Greater Buffalo International Airport Viaduct

Abstract

The Greater Buffalo International Airport improvement program being planned and constructed by the Niagara Frontier Transportation Authority includes a new elevated departure viaduct. The overall length of this structure will be 1439 feet consisting of a 14 span main structure of 502 feet, two approaches at 115 feet each, and two mechanically stabilized earth embankments at 340 feet and 367 feet. The main span deck is 67 feet wide which will accommodate two parking lanes, and two traffic lanes designed to AASHTO HS-20 loading criteria and a sidewalk. The deck consists of precast prestressed concrete slab units placed perpendicular to the traffic flow and cantilevered 13 feet on one end to support the sidewalk. Cast-in-place longitudinal beams support the precast slabs and cast-in-place transverse beams are located at each column to stiffen the structural frame. The longitudinal beams are supported by two rows of columns. Each pair of columns is on radial alignment approximately 52 feet apart. The preliminary analysis with conventional bearings resulted in high seismic forces on the columns and footing due to the very heavy superstructure. In an effort to reduce these forces, isolation bearings were evaluated. These bearings will be required to minimize displacements due to the close proximity of adjacent structures. In addition, the engineers were looking for a device that was a low height design which would function in cold weather. A sliding isolation system was selected with a positive restraint design which restores the structure to its original pre-quake position. This system was developed based on research conducted at the National Center for Earthquake Engineering Research located at the State University of New York at Buffalo. The use of sliding isolation on this structure resulted in significant force reductions while minimizing seismic displacement. The fact that all bearings are engaged in seismic resistance and energy dissipation resulted in mitigating seismic forces to a non-governing level.