Concrete Products covers the issues that attract producers of ready mixed and manufactured concrete focusing on equipment and material technology, market development and management topics.
Issue link: http://concrete.epubxp.com/i/75186
FEATURE COVER STORY PHOTOS: Washington State Department of Transportation (site); Concrete Products (sensor) SEATTLE SITE The use of precast/prestressed girders cast with high strength concrete is no accident at a major site like the Alaska Way Replacement southern mile: WSDOT recognizes the long-span, girder line and depth economy 10,000-psi product im- parts in bridge members. Agency officials likewise find lower fabrication, trans- portation and construction costs associ- ated with longer span bridges and optimized pier spacing. In addition to the 17 record-length WF100G girders (3,485 lineal feet), Con- crete Tech and Van Dyke have been coor- dinating delivery of 114 WF74G girders (16,614 lineal feet) and 34 WF girders, tapering from 74 in. deep at one end to 100 in. deep at the other (4,963 lineal feet), to the Seattle site. The southern mile of the $3 billion- plus Alaskan Way Viaduct Replacement is scheduled for 2013 completion under lead contractor Skanska USA. Girder erection has continued while Seattle Tunnel Partners, a joint venture of Dra- gados USA and Tutor Perini Corp., begins boring for a two-level structure running much of the western edge of downtown Seattle. The completed southern mile will remain a feeder route for the exist- ing viaduct leading up to the tunnel's 2015 completion. The Alaskan Way struc- ture north of the southern mile will then meet a fate similar to viaducts that once carried traffic along prime San Francisco and Boston waterfronts. Prepared by Don Marsh, Editor, and Siefkis- Petit Communications, Issaquah, Wash., from interviews with Concrete Technology and V. Van Dyke officials, plus Washington State Department of Transportation project profiles. 66 | JULY 2012 WWW.CONCRETEPRODUCTS.COM One of two V. Van Dyke tractor-trailers prepares to call it an evening after positioning the second to last of the 205-ft. beams. The 17 super girders span South Atlantic Street near sports venues Safeco Field (Seattle Mariners) and CenturyLink Field (Seattle Seahawks). The crossing (just above the pier formwork in aerial photo) is part of a half-mile of bridges within the first phase, or southern mile, of the Alaskan Way Viaduct Replacement. George Washington University researchers are conducting a two-year study of prestress loss on four of the 205-ft. girders. Concrete Tech placed vibrating wire strain gauges at midpoint and harp points: two rebar, one strand in the bottom flange, a fourth in the top flange rebar. The eight gauges will yield a stress profile over the depth of the girder. Researchers will observe prestress loss or gain attributable to deadload and deck shrinkage. Strain gauges embedded in deck concrete above each of the four wired super girders will contribute more readings. The project will augment the bridge engineering community's pursuit of data to clarify certain allowances in LRFD methods.