Main Street Bridge (Hillsboro, Oregon)

Main Street Bridge
Coordinates 45°31′17″N 122°57′49″W / 45.521416°N 122.963618°W / 45.521416; -122.963618Coordinates: 45°31′17″N 122°57′49″W / 45.521416°N 122.963618°W / 45.521416; -122.963618[1]
Carries MAX Blue Line
Crosses Main Street & 18th Avenue
Locale Hillsboro, Oregon
United States
Maintained by TriMet
Characteristics
Design concrete arch/tied-arch
Total length 425 feet (130 m)
Width 34 feet (10.3 m)
Height 75 feet (arch)
History
Opened 1997

The Hillsboro Main Street Bridge is a tied concrete arch bridge located in Hillsboro, Oregon. The bridge carries light rail traffic on the MAX Blue Line over Main Street and 18th Street. 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 with a vehicle clearance height of just 10 feet, 6 inches.[5] After abandonment of freight service on the line in the mid-1970s, the city required the successor railroad, the Burlington Northern Railroad, to remove the old crossing, in 1977.[5][6] In September 1997, the construction of the current 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. United States Geological Survey. 2010-03-11. Retrieved 2010-03-22.
  2. 1 2 3 Cortright, Robert. 2003. Bridging the World. Wilsonville, Or: Bridge Ink.
  3. 1 2 3 4 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. 1 2 Westside light rail the MAX Blue Line extension. TriMet. Retrieved on October 8, 2007.
  5. 1 2 Boatwright, JoAnn (September 15, 1998). "Bridge new ‘gateway to city’". The Hillsboro Argus, p. 8A.
  6. ↑ "East Main Overpass". The Hillsboro Argus. October 19, 1976. p. 18.
  7. ↑ Oliver, Gordon and Don Hamilton (August 29, 1997). "MAX moves west: New rail stations will go on-line". The Oregonian.
  8. 1 2 Oliver, Gordon and Don Hamilton (September 9, 1998). "Go west, young MAX". The Oregonian.
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