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

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

Publication: Structural Journal

Volume:

Issue:

Appears on pages(s):

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

DOI: 10.14359/51740575

Date: 2/14/2024

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 (e.g., 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 in the nominal shear strength equation. In this study, to re-evaluate 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 has been conducted so far were re-calculated and re-compiled with clear criteria (the experimental data consists of 74 interior connections, 41 edge connections, and 5 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, and the restrictions in the nominal shear strength equation of ACI 318-19 include: (1) f_c ≤ 4900 psi or 34 MPa; (2) f_pc ≥ 125 psi or 0.9 MPa (in each direction); (3) f_pc ≤ 500 psi or 3.5 MPa (average in the two directions); and (4) it is applicable only for interior connections.