Title: Seismic Resistance of Nonductile Slab-Column Connections in Existing Flat-Slab Buildings

Author(s): A. J. Durrani, Y. Du, and Y. H. Luo

Publication: Structural Journal

Volume: 92

Issue: 4

Appears on pages(s): 479-487

Keywords: columns (supports); connections; hysteresis; moments; slabs; reinforced concrete; stiffness; Structural Research

DOI: 10.14359/997

Date: 7/1/1995

Abstract:
Seismic resistance of slab-column connections in nonductile reinforced concrete flat-slab buildings was studied by testing two-bay connection subassemblies under earthquake-type loading. The test subassemblies were designed and detailed according to the gravity load design procedure practiced during the 1950s and 1960s. Each test subassembly consisted of two exterior connections and one interior connection and was a one-half-scale representation of the prototype building. Rapid stiffness degradation, significant reduction in drift capacity under increased gravity load, and limited moment-transfer capacity were among the main response characteristics of the nonductile slab-column connections. Flexural yielding of the slab was observed as the primary mechanism for resisting lateral loads. However, when heavy gravity load was applied to the slab, the interior connections punched before the slab reached flexural capacity. The lateral drift capacity of the connections was also significantly reduced with increased gravity load. The moment transfer at connections occurred primarily through negative bending of the slab. Under positive bending, the moment-transfer capacity was limited to flexural cracking strength of the slab. Since the nonductile slab-column connections did not have slab bottom bars continuous through the interior column, collapse of the floor slabs immediately followed the punching failure at interior connections.