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A Simple Means for Reducing the Risk of Progressive Collapse



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


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.
Concrete International


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


Bao, Y. , Lew, H. , Sadek, F. and Main, J. (2013), A Simple Means for Reducing the Risk of Progressive Collapse, Concrete International, [online], (Accessed July 14, 2024)


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Created November 30, 2013, Updated October 12, 2021