8 Development of large-diameter reinforcing bars for the seismic resistance of reinforced concrete bridge columns

This paper presents an investigation on the bond-slip behavior and development of large-diameter bars embedded in well-confined concrete under seismic load conditions. Bond-slip tests and bar pull-push tests were conducted to characterize the bond strength, cyclic bond deterioration, and tension development of large-diameter bars up to No. 18 in size. A bond stress-versus-bar slip model was developed and implemented in a finite element analysis software. The model was validated with test data and used in a Monte Carlo simulation to evaluate the adequacy of the AASHTO requirements for tension bar development. Based on the results of this study, an improved development length formula was proposed. Furthermore, large-scale tests and finite element analyses were conducted to determine the minimum development length required for large-diameter bars connecting a bridge column to an enlarged pile shaft. Design recommendations were proposed based on the experimental and numerical results.