HomeMy Public PortalAbout8.2 Gold River Bridge ReportGOLD RIVER BRIDGEA SUMMARY of the FINDINGS OF THE CONDITIONS ASSESSMENT REPORT
The last train crossed the bridge on September 19, 1991.Since 2003, the bridge has supported only recreational uses.The bridge is ~100 years old; 25-50 years beyond its intended lifespan.BACKGROUND:
A draft condition assessment report was received by MOC on September 21, 2021. BACKGROUND:The new assessment could be compared to assessments conducted in 2001 and 2013. This allowed the engineers to determine the rate of deterioration and priority of repairs.
There are FOUR main structural components2. Stone and Masonry Piers3. Steel Girders1. Timber TrestlesThe strength of the bridge relies on these four systems working together4. Bearing PlatesBACKGROUND:
OBSERVATIONS: Timber Trestles•The lifespan of creosote timbers is typically 50 years•Many timbers are in very good condition. However, some have degraded rapidly in recent years due to: Animal and insect damageDecay VandalismRusting and missing hardwareCracked timbers
OBSERVATIONS : Stone & Masonry PiersPiers are intended to support downward forcesThey are not intended to support lengthwise or side-to-side forcesThe piers have degraded in recent years due to:Missing masonryCrackingShifting and cracked top caps – allows water to get inVegetation
OBSERVATIONS: Steel GirdersDegradation has progressed in recent years due to:Pitting and corrosion on flangesPack rust on lateral bracesSurface coating failure
OBSERVATIONS: Bearing PlatesBearing plates sit between the steel girders and the stone piersThis is an issue because the piers, whose condition is also compromised, were not designed to accommodate the lengthwise and side-to-side forces. The central bearings have failed and no longer slideCorrosion and no evidence of ‘sliding’ as would be expectedThis failure transfers the movement of the girders down into the piers creating a ‘vertical cantilever’. Think of how a flagpole wobbles at the top while the bottom stays fixed.The central bearings are designed to slide to accommodate the expansion/contraction of the steelThe east and west end bearings are fixed
CONCLUSIONS:The components of the bridge that were designed to move, no longer do.And the components that were not supposed to move, now do.
CONCLUSIONS:Yes, the bridge used to hold up trains. The question now is not: can the bridge support a train, ATV, bicycle, or hiker?BUTCan the bridge hold itself up?
CONCLUSIONS:It is highly unlikely that the bridge will fall tomorrow, next week, or next year.But the engineers cannot say with 100% certainty that it won’t.From the 2021 Assessment Report (page 24):“ “Click here to access the full report.
CONCLUSION:Based on this recommendation AND the awareness that we are approaching the cold season (steel contraction/movement + snow loads), MOC decided that the best course of action was to close the bridge to ensure public safety.
NEXT STEPS:MOC is responsible for the management of the bridge.The bridge is still owned by the Province of Nova Scotia.We will now begin to explore the best and most achievable options to maintain passage over the Gold River for all users in the short-term and long-term.Options include:•Repair•Reconstruction •New construction•Decommissioning
GOLD RIVER BRIDGEA SUMMARY of the FINDINGS OF THE CONDITIONS ASSESSMENT REPORT
The last train crossed the bridge on September 19, 1991.Since 2003, the bridge has supported only recreational uses.The bridge is ~100 years old; 25-50 years beyond its intended lifespan.BACKGROUND:
A draft condition assessment report was received by MOC on September 21, 2021. BACKGROUND:The new assessment could be compared to assessments conducted in 2001 and 2013. This allowed the engineers to determine the rate of deterioration and priority of repairs.
There are FOUR main structural components2. Stone and Masonry Piers3. Steel Girders1. Timber TrestlesThe strength of the bridge relies on these four systems working together4. Bearing PlatesBACKGROUND:
OBSERVATIONS: Timber Trestles•The lifespan of creosote timbers is typically 50 years•Many timbers are in very good condition. However, some have degraded rapidly in recent years due to: Animal and insect damageDecay VandalismRusting and missing hardwareCracked timbers
OBSERVATIONS : Stone & Masonry PiersPiers are intended to support downward forcesThey are not intended to support lengthwise or side-to-side forcesThe piers have degraded in recent years due to:Missing masonryCrackingShifting and cracked top caps – allows water to get inVegetation
OBSERVATIONS: Steel GirdersDegradation has progressed in recent years due to:Pitting and corrosion on flangesPack rust on lateral bracesSurface coating failure
OBSERVATIONS: Bearing PlatesBearing plates sit between the steel girders and the stone piersThis is an issue because the piers, whose condition is also compromised, were not designed to accommodate the lengthwise and side-to-side forces. The central bearings have failed and no longer slideCorrosion and no evidence of ‘sliding’ as would be expectedThis failure transfers the movement of the girders down into the piers creating a ‘vertical cantilever’. Think of how a flagpole wobbles at the top while the bottom stays fixed.The central bearings are designed to slide to accommodate the expansion/contraction of the steelThe east and west end bearings are fixed
CONCLUSIONS:The components of the bridge that were designed to move, no longer do.And the components that were not supposed to move, now do.
CONCLUSIONS:Yes, the bridge used to hold up trains. The question now is not: can the bridge support a train, ATV, bicycle, or hiker?BUTCan the bridge hold itself up?
CONCLUSIONS:It is highly unlikely that the bridge will fall tomorrow, next week, or next year.But the engineers cannot say with 100% certainty that it won’t.From the 2021 Assessment Report (page 24):“ “Click here to access the full report.
CONCLUSION:Based on this recommendation AND the awareness that we are approaching the cold season (steel contraction/movement + snow loads), MOC decided that the best course of action was to close the bridge to ensure public safety.
NEXT STEPS:MOC is responsible for the management of the bridge.The bridge is still owned by the Province of Nova Scotia.We will now begin to explore the best and most achievable options to maintain passage over the Gold River for all users in the short-term and long-term.Options include:•Repair•Reconstruction •New construction•Decommissioning