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Cincinnati and Northern Kentucky International Airport Taxiway N Bridge



The new aircraft-support bridge at the Cincinnati/North Kentucky International Airport required a novel approach due to severe loading and structural-depth requirements. Designers considered the options and decided on a single 87-foot-long, post-tensioned, cast-in-place span without any joists.

The bridge was designed and detailed as a simple-span structure to carry aircraft loading. To allow the contractor to erect falsework and pour slabs of a manageable size, the 217-foot-wide bridge was divided into three segments: two 72-ft-4-in.-wide outer segments and an inner segment that is 72-ft-2-in. wide. The segments are separated by a longitudinal expansion joint made of an expandable, watertight foam sealant and a strip-seal system at the roadway level.

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. The bents are supported by 13 48-in.-diameter concrete drilled shafts. The bridge provides the necessary 16-ft-11-in. of clearance over the roadway.

The approach slabs on each side consist of 24-inch.-thick reinforced cast-in-place concrete slabs supported on one side by a bracket protruding from the post-tensioned slabs and on the other side by a 6-ft-wide longitudinal sleeper pad. The approach slabs were designed as structural members on elastic foundations to carry the wheel load of the aircraft.

The concrete slab, which is 4-ft-6-in.; thick, was post-tensioned both longitudinally and transversely. The voids were made of 14 corrugated metal pipes, 30-inches in diameter, spaced at 4-ft-6-in. on-center per segment.

The longitudinal post-tensioning of each slab segment consists of 30 tendons. Each is composed of 27 0.6-in.-diameter strands. Two additional empty ducts were provided and capped for future use. The transverse post-tensioning features four 0.6-in.-diameter strands at 11-3/8 in. from the top of the slab. All post-tensioning strands are seven-wire strands conforming to ASTM 416 A416 270 ksi low-relaxation steel.

The result of this attention to detail and key concerns is a bridge that will support heavy aircraft loads for many decades of service to come. Using the new post-tensioning enhancement strategies will help reduce inspection and maintenance needs over its entire service life.

New post-tensioning specifications were used to increase the durability and performance level of the bridge.

Project Details

Location:

Erlanger, KY

Owner:

Kenton County Airport Board, Cincinnati, OH

Engineer:

PBS&J, Tampa, FL

Contractor:

The Harper Company, Hebron, KY

Total Project Cost:

$10.2 million (including approaches)

Total Project Size:

87 ft Overall Span,
217 ft wide plus approach spans

Resources

 
  • CRSI Case Study 90 KB pdf
    Case study for the Cincinnati and Northern Kentucky International Airport Taxiway N Bridge