PROJECT: KYTC WHITLEY COUNTY I-75, EXIT 11
CLIENT: Kentucky Transportation Cabinet
This project was advertised through the Cabinet’s Design Build Initiative. The Design-Build Team of Kay & Kay Contracting and V&M was selected by the Cabinet based on price, innovation, and schedule.
This project was advertised with a scope of services that selected the type of interchange to be designed along with maintenance of traffic criteria to avoid any delays with the interstate system that this interchange would be serving. The type of interchange selected by the Cabinet to replace the existing rural diamond interchange was a Single Point Urban Interchange (SPUI). With this basic concept in mind, V&M proceeded to investigate some innovative ideas to adhere to the SPUI concept. After careful consideration, an hourglass-shaped bridge with exposed beams was selected for the preliminary engineering services to provide a summary of quantities to Kay & Kay for their bid.
Through later phases of the design process, a deck was added back to the exposed beams to accommodate a future landscaped area. V&M was also charged with the tasks of developing turning lane scenarios to provide, at least, a Level of Service C for this interchange. The resulting interchange would provide a 6-lane roadway across the bridge with dual left turn lanes in each direction to enter the interstate. Although not warranted for all legs of this interchange in order to meet the requirements for LOS, it was determined that all exit ramps off of the interstate would expand to two lanes prior to approaching the central intersection area of this interchange.
The final bridge configuration was a two-span 176’ long structure with Type IV PCI beams and continuous deck. The bridge was built in stages, with two in-line multi-column piers (one pier for each stage), and construction joints for the integral end bents and concrete deck. In order to facilitate adequate horizontal clearance along I-75, vertical MSE walls were detailed in front of the end bents. Special sequencing of the pile installation and wall geogrid units was necessary. Another special aspect of this bridge was the accommodation of signal pole structures at each side of the hourglass shape. The maximum out-to-out width was 166’-3”, and flared steel I-beams were utilized in the corners to support the acute angle geometry.
Another task associated with this project was to design the entrance and exit ramps to meet current AASHTO and KYTC guidelines without the need for additional ROW acquisition. Although these ramps had to be drastically changed from the existing ramps through the use of gravity-type retaining walls, the ability to stay within the limits of the existing right-of-way was achieved. The project design also addressed utilization of existing pavements as much as possible without disturbance to the traveling public.