ASPIRE is a quarterly magazine published by PCI in cooperation with the associations of the National Concrete Bridge Council. The editorial content focuses on the latest technology and key issues in the Concrete Bridge Industry.
Issue link: http://www.aspiremagazinebyengineers.com/i/306852
The new taxiway at the Cincinnati/ Northern Kentucky International Airport features a single post-tensioned, cast- in-place span to support the required loading and maximize clearance above the roadway. Photos: PBS&J. Designing the new aircraft-support bridge at the Cincinnati/Norther n Kentucky International Airport required a novel approach due to severe loading and the structural depth requirements. With a clearance of only 16 ft 11 in. over the roadway, a careful design had to be developed that could support the heavy weight of the aircraft and emergency vehicles using this bridge. After careful consideration of the options, a single 87-ft 2-in.-long, post- tensioned, cast-in-place bridge without any transverse joints was created. It was designed and detailed as a simple-span structure to carry the aircraft loading. To meet the variety of challenges, the 217-ft-wide bridge comprises three segments: two 72-ft 4-in.-wide outer segments and an inner segment that is 72 ft 2 in. wide. T h e s e g m e n t s a re s e p a r a t e d b y longitudinal expansion joints made of an expandable, watertight foam sealant and a strip-seal system at the roadway profile CINCINNATI/NORTHERN KENTUCKY INTERNATIONAL AIRPORT TAXIWAY 'N' BRIDGE / ERLANGER, kENTUCkY ENGINEER: PBS&J, Tampa, Fla. PRIME CONTRACTOR: The Harper Co., Hebron, ky. POST-TENSIONING CONTRACTOR: DSI America, Bolingbrook, Ill. GROUT SUPPLIER: Sika Corporation, Lyndhurst, N.J. STRAND SUPPLIER: Sumiden wire Products Corporation, Stockton, Calif. Severe depth limitations, heavy loads, and a short timetable created design challenges for this cast-in-place, post-tensioned concrete bridge level. Dividing the width into three segments allowed the contractor to erect the falsework and cast the slab for each segment individually. The post-tensioned voided deck is supported by plain elastomeric bearing pads that in turn are supported by 6-ft-deep by 4-ft 6-in.-wide end bents. Each bent is supported by thirteen 48-in.-diameter concrete drilled shafts. This approach was used due to the presence of limestone close to the soil surface throughout the entire project. The 30-ft-long approach slabs on each side of the bridge consist of 24-in.-thick cast-in-place reinforced concrete slabs supported on one end by a bracket protruding from the post-tensioned slabs and on the other end by a 6-ft-wide reinforced concrete transverse sleeper pad. The approach slabs were designed as structural members on elastic foundations to carry the wheel load of the aircraft. The retaining walls for the approach backfill are made of by Morad G. Ghali and Amir S. Ayoub, PBS&J Taxiway Takes flighT 36 | ASPIRE , Fall 2009 ASPIRE_fall09.indb 36 9/11/09 3:06:34 PM