The Brooklyn-Queens Expressway (BQE), Interstate 278 between Atlantic Avenue and Washington Street in Kings County, is an approximately 1,500-m-long multiple-level highway reinforced concrete structure that was built in 1948. It is an important transportation link in the New York City metropolitan area and serves a daily traffic volume of 122,000 vehicles. The longest portion of the BQE consists of elevated one-, two-, and three-level cantilever structures. They are built into the hillside of Brooklyn Heights in successive levels, set back to provide light and air to three lanes of traffic in each direction. They have a unique configuration consisting of rigid frames supporting the roadways with long cantilevers, serving also as retaining walls supporting the hillside beneath adjacent brick buildings. The reinforced concrete portions of the BQE were modeled with finite elements that explicitly represented the concrete and reinforcement and used nonlinear material models. The displacement performance was determined in cyclic pushover analysis that predicted concrete cracking and reinforcing bar yielding. This performance was compared with recently developed displacement performance criteria to establish displacement capacities. The displacement demands were determined by time history analyses using nonlinear models. The methods and criteria that were used for evaluation of the BQE structures are described, and conclusions that may be applicable to future seismic evaluations using the displacement-based approach are provided. Other project challenges are also discussed, including the seismic effects of adjacent buildings and subway tunnels.
Samenvatting