Hoover Dam Bypass Bridge

//Hoover Dam Bypass Bridge

Hoover Dam Bypass Bridge

By |2020-08-13T17:35:57+00:00August 13th, 2020|Dam Repair|Comments Off on Hoover Dam Bypass Bridge

Hoover Dam Bypass Bridge

  • Concrete arch bridge
  • 1,900 feet long
  • Concrete arch – 1,000 feet
  • Pier caps are 7’ wide x 10’ deep x72’ long
Hoover Dam Bypass Bridge
Hoover Dam Bypass Bridge

Fire Damage

  • Fire Damage to east pier
  • Welding on top of pier cap
  • Sparks caused form work to smolder
  • Formwork smolder over weekend
  • Fire damage to underside of pier cap
Hoover Dam Bypass Bridge

Repair MethodGoal:

Achieve a durable repair

  • Remove damaged concrete using chipping hammers & hydrodemolition
  • Perform final preparation using hydrodemolition
  • Place new concrete using shotcrete method

Hydrodemolition Issues

  • 100% Tie off – Fall Protection
  • Accessibility – Handlance
  • Close working distance
  • PPE for handlance use.
Hoover Dam Bypass Bridge
Hoover Dam Bypass Bridge

Project PPE

  • Fall Protection – 100% tie off using double lanyard
  • Full Body armor
  • Waterproof steel toe boots with metatarsal protection
  • Rain suit
  • Waterproof gloves
  • Hearing protection
  • Hardhat
  • Safety Glasses
  • Face shield while blasting
Hoover Dam Bypass Bridge
Hoover Dam Bypass Bridge
Hoover Dam Bypass Bridge
Hoover Dam Bypass Bridge
Hoover Dam Bypass Bridge
Hoover Dam Bypass Bridge

Shotcrete Repair

Shotcrete was the recommend repair:

  • Accessibility
  • Quantity of material
  • Durability

FHWA Required Testing

  • Mix design submittal
  • Material Certifications
  • Compressive strength
  • Test panels for core grading
  • Shrinkage testing
  • Bond testing performed on field mockup

Shotcrete Specifications

  • Compressive Strength 6000 psi
  • Low to moderate shrinkage
  • Bond strength of

Material

Selected a pre-blended material:

  • Type 1 Portland Cement
  • Silica-fume
  • Aggregate –ACI 506.2 –Gradation #2
  • Design strength of 7,250 psi

Shrinkage

Shrinkage requirement: Low to Moderate

  • Cast 3 -3”x3”x11-1/4” prisms
  • Drying shrinkage measurements at 7, 14, 21 & 28 days
  • Avg. results –0.047%, 0.064%, 0.075% and 0.076%
  • ICRI TG 3733
    • –Low shrinkage = 0.025 –0.050%–
    • Moderate shrinkage = 0.050% -0.10%
  • Meets requirement

Test Panel Preparation

Three test panels were prepared to perform various test:

  • One unreinforced panel –wood form
  • One reinforced panel containing #11 bars @ 10” OC and #4 stirrup bars @ 6” OC –wood form
  • One reinforced concrete test panel made at the project site and shipped to the repair contractor’s site

Test Panel – 1

  • Unreinforced panel
  • Core grading –ACI 506.2 –Grade 2 or better –Excellent Results
  • Compressive strength –average 8,180 psi
Hoover Dam Bypass Bridge

Test Panel – 2

  • Reinforced panel
  • Core grading –ACI 506.2 –Grade 2 or better –Excellent Results
  • Core visually graded by FHWA officials.
Hoover Dam Bypass Bridge
Hoover Dam Bypass Bridge

Test Panel – 3

Reinforced concrete panel, water blasted with 20,000 psi to simulate hydrodemolition profile.

  • Bond test –ICRI TG 3739
  • Average direct tensile strength –259 psi @ 14 days
  • Shotcrete Approved for Repairs
Hoover Dam Bypass Bridge
Hoover Dam Bypass Bridge

Shotcrete Repairs

  • Approx. 60 cubic feet installed
  • Ridley C-9 dry mix gun•375 cfm
  • Shotcrete work accepted
  • Construction continues
  • Schedule completion of the arch bridge mid-2010
  • Open to traffic by the end of 2010
Hoover Dam Bypass Bridge

Arch under construction

Hoover Dam Bypass Bridge

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