1. Failures

2. The Ramsgate Walkway Collapse 1964
killed
4 people died

3. The Ramsgate Walkway Collapse

4. The Ronan Point Collapse 1968
4 people killed
Code of practice used :
CP114 Structural Design of Reinforced Concrete Buildings

5. Stability and robustness
Buildings of this type can be very robust

6. The Cleddau (Milford Haven) Bridge Collapse 1970
4 people died when the bridge collapsed under construction.
The diaphragm above the pier buckled causing the then cantilevering section of the deck to collapse.

7. The Cleddau (Milford Haven) Bridge Collapse 1970
At that time the use of finite element analysis was not well developed.
Doing a shell element model with non-linear geometry and non-linear material behaviour would have been a major achievement.
Nowadays it would be quite feasible and would certainly give warnings of the problem.

8. Failures 4 deaths Charles de Gaulle Airport 2004
Main reason for the collapse: lack of ductility to resist dynamic punching shear

9. Punching shear failure

10. Failures Millennium Footbridge, London 2000
Synchronous lateral excitation

11. Happened at night - no deaths
The Hartford Connecticut Civic Center
Roof Collapse 1978

12. The Hartford Connecticut Civic Center Collapse
Two major modelling errors were the main sources of this collapse. Second order effects (non-linear geometry) were important but not included in the model resulting in lower stiffness and higher internal forces than predicted.

13. The Hartford Connecticut Civic Center Collapse
Secondly the centroidal axes of the members were not coincident at the joints. This caused significant underestimates of moments in the members.

15. Sleipner Platform before collapse - 1991
No deaths but very high financial loss

17. Sleipner - Plan

18. Sleipner - Mesh at Tricell

19. Sleipner - Detail of Mesh at Tricell Junction

20. Plan of tricell

21. Calculation (checking model) for shear stress in tricell wall of Sleipner Platform
Operating Conditions: Span of Wall m
Effective depth mm, Pressure head m
Pressure at 67 m depth:
p =
gh =
1000 x 9.81 x 67 = 66x 104 N/m
= p x area =
66x 104 x 4.5 x 1.0 = 3000 x N
Load on 1.0 m strip at 67 m depth: W
Max shear: V
= W/2 =
3000 x 103 /2 = x 103 N
Shear stress in concrete:
vc = V/(bd) =
1500x103/(500x 1000) = 3 N/mm2
Maximum design shear stress (BS 8110 for unreinforced section):
vc (BS8110) = N/mm2

22. Sleipner Collapse
The collapse was due to the choice of an inadequate mesh of 3D elements for the walls of the tricells. The estimate of shear stress in the wall was about 1/3 of a realistic value.
The computational model was not valid

23. Hyatt Regency walkway collapse
dead

24. Hyatt Regency
Error in understanding the load path for the hangers - Modelling error
Fault in designer/contractor relationship
Lack of robustness

25. The Tay Bridge Disaster 1879
Completed in February 1878.
Longest bridge in the world at time - 2 miles.

26. View showing collapsed spans.
77 people killled
To date - worst structural accident in the British Isles.

28. Lifting of windward column.
This scenario is in accord with pictorial records and with evidence given at the inquiry. Figure 6 (where the windward side is to the right of the photograph) shows the two courses of masonry having been pulled up by the column bolts. For two of the piers (nos 29 and 31, the first and third navigation piers on the south side), the base level bracing remained in place. The Court of Inquiry Report (1880), paragraph 12, says - 'The distance at which the girders were found from the piers, is such as would result from a fracture and separation taking place in the piers somewhere above the base of the columns.’ The appendix of the report also adds - ‘An examination of the ruins of pier No. 32, being that over which the train was situated when the structure fell, indicates that the columns doubled up about their joints as the lower lengths of the westward 15-inch columns were pushed over to the west, or in the reverse direction to that in which the rest of the structure fell. A similar action in pushing back the westward columns is seen in piers Nos. 36, 39 and 40.’
Without the luxury of an action replay one cannot be certain about the sequence of events. We believe however that the analysis has provided satisfactory explanations for a number of observations and has added significantly to understanding of the collapse.
Pier No. 5 Looking North
Lifting of windward column.
(Dundee City Council, Central Library, Photographic Collection)

29. THE END