Technical briefing explaining what happen to the Forth Road Bridge and how we shall deploy a solution - 14th Dec 2015

1. Truss End
Link Failure
Forth Road Bridge
14 December 2015

2. Agenda
• Re-cap
• Progress
• Next steps

3. Location of failed section

5. RE-Cap Timeline of events
Tuesday 1 Dec:
• Failure of the inner link identified at 15:30
• Southbound carriageway closed
Wednesday 2 Dec:
• Engineers undertake structural inspection and assessment, which
progresses into the night.
Thursday 3 Dec:
• Bridge closes to HGVs at 14:30 following structural assessment
• Non-destructive testing results later that day identify likely crack in
remaining outer link
• Bridge closed
Decision was responsible, proportionate and had the support of
independent experts with past expertise

6. Re-Cap What Happened
• Physical Model made to illustrate

7. Re-Cap Potential Failure Mode

8. Re-Cap Potential Failure Mode

9. What’s Been Done So Far - Design
• Design was progressed day and night
• Temporary Access design & check - complete
• Hanging scaffold solution at 7 out of 8 areas
• Tower scaffold at 1 area (NE pier defence – eg. below failed
section)
• Large long reach access lorry, barged out to NE pier defence
• Repair design & check – complete
• Interaction with steel fabricator to inform design solution
• Steel manufacture; cutting & fabrication progressed in parallel
with design

10. What’s Been Done So Far - Site
• Safety of workforce paramount; Exceptional dedication in
face of challenging environment
Inspection & Testing
• All 8 similar areas visually inspected
• Localised paint removal & testing progressing
• 30+ rope access staff on site ; 40+ scaffolder’s on site ; circa
75+ other trades / staff on site ; 30+ welders mobilised
• CCTV camera observing crack 24/7
• Monitoring devices will be used to observe bridge behaviour
Temporary Access / Scaffolding (weather challenges)
• Temporary access scaffold erection underway at all 8 areas
• NE tower (failed section) 99% complete
• All 8 scaffolding areas programmed for completion mid week

11. Temporary Access
Hanging Scaffold System
(to 7 other locations)NE tower scaffold access from pier
defence (to failed section)

12. What’s Been Done So Far - Site
Construction
• Steel manufacture 100%
• Steel laser cutting 80%
• Steel Fabrication 70%
• Steel on-site 12.5%
• Steel Installation 0%

13. Controlled Test To Observe Structural Behaviour

14. NEXT STEPS - Fractured Link

15. Repair – Stage 1, Steel Plate welded in place
Animation Demonstration

16. Repair – Stage 2, Steel Plate welded to opposing face
Animation Demonstration

17. Repair – Stage 3, Steel Stiffeners welded in place
Animation Demonstration

18. Repair – Stage 4, Lifting jacks installed below member
Animation Demonstration

19. Repair – Stage 5, Jacks engaged to lift failed memeber
Animation Demonstration

20. Repair – Stage 6, Cover plate and welding completion
(Similar repair on adjacent side omitted for clarity, without jacks)

21. Truss End Connection Assembly
5 Primary Components
i. Tower
ii. Bracket (Extends inside tower)
iii. Post
iv. Link (failed above pin)
v. Pin