ACI 352.1R

Abstract

<em>Information and design recommendations have been summarized by Joint ACI-ASCE Committee 426 (1974, 1977). This guide is an update of ACI 352.1R-89 (Joint ACIASCE Committee 352 1989), based on research information presented in references such as Moehle (1996); Moehle et al. (1988); Kang and Wallace (2005); ACI 318-08, Chapter 21; and Cheng et al. (2010). Modifications to the previous report include expanding the coverage to include slabcolumn connections with shear reinforcement, slab-column connections with post-tensioning reinforcement, and lateral drift capacity of both RC and PT slab-column connections.</em> <br>These recommendations apply only to slab-column connections in monolithic concrete structures, with or without drop panels or column capitals, and using normalweight or lightweight concrete. For strength calculation purposes, the specified concrete compressive strength should not be taken greater than 6000 psi (42 MPa). The recommendations are limited to slab-column connections with slab thickness ranging between 5 and 12 in. (125 and 300 mm); a slab span-to-thickness ratio varying from 20 to 45, except for slab-column connections with transverse beams; and a ratio of long-to-short cross-sectional column dimensions less than 4. The recommendations for PT slab-column connections are applicable only for monolithic concrete connections with unbonded post-tensioning tendons applying an average compressive stress in the concrete not less than 125 psi (0.86 MPa). Construction that combines slab-column and beam-column framing in orthogonal directions at individual connections is included, but these recommendations are limited to issues related to the transfer of loads in the direction perpendicular to the beam axis. Slabcolumn framing systems are considered inappropriate as seismic-force-resisting systems assigned to high seismic design categories, but they are commonly used as frames not designated as part of the seismic-force-resisting system along with a stiffer seismic-force-resisting system, such as shear walls or beam-and-column moment-resisting frames. <br><em>These recommendations are limited to slab-column connections of cast-in-place RC and PT floor construction, including two-way ribbed floor slab construction (Meli and Rodriguez 1979) and slab-column connections with transverse beams. Recommendations are made elsewhere (ACI 352R-02) for connections in which framing is predominantly by action between beams and columns.</em> <br><em>The recommendations do not consider slab-wall connections, precast connections, or slabs-on-ground. Relevant information on these subjects may be found in ACI 360R-10, Schwaighofer and Collins (1977), Paulay and Taylor (1981), and Klemencic et al. (2006). Although structures having specified concrete compressive strength exceeding 6000 psi (42 MPa) are within the realm of this guide, the recommendations limit the assumed compressive strength for design to 6000 psi (42 MPa) because of the lack of test data on slabcolumn connections with higher-strength concrete.</em> <br><em>Slab-column systems are generally inadequate as the seismic-force-resisting system of multi-story buildings assigned to high seismic design categories because of problems associated with excessive lateral drift and inadequate shear and moment transfer capacity at the connections. For high seismic design categories, if designed according to these recommendations, slab-column systems may be used in multi-story construction in which earthquake-induced lateral forces are primarily carried by a stiffer seismicforce- resisting system. For low and moderate seismic design categories, slab-column systems may be adequate as the seismic-force-resisting system, provided the connection design recommendations in this guide are met.</em>