stangmore east & west bridges by robert devenney
TRANSCRIPT
“Remediation of Half Joint Structures:
Stangmore East & West Bridges”
COLAS Papers Competition 2011
By Robert Devenney
Overview
•General Arrangement of a Half Joint Structure
•Amey’s Brief
•Scope of Special Inspection Works
•Refurbishment works
•Conclusions
•Questions
Robert Devenney
What is a Half Joint Bridge?
Durability Concerns
Prestressed Beam Prestressed Beam
Crosshead Beam
Bearing Bearing
A lot of water is trapped behind the
bearings leaving a high concentration of
chlorides above the crosshead beam rib
Chlorides make their way through weak areas
such as areas with cracks, poor compaction and
low cover
Some water makes its
way along the
crosshead beam nib and
down the half-joint to the
crosshead beam soffit
Water containing chlorides leaks from the road
through failed bridge deck joints and down through
the half-joint
Durability Concerns
What happens if durability is ignored?
How is Amey Involved?
•Joint venture contract
•Worth £250 million
•Design and Build
•Maintenance/Operation period
DBFO Package 2 Chart
Overseeing Organisation
Public Sector
Contract Area
A1
A4 M1
Standards and Policies relating to
Half Joint Structures
•Historic Design
•Moratorium (DfT)
•BA and BD 57
•IAN 53/04
•DEM 71/04
Special InspectionScope of Special Inspection:
1.Visual Inspection
2.Dust Sampling for chloride analysis
3.Half-cell survey
4.Resistivity readings
Visual Inspection
The visual inspection observed:
•Water Leakage with leachate
•Reinforcement corrosion
•Cracking with rust staining
•Spalling and delamination
Hatched area shows defective concrete
observed during the Visual Inspection
Dust Sampling
•Two dust samples at three locations on
each crosshead
•High chloride contents (BA35/90)
Half-cell / Resistivity
•High negative potentials
•Low Resistivity readings
Refurbishment Work
•Replace deck joints
•Concrete Repair
•Cathodic Protection
Deck Joints
Existing APJ replaced with Buried Joints
Concrete Repair
Hydro demolitionGuniting
Cathodic Protection
Discrete Anodes
Conclusion
•Safety Critical Factors
•Primary Source Permitting chloride
ingress
•Primary economical factors
References•Amey Consulting, “Further Special Inspection of
Stangmore East and West bridges” 2011
•http://www.laganconstruction.com/ - Accessed 01/02/2011
•“Commission of Inquiry into the collapse of a portion of the
de la Concorde Overpass” 2007
•Stangmore East Bridge Maintenance Manual
•Stangmore West Bridge Maintenance Manual
•BA and BD 57 (www.standardsforhighways.com.uk) and
IAN 53/04
•BRE Information Paper IP 21/86
•BA 35/90 (www.standardsforhighways.co.uk )
•ASTM C876-80
•BS1881:Part 201:1986
Questions
Fe Fe2+ + 2e -
Fe2+ + 2Cl- FeCl2
2Fe(OH)2 + 1/2O2Fe2O3 + 2H2O
1/2O2 + H2O + 2e - 2OH-
FeCl2 + 2OH- Fe(OH)2 + 2Cl-
2OH-
Fe3O4
γFe2O3
Fe3O4
γFe2O3
Anode
2e -
Cathode
Corrosion Cell in Concrete