Title: Design and Detailing With Reinforcement For Seismically Resistent Concrete Bridge Structures
Author(s): D. Berner, T. Dahlgren, and K. Dahl
Publication: Symposium Paper
Appears on pages(s): 23-44
Keywords: anchorages; design; dynamic loading; reinforcing bars.
Headed reinforcement uses one or more anchorages, called heads, attached to the ends of steel reinforcing bars. Such heads serve to develop a bar in a relatively short distance, and can also better confine the interior concrete. For over a decade, headed reinforcement has had extensive field use in major structures subjected to cyclic fatigue and dynamic loading, as well as thorough laboratory testing on both bare steel bars as well as on concrete members with headed reinforcement. Such test have also demonstrated the superior performance of headed reinforcement under seismic loading conditions, even in high moment zones, and joint regions. This paper addresses both: (I) aspects of design and detailing with headed reinforcement for seismic resistance, and (ii) aspects of the concrete material performance as it is modified by headed reinforcement. Specific advanced design tools are discussed including empirical equations, strut-tie modeling procedures, a new membrane stress theory, and a new cyclic reinforcing bar bond-slip theory, together with design examples for bridge structures. Currently, ACI 349, CSA 474, and several overseas codes provide design rules for headed reinforcement. Where necessary these rules may be supplemented by experience, engineering judgment, empirical guidelines, and test results. New standards, regarding the use of headed reinforcement in concrete, are pending with both ASTM and ACI 318; which when incorporated should further facilitate the design process.