Behavior and Design of Large Structural Concrete Bridge Pier Overhangs. Revised

摘要

In designing large cantilever bent caps for use on recent projects under current211u001eAASHTO design specifications, designers were faced with considerable 211u001euncertainties. Questions arose when designers attempted to satisfy both 211u001eserviceability and strength requirements for a series of cap designs that mixed 211u001eboth non-prestressed and prestressed concrete solutions. The problems were 211u001ecomplicated because of uncertainty whether AASHTO corbel or deep beam provisions 211u001ewould apply. The resulting designs were highly congested, had poor 211u001econstructibility and high costs. This report outlines development of a new design 211u001eapproach involving use of strut-and-tie models (STM), as well as a mix of 211u001eprestressed and non-prestressed main flexural reinforcement. A series of sixteen 211u001ebent cap overhangs were designed, built at a reduced scale, and loaded to 211u001efailure. Deflections, crack patterns and widths, reinforced strains, and overall 211u001ebehavior were observed. Economic and constructibility issues were examined. The 211u001euse of T-headed anchorages was explored. A comprehensive design approach that 211u001econsiders both serviceability issues (deflections, cracking, crack widths, 211u001efatigue stress ranges, and side face crack control) and strength issues 211u001e(ductility, adequacy of STM design and analysis of flexural capacity) was 211u001edeveloped. Recommendations for design and detailing to improve behavior, reduce 211u001econgestions and improve constructibility are provided.