Pioneer Square Areaways

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Pioneer Square Areaways

• Samir Chudgar, P.E., S.E.
• Chudgar Engineering Company
• Bellevue, WA, USA
• 425-881-8979
• 26th April, 2008

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What are Areaways?

• Space underneath the sidewalks
• Sort of extension of building basement under the
  sidewalk
• Seattle Department of Transportation, City of
  Seattle

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Sidewalk with areaway below it
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Map
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(No Transcript)
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Creation of Areaways

• Created over 118 years ago
• Streets raised after the Great Fire of 1889
• Street wall supports street and fill
• Building wall at basement
• Sidewalk structure spans street wall and building
  wall
• Space created below sidewalk
• 115 Areaways in Pioneer Square

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Features

• Street wall
• stone, brick, concrete, rubble
• Building wall or columns
• stone, brick, concrete
• Sidewalk
• steel or concrete beams
• brick arches, concrete slab
• End walls

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Structural Condition

• Deterioration in structural condition
• Street walls
• settlement, cracking, loss of mortar, tilt and
  rotation
• Sidewalk beams
• corrosion in steel beams
• spalling and cracking in concrete beams
• Brick arches
• Cracking, deterioration of bricks

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Corrosion in steel sidewalk beam
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Areaway 903 Damage

• Street wall of concrete (unreinforced)
• Damage
• settlement
• large cracks
• tilt
• Loss of support for sidewalk beams
• Risk to utilities through street wall and on
  sidewalk

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Areaway view
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Crack in street wall
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Rehabilitation

• New concrete retaining wall
• Supported on helical micropiles
• Resists all soil lateral loads, traffic
  surcharge, sidewalk weight and pedestrian live
  load

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Plan
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Section
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Street wall construction
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Helical Micropiles

• Two rows to resist compression and tension
• Limited headroom
• Low vibration
• Low noise
• Little set-up of equipment
• Community Sensitivity

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Street wall construction
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Historical Significance

• Brick arches
• Brick building wall
• Arched opening in building wall
• Constructing new street retaining wall on piles
  with pile cap keeps areaway space open and
  available for continued use
• Preserves areaway appearance

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Brick Arch
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Arched opening
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Monitoring Program

• Areaways monitored for
• Settlement settlement points
• Tilt tilt plates
• Cracks crack set points and crack gauges
• Selected 40 areaways in phase 1
• Baseline reading taken in year 2004