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/306162
EDU10-1782 The $172 million Pioneer Crossing p ro j e c t i n A m e r i c a n F o r k , U t a h , comprises 6 miles of new arterial h i g h w a y b e t w e e n t w o m a j o r development centers in Utah County and 1 mile of reconstruction of I-15, south of Salt Lake City. The new roadway serves a significantly growing community within the cities of American Fork, Lehi, and Saratoga Springs. The jewel of this new connector is its interchange with I-15—a diverging diamond interchange (DDI). T h e i n t e r c h a n g e w a s o r i g i n a l l y conceived by the Utah Department of Transportation (UDOT) as a single-point urban interchange (SPUI). The Request for Proposals, however, provided an Alternate Technical Concept (ATC) process that allowed individual design- build teams to develop, gain UDOT a p p ro v a l , a n d i n c l u d e i n n o v a t i v e concepts in their proposals for the project. The winning team submitted the DDI, including necessary traffic modeling analysis to support the concept. T h e D D I c o n c e p t h a d t w o m a i n advantages over a SPUI: reduced right- of-way requirements and increased safety for the traveling public. The DDI requires vehicles to briefly cross to the opposite side of the road at crossover intersections. Vehicles go a limited distance over the interstate before they cross back to the traditional side of the roadway. This layout reduces the number of conflict points by eliminating left turns crossing opposing traffic. The team was awarded the contract for the project in the fall of 2008, providing the cost benefit of the DDI and the time advantages associated with accelerated construction techniques. T h e D D I i n c l u d e s t w i n t w o - s p a n prestressed concrete girder structures t h a t re p l a c e d t h e e x i s t i n g f o u r- span structure over I-15. Traffic was maintained during construction of the DDI by phasing construction of the twin structures. Additionally, the individual superstructure spans were constructed adjacent to the existing interchange and moved into the final location using self- propelled modular transporters (SPMTs). Once in place, closure pours were placed to achieve continuity of the two-span structure. Layout and Bridge Design Once the preliminary alignments of the DDI were established, design of the structures began. The final in-place design for each bridge called for nine precast, prestressed concrete bulb-tee beams, each with a depth of 94½ in. and a maximum single unit length of 191 ft 9½ in. Each beam has a top flange width of 4 ft 6 in. and contains fifty-six 0.6-in.-diameter straight strands and eighteen 0.6-in.-diameter harped strands. Beam spacing was 7 ft 9 in. center to center and the geometric layout required a 53-degree skew at the abutments and center bent. The beam design required a concrete compressive strength of 10,000 psi at 28 days and 7,000 psi at prestress transfer. The beams supported an 8½-in.-thick, cast- in-place composite deck. During design, a specialist in heavy lifting and transport solutions was profile PIONEER CROSSING INTERCHANGE BRIDGES, I-15 TO REDWOOD ROAD / AMERICAN FORK, UTAH B RIDGE DESIGN ENGINEER: Parsons Corporation, Pasadena, Calif. PRIME CONTRACTOR: Kiewit/Clyde (A Joint Venture between Kiewit Western Co., American Fork, Utah, and W.W. Clyde, Springville, Utah) PRECASTER: Hanson Structural Precast, Salt Lake City, Utah, a PCI-certified producer CAST-IN-PLACE CONCRETE SUPPLIER: Geneva Rock, Orem, Utah HEAvy LIFT SUBCONTRACTOR: Mammoet, Salt Lake City, Utah by Steve Haines, Parsons Corporation pioneeR CRossinG A diverging diamond interchange on the move Completed diverging diamond interchange at Pioneer Crossing and I-15, American Fork, Utah. All photos: Kiewit/Clyde, a joint venture, and Parsons. 16 | ASPIRE , Winter 2011 P R O J E C T Book_Win11.indb 16 1/4/11 2:34 PM