluate the nominal shear strength of the PT flat-plate system more reasonably and provide a reference for future studies, a total of 120 experimental data on the shear strength of the PT flat-plate system without shear reinforcement that have been conducted so far were recalculated and recompiled with clear criteria (the experimental data consists of 74 interior connections, 41 edge connections, and five corner connections). In addition, the factors affecting the shear strength and the validity of restrictions in the nominal shear-strength equation of ACI 318-19 were analyzed. The factors affecting the shear strength include: 1) method of loading; 2) presence of nonprestressed reinforcement; and 3) reinforcement ratio along the lateral load direction. The restrictions in the nominal shear-strength equation of ACI 318-19 include: 1) fc′ ≤ 4900 psi (34 MPa); 2) fpc ≥ 125 psi (0.9 MPa) (in each direction); 3) fpc ≤ 500 psi (3.5 MPa) (average in the two directions); and 4) it is applicable only for interior connections.