A Simple Means for Reducing the Risk of Progressive Collapse

Published

December 1, 2013

Author(s)

Yihai Bao, Hai S. Lew, Fahim H. Sadek, Joseph Main

Abstract

A simple debonding technique is proposed to reduce or eliminate strain localization in reinforcing bars in the region of wide flexural cracks in RC beams, and as a result enhance the resistance of RC buildings to disproportionate collapse. In this study, three specimens with various lengths of debonding were tested. Debonding of the specimens was achieved by heat shrinking polyolefin tube over the reinforcing bar. The experimental results show that testing of a #8 reinforcing bar imbedded in concrete with 8-in (203 mm) debonding on both sides of a ¿ in (6.35 mm) wide gap allowed the bar to stretch about 38% more than the bar without debonding before fracture. This shows clearly that the debonding method can effectively reduce strain localization, thereby delaying the fracture of reinforcing bar. To analyze the debonding behavior, detailed finite element models of the three test specimens were developed. Good agreement between the computational and experimental results validated the computational method used in this study. Intermediate moment frame (IMF) beam-column assemblies were analyzed by applying the validated debonding model under a column removal scenario. The results show improvements of more than 30% in the vertical load carrying capacity with a debonding length of twice the depth of beam. This indicates that debonding enhances the development of catenary action in beams of RC frame structures.

Citation

Concrete International

Pub Type

Others

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Keywords

buildings, caternary action, computational model, concrete structures, debonding, disproportionate collapse, testing.

Citation

Bao, Y. , Lew, H. , Sadek, F. and Main, J. (2013), A Simple Means for Reducing the Risk of Progressive Collapse, Concrete International, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=914051 (Accessed October 29, 2025)