challenge unveiled !! - municipal engineers association … · 2015-12-02 · challenge unveiled !!...
TRANSCRIPT
Challenge Unveiled !! Structural Evaluation of the
Margaret Avenue Bridge - City of Kitchener
Shailesh Shah, M.Eng., P.Eng. Scott Davis, M.A.Sc., P.Eng.
MEA 56th Annual Workshop Friday November 20, 2015
Presentation Outline:
Introduction Structural Challenge Evaluation and Alternative solutions Conclusion/results
City of Kitchener Bridge Inventory
The Margaret Avenue Bridge has similar half joint and reinforcing steel design as the de la Concorde Bridge in Laval Québec, which collapsed in 2006, killing five (5) people and injuring many others.
Biannual 2012 inspection identified the Margaret Avenue Bridge as having an “Urgent” need for a more detailed structural evaluation
Drop–in span supported on Corbel ledge/
half joint
A Conventional Bridge? City of Kitchener hired AECOM for Structural Investigation Three span bridge over railway tracks
Maybe Not
de la Concorde Bridge Three span bridge Cantilever cast-in-place concrete (end spans and
over the piers) with expansion joint in the span Drop-in precast concrete girder span with half joint
Disaster
September 2006 - The de la Concorde Bridge
Reasons for Failure de la Concorde Bridge
Similar design and similar risks in half joint design
Margaret Avenue Bridge
Problems in the Design of This Type of Structure
Single load path design of cantilever Bridges normally have redundant support systems. This
type of bridge design does not have this redundancy and does not meet the Canadian Highway Bridge Design Code.
Insufficient shear reinforcement required by design codes of the time
Need for expansion joints introduces likelihood of freeze-thaw damage to the half joints
The half joints are not inspectable (hidden)
Failure mechanism is brittle and rapid
Report of the Commission of Inquiry into the Collapse of the de la Concorde Overpass
The main causes of the fracture and subsequent collapse were: Design Steel reinforcement was concentrated in
one layer, causing a weak plane. * Construction, the reinforcement was not installed in
accordance with the design, exacerbating the design weakness. *
A low quality concrete was used in the abutments causing poor freeze-thaw behaviour.
Extensive concrete removal and rebar exposure during repairs may have caused cracking of the cantilever.*
* Similar to Margaret Avenue Bridge
Bridge Evaluation
Legend
Steel Plate
Reinforcing Steel Bar
Vertical Load From Drop In
Span
Stiffener Plate
Longitudinal Ties
Lap Splice
Welds between Reinforcing Steel and Steel Plates
Diagonal Reinforcing Steel Tie
Reinforced Concrete Cantilever
• Reinforcing Steel Layout per design
Photo of reinforcing steel from 2003 rehabilitation No indication of inclined reinforcement
Bridge Evaluation
Bridge Evaluation
Reinforcing Steel Layout observed from construction photos
Assumed location of reinforcing steel bar
Failure mode (tested beam, de la Concorde Bridge) Conclusion of the Margaret Avenue bridge evaluation was that a possibility of similar failure existed.
Bridge Evaluation
Alternative Solutions 1.County of Huron – Crediton Bridge
Make girders continuous
Requires discrete girders
Alternative Solutions 2. OPG ICD Bridge Support drop-in girders from pier Requires clearance below the bridge
Alternative Solutions
3. Margaret Avenue Bridge
Why bridge not reinforced or repaired? No discrete girders, no clearance below the bridge
Recommendation: remove the bridge Not a ductile design
Reinforcing steel not installed correctly
Rehabilitation may have compromised the joint
Not inspectable
Failure is explosive and sudden
Based on AECOM’s Structural Evaluation Report the City closed the Bridge in June 2013 for safety concerns
Margaret Avenue Bridge
After evaluating short term and long term repair solutions, City decided to demolish and replace Margaret Avenue Bridge
Margaret Avenue Bridge
Newly built Bridge
Margaret Avenue Bridge
References
Commission of Inquiry into the Collapse of the de la Concorde Overpass, Government of Quebec, 2007
Evaluation of the Margaret Avenue Bridge Deck In-Span Joint and Pier Cantilevers, AECOM, 2013
For more information/Questions: Shailesh Shah, [email protected] Scott Davis, [email protected]