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/297030
The original Veterans Memorial Bridge (VMB), which was built in 1954, is an important link connecting the cities of Portland and South Portland, Maine, and spans the Fore River. While the existing bridge is still safe for use, the Maine Department of Transportation recognized that the old structure had met its life expectancy and made replacing the bridge a top priority. An alternative technical concept for a new bridge alignment was developed by the team of Reed & Reed and bridge designer T.Y. Lin International. The new bridge is being built upstream and at a slightly different angle from the older structure. This offers several significant advantages: • Overlap with the existing bridge was eliminated, greatly reducing impact to the 22,000 vehicles using the bridge each day. • Work over and adjacent to the active railroad was minimized. • The overall bridge length was reduced by nearly 800 ft. • T h e l e v e l o f s e r v i c e o f t h e intersections at the north end of the bridge will be improved. • The new location and alignment will result in a more popular and efficient entry point to the city. Superstructure The new segmental precast concrete bridge has a required 100-year service life and is a more visibly compelling structure for the cities it connects. It is designed to enhance the aesthetic experience and reduce the number of spans needed while providing Portland and South Portland with a signature bridge for this important transportation link. The VMB superstructure consists o f t w i n s e v e n - s p a n c o n t i n u o u s , variable-depth, single cell, trapezoidal box girders built using the balanced cantilever method. Typical span lengths are 250 ft each and end spans are 185 and 175 ft. The 1610-ft-long bridge is continuous from abutment to abutment; expansion joints are only required at each end. The superstructure is post-tensioned in both the longitudinal and transverse directions. The roadway is designed for two lanes of traffic in each direction with an additional 12-ft-wide, multi-use pathway. The superstructure is made up of two parallel precast concrete boxes built using the balanced cantilever method of construction and joined by a cast-in-place (CIP) concrete longitudinal closure strip. The 361 segments vary in depth from 8 ft 1 in. at midspan typical to 11 ft 1 in. at the piers. Segment length is 8 ft to 10 ft, with pier segments of 5 ft. The bridge is on a constant 1.33% longitudinal grade. Most of the alignment is straight with the north end having a 680-ft radius curve. The width of the north end also widens to accommodate a left turn lane. Here the width of each box top flange increases from 39 ft 9 in. to 45 ft 9 in. profile VETERANS MEMORIAL BRIDGE / PORTLAND-SOUTH PORTLAND, MAINE BRIDGE DESIGn EnGInEER: T.y. Lin International, Falmouth, Maine GEoTECHnICAl EnGInEER: GZA Geoenvironmental Inc., Portland, Maine PRIME ConTRACToR: Reed & Reed Inc., Woolwich, Maine PRECASTER: Unistress Corporation, Pittsfield, Mass., a PCI-certified producer PoST-TEnSIonInG ConTRACToR: DyWIDAG-Systems International USA Inc., Bolingbrook, Ill. CAST-In-PlACE ConCRETE SuPPlIER: Dragon Products Company, Portland, Maine by Christopher P. Taylor, T.Y. Lin International Veterans MeMorial Bridge The new bridge is being built on new alignment upstream at a slight angle to the existing bridge. Photo: T.Y. Lin International. t h e V i t a l l i n k f o r t w o c i t i e s Segment al bridge makes st atement in Maine 32 | ASPIRE , Summer 2012 P R O J E C T ASPIREBook_Sum12_R02.indb 32 6/29/12 12:39 PM