Main Street Bridge (Hillsboro, Oregon)

Main Street Bridge
Carries	light rail
Crosses	Main Street & 18th Avenue
Locale	Hillsboro, Oregon United States
Maintained by	TriMet
Design	concrete arch/tied-arch
Total length	425 feet (130 m)
Width	34 feet (10.3 m)
Height	75 feet (arch)
Opened	1997
Coordinates	45°31′17″N 122°57′49″W / 45.5214160°N 122.9636180°W / 45.5214160; -122.9636180Coordinates: 45°31′17″N 122°57′49″W / 45.5214160°N 122.9636180°W / 45.5214160; -122.9636180[1]

Main Street Bridge is a tied concrete arch bridge located in Hillsboro, Oregon, United States. The bridge carries light rail traffic over Main Street and 18th Street on TriMet’s MAX Blue Line that runs from Gresham to Hillsboro. Completed in 1997, the 425-foot (130 m) long bridge was built with a 78-foot (24 m) tall arch in the center. It is located between the 12th Avenue Station and the Fair Complex Station.

Design

The bridge is a post-tension box girder structure with the center pier as an arch support straddling the road.^[2] Used in lieu of a center support, the arch is 110 feet (34 m) wide^[2] and 75 feet (23 m) tall.^[3] Six cables measuring four inches (102 mm) in diameter run from the arch to the main structure of the bridge at the center.^[3] The two ends of the reinforced concrete arch are connected to each other underground using a post-tension tie beam, making the structure a tied arch.^[2]

History

After more than a decade of studies and designing, construction on the Westside MAX light rail line began in 1993.^[4] In 1997, construction on the Main Street Bridge began. The bridge was designed by BRW to cross what is planned to be five lanes of traffic on Main Street.^[3] The city of Hillsboro required the bridge to be able to cross over the planned widening of the roadway without using a center support column, so as to prevent the kind of accidents that had plagued a previous crossing at the same location,^[3][4] a wooden trestle bridge of the Oregon Electric Railway, built in 1917.^[5] After abandonment of freight service on the line in the mid-1970s, the city required the successor railroad Burlington Northern to remove the old crossing, in 1977.^[5][6] In September 1997, the construction of the bridge structure was completed.^[7] The “golden spike” of the Westside light rail line was driven with the final pieces of track of the project installed on this bridge in October 1997.^[8] Passenger service on the $964 million project began on September 12, 1998.^[8]

References

Cables connecting the arch to the rail bed

1. ^ "Main Street Bridge". Geographic Names Information System, U.S. Geological Survey. 2010-03-11. http://geonames.usgs.gov/pls/gnispublic/f?p=gnispq:3:::NO::P3_FID:2582000. Retrieved 2010-03-22. 
2. ^ ^{a b c} Cortright, Robert. 2003. Bridging the World. Wilsonville, Or: Bridge Ink.
3. ^ ^{a b c d} Arch support for Tri-Met extension; engineers in Hillsboro, OR constructed a 75-foot (23 m) high concrete arch over a roadway without using a center support, so that the arch can support bridge cables for the light rail overpass; Transit Update. Railway Age, November 1997 No. 11, Vol. 198; Pg. 27; ISSN: 0033-8826
4. ^ ^{a b} Westside light rail the MAX Blue Line extension. TriMet. Retrieved on October 8, 2007.
5. ^ ^{a b} Boatwright, JoAnn (September 15, 1998). "Bridge new ‘gateway to city’". The Hillsboro Argus, p. 8A.
6. ^ "East Main Overpass". The Hillsboro Argus: pp. 18. October 19, 1976. 
7. ^ Oliver, Gordon and Don Hamilton (August 29, 1997). "MAX moves west: New rail stations will go on-line". The Oregonian.
8. ^ ^{a b} Oliver, Gordon and Don Hamilton (September 9, 1998). "Go west, young MAX". The Oregonian.

External links

• Media related to Main Street Bridge (Hillsboro, Oregon) at Wikimedia Commons
• Benjamin, Adam J. Portland MAX: East-West MAX (Blue). world.nycsubway.org