Modeling Parameters for Reinforced Concrete Slab-Column Connections

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Title: Modeling Parameters for Reinforced Concrete Slab-Column Connections

Author(s): Amy C. Hufnagel, YeongAe Heo, and Thomas H.-K. Kang

Publication: Special Publication

Volume: 297

Issue: 1-16

Appears on pages(s):

Keywords: reinforced concrete; slab-column connections; modeling; plastic rotation; seismic; evaluation.

Date: 3/6/2014

Abstract:
Over the past few decades, flat plate concrete building systems have been widely adopted in the United States and other countries because it enables not only to save construction time and cost but also to make better use of interior spaces. However, it has been observed that such buildings whose columns are cast into the concrete flat plate are highly vulnerable to collapse. Such integrated slab-column frames have suffered severe damage or completely collapsed during the past earthquake events. The main failure mode of these structures is punching shear. Although a general guideline for seismic design and a seismic rehabilitation design guideline for both existing and new reinforced concrete frame structures are specified in ACI 318 and ACI 369R, respectively, many uncertainties have still resided in the modeling parameters to accurately predict seismic behavior of the flat plate concrete frame structures. Therefore, a new chart of allowable plastic rotation values for correlating values of gravity shear ratio is presented in this study with the objective of updating the modeling parameters of ACI 369R. The major issues which lead to errors in evaluating flat plate concrete structural behavior under seismic loads are thoroughly investigated. Also, dominant parameters from previous and recent experiments on integrated slab-column connections subjected to seismic loading are utilized to assess the estimation of seismic performance of the flat plate system based on ACI 369R. Consequently, although it is confirmed that there is a trend in correlation between the allowable plastic rotation and gravity shear ratio while almost no correlation is observed with reinforcement ratio, more experimental data are necessary to enhance this correlation study. It is also noticed that the current ACI 369 recommendations for allowable plastic rotation values for slab-column connection under seismic and gravity loading are unconservative.