A SIMPLE METHOD OF ENHANCING THE ROBUSTNESS OF R/C FRAME STRUCTURES
Yihai Bao, Hai S. Lew, Fahim Sadek, Joseph A. 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 to enhance the resistance of RC buildings to disproportionate collapse (also referred to as progressive collapse). Debonding was achieved by heat-shrinking polyolefin tube over the reinforcing bar. The experimental results show that testing of a #8 reinforcing bar embedded in concrete with 8-in (203 mm) debonding on both sides of a ¿ in (6.35 mm) wide gap (simulating a flexural crack) allowed the bar to stretch before fracture about 38 percent more than the bar without debonding. This shows clearly that the debonding method can effectively reduce strain localization, thereby delaying the fracture of reinforcing bars. To analyze the debonding behavior, detailed finite-element models of the test specimens were developed. Good agreement between the computational and experimental results validated the computational method used in this study. RC frame structures were analyzed by applying the validated debonding model under column removal scenarios. The results indicate that the debonding method enhances the development of catenary action in beams of RC frame structures.
ACI Special Publication
disproportionate collapse, reinforced concrete frame, debonding, catenary action, nonlinear model