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/306864
Cast-in-place and precast concrete combine to solve challenges at remote and beautiful construction site Located on Hawaii Belt Road on the island of Hawaii, Kealakaha Stream Bridge traverses a 165-ft-deep and 610-ft-wide ravine. This structure is situated approximately 33 miles northwest of Hilo and provides for traffic traveling from Hilo to the northern part of the island. K e a l a k a h a S t r e a m B r i d g e i s a 720-ft-long, concrete bridge with a radius of curvature of 1800 ft, a 6.2% travel way superelevation, and a 3.46% vertical grade. The bridge has three spans—180 ft, 360 ft, and 180 ft. It is approximately 48 ft wide and provides two 12-ft-wide travel lanes and two 10-ft-wide shoulders. Due to its close proximity to an active volcano, this bridge is subjected to high seismic activity. It was required to be designed for an acceleration of 0.4g. Contract Plans The original contract plans called for a three-span, single-cell box girder without a concrete overlay and with depths ranging from 10 ft to 20 ft. The 180-ft-long end spans were designed to be constructed on falsework. Due to the length required between piers and steep terrain below, segmental cantilever construction was selected as the best option for the 360-ft-long center span. In order to increase the period of the bridge and to decrease foundation loads, the 22 ft 11½ in. by 6 ft 8 in. rectangular piers were designed to be 42 ft tall. In addition, precast concrete casings were required around the bottom of the piers to isolate them from the backfill. A significant number of soil nails were required to stabilize the steep cuts needed to locate footings. These footings were supported by 5-ft 0-in.-diameter drilled shafts. value Engineering Change Proposal The contract was awarded in 2005. The contractor felt that a curved segmental box structure with a travel way superelevation plus shoulder slope with no topping was very difficult to construct. The slope, terrain, and environmental controls that the project would require, the deep foundations, and the soil nail walls, made access all but impossible. The contractor then contacted KSF Inc. to design a different bridge that would resolve the construction issues. I n 1 9 9 6 , t h e Wa s h i n g t o n S t a t e Department of Transportation (WSDOT) d e v e l o p e d t h e i r W 9 5 P T G " s u p e r girder" which was capable of spanning profile KEALAKAHA STREAM BRIDGE / NORTH HILO, HAWAII Br IDgE DESI gN E NgINEEr: KSF Inc., Honolulu, Hawaii P rIME CoNTrACTor: Hawaiian Dredging Construction Company Inc., Honolulu, Hawaii P rECASTEr: Central Pre-Mix Prestress Company, Spokane, Wash., a PCI-certified producer P oST-TENSIoNINg CoNTrACTor: AVAR Construction Systems Inc., Fremont, Calif. gIrDEr LIFTINg jACKS: Enerpac, Milwaukee, Wis. CoNCrETE SuPPLIEr: Yamada and Sons Inc., Hilo, Hawaii rEINForCEMENT SuPPLIEr: Associated Steel Workers Ltd., Kapolei, Hawaii by David Fujiwara, Harold Hamada, and Eric Y. Matsumoto, KSF Inc., Gary Iwamoto, Hawaiian Dredging Construction Company Inc., and Ian N. Robertson, University of Hawaii Kealakaha Stream Bridge Replacement The completed bridge with existing structure in the background was opened to traffic on March 20, 2010. Photo: Glenn Koki, Hawaiian Dredging Construction Company Inc. 22 | ASPIRE , Summer 2010 ASP10-1625.indb 22 6/21/10 12:20 PM