Review of Laboratory Test Data for Combined Lateral and Gravity Shear Demands on Interior Slab-Column Connections

Abstract eng:
Flat slabs are a common floor system for commercial and residential buildings. Past earthquake damage has shown that slabcolumn (SC) frames are not a suitable main lateral-force-resisting system in regions of high seismic risk because of their relative flexibility and potential for brittle punching shear failures. However, SC frame systems are common lateral systems in regions of low-to-moderate seismic risk, as well as gravity systems in regions of high seismic risk where moment frames or shear walls are provided as the main lateral-force-resisting system. In such cases, SC connections must still maintain sufficient strength and ductility to resist gravity loads under the presence of inelastic deformations. In the last several decades, the two-way shear response of SC connections has been evaluated by a significant number of experiments. These experiments provide physical tests to examine and calibrate design methods. However, details for these tests can be difficult to obtain and differences in defining key response parameters can lead to inconsistencies in some of the summarized test results. In addition, design recommendations have in some cases been developed based upon a limited subset of the available laboratory test data that did not include more recent tests. To avoid these limitations, this paper documents a database of SC connection tests that uses consistent criteria for selecting key response parameters. The collected test results include interior reinforced concrete SC connections with and without shear reinforcement under combined lateral and gravity shear demands. The relationship between the limiting drift and gravity shear ratio is examined for the data. The laboratory test data are investigated with respect to the load simulation technique, failure mode, shear reinforcement, and slab span-to-thickness ratio. The laboratory test data relating limiting drift to gravity shear demand data is compared to the current ACI 318-14 relationship for evaluating the design lateral deformation demands for SC connections in Seismic Design Categories D, E, and F. Because of the importance of the gravity shear demand on the SC connection, influence of flexural reinforcement ratio, and slab thickness; this paper also summarizes provisions for determining the nominal two-way shear strength provided by the concrete in three building codes: ACI 318-14, JSCE 15, and Eurocode 2 (2004). The differences in the estimated two-way shear strength provided by ACI 318-14 versus the Japanese and European codes are reviewed for select specimens, and the impact of these differences on the computed gravity shear ratio is evaluated.

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