The Quebec Bridge Collapse August 29, 1907

Kiran Acharya

St109664

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Presented to- Dr Thanakorn

Contents

0 Location.0 Purpose of the Bridge0 History0 Hierarchical Management Structure0 Design0 Cause of collapse0 The aftermath0 The second Bridge0 Summary0 Conclusions

Location

Quebec Province

St. Lawrence River

Quebec Bridge

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Purpose for the bridge

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The river was approximately 1 km wide at its narrowest section, 58 m deep at the middle, water with velocity 13-14 km/hr. and tides as high as 5m.

The St. Lawrence River was the main channel of trade for Quebec during summer while during winter there were no trade due to frozen water.

The St. Lawrence River became a barrier to east-west transportation.

Fig. St Lawrence River in winter

St. Lawrence River

History0 In 1882 Quebec Bridge Company was granted the contract for the

bridge.0 Due to short finance, nothing was done until 1887 when the Quebec

Bridge was incorporated with the Railway Company.0 Now the new management demanded to get the project rolling a.s.a.p.

and Theodore Cooper, the most reputed engineer of that time became the main consulting engineer of the project. He was from the US

0 Cantilever type bridge was chosen to be superior to arch and suspension bridge as suggested by Gustav Eiffel and other noted engineers.

0 Proposals were called for in Sep 1898.0 Substructure- Davis Firm0 Superstructure- Phoneix Bridge Company(PBC), which had never

constructed any bridge longer than 90 m0 Initial design was produced by Peter Szlapka, which was reviewed and

approved by Cooper

Hierarchical Management Structure

Quebec Bridge & Railway

Company(Owner)

Theodore Cooper(Consulting Eng.)

Norman McLure(Onsite personal

assistant of Cooper)

Phoenix Bridge Company

(Contractor)

Edward Hoare(Onsite chief design eng.)

General workers & others

Design

0 Cantilever superstructure with two main supports placed 487.7 m apart and total length of 899.1m, however in May 1900 the span was increased to 548.6 m

0 Weighed a total of 28,122 tons.0 Cooper said that this would be the best and cheapest

plan and proposal.

487.7 m

144 m205.7 m 171.5 m

899.1 m

45.7 m

548.6 m

With this design the construction was started on 2nd Oct 1900.

Erection of the superstructure portion of the bridge begin on 22nd July, 1905

And the bridge collapsed on 29th Aug, 1907

at 5:30 PM19000 tons of steel fell into the river within 15

seconds75 workers were killed, only 11 could survive.

Only the standing structure was the supporting pier.

0 The bridge collapsed due to the buckling of the compression member

Compression members

Tension members

Fig. Bridge just before collapse

Causes of Collapse

0 Design Aspects

0 Technical Aspects

0 Ethical Aspects

0 Procedural and Professional Aspects

0 Financial Aspect

Design Aspect

Fig. The distribution of forces is clear in this demonstration using

chairs, poles, counterweights, and humans

Anchor Post AB in tensionUpper Chord BC, CD in tensionCentral Tower CE in compressionLower Chord BE, ED in compression

A Balanced Cantilever Bridge

Central Span

Cantilever armsAnchor arms

Fig. Schematic diagram of the bridge

Design Aspects

Initially the span of the bridge was designed for 487.7 m but later Cooper increased the span to 548.6m without recalculating the stresses.

He increased the original allowable stress for the bridge.

He allowed 145 Mpa for normal loading and 165 Mpa under extreme loading condition

His allowable stresses were higher than those in use today by 3.3-8.7%

These allowances were questioned, however, they were accepted solely on Cooper’s reputation

487.7 m548.6 m

Design Aspects

At that time the knowledge about the compression members were less developed and there was no methods for testing the compressive members.

P

P

x

y

Technical Aspects

0 The top and bottom chords for the anchor and cantilever arms were designed as straight members,

but as shown in fig they were slightly curved.

Fig. First Quebec BridgeFig. Second Quebec Bridge

0 This reduced the buckling capacity of the compression members

Technical Aspects0 The stressed were not

recalculated once Cooper increased the span from 487.7 m to 548.6 m.

0 The new stresses were 7% higher

0 The new weight was 10% higher

0 At the time this error was discovered a large portion of the fabrication has been completed and a considerable amount of bridge erection was finished.

Ethical Aspects

0 The workers had reported the bending of members as early as in June but the engineers did not stop the work.

0 Cooper’s decision were not questioned even when they seemed unusual because of his engineering expertise.

7L

8L

Date of Observation

Member

Amount of Deflection

mminches

June 15

  1.5 – 6.5 1/16 to ¼

June A3R & A4R1.5 – 6.5  1/16 to ¼

June A7R & A8R1.5 – 6.5  1/16 to ¼

June A8R & A9R1.5 – 6.5  1/16 to ¼

June A8L & A9L 19 ¾

August 6 7L & 8L 19 ¾

August 8L & 9L 8 5/16

August 20 8R Bent Bent

August 9R & 10R ------- -------

August 23 5R & 6R 13 ½

August 27 A9L 57 2 ¼ 

Procedural and Professional Aspects

0 Because of his ill health, Cooper controlled the project from New york and never visited the site once the construction of superstructure started.

0 There was no one on the job site qualified to oversee this type of work, or in position to make a decision

Funding

0 Since from the beginning the QBC had suffered a serious financial problem.

0 The PBC offered to prepare the plans for the bridge free of charge and in return the QBC would be obliged to give the contract for construction to PBC. So there was doubt about the fair competition in the tendering.

The QBC did not have enough fund to test for the critical members.

The Compression Member

0 When the compression member later tested, the lattice system failed explosively because its rivets sheared leading to the immediate buckling of the chord

0 The results confirmed that the chords were inadequately designed.

lattice

Fig. Test of modal chord

0 Of the 86 men who were still on the bridge at the time of the collapse only 11 survived

0 The Royal Commission attributed the failure to defective design and errors in the judgment of Theodore Cooper

0 Cooper’s career ended, and as a result he retired from public life and died in his home on August 24, 1919, at the age of eighty.

The Aftermath

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Was Cooper unaware about

the deflection of the member?

0 He was reported by his onsite inspector as early as in mid June.

0 He thought the bents were due to some reasons other than over stressing and did not stop the work.

0 However, later he accepted the problem and ordered to stop the work

0 But the bridge collapsed on the same day.NO

0 During 1905, the member A9L was dropped and bent while erecting.

it was repaired and placed in the structure.

Later it was found to be the triggering cause of collapse.

The Second Bridge

After the collapse the government took over the design and construction.

The c/s area for the critical compression member were increased to 230% of the original c/s area.Old-543,000mm2New-1,250,000

It also suffered collapse in 1916 when a casting in lifting apparatus broke and the center span fall into the water.

13 workers lost their lives.5000 tons of steel sank to

the bottom of the river to rest beside the wreckage of the first bridge, which still remains there today.

Centre span

0 The second bridge was finally completed in 1917 and it weighed two and half times as much as the first bridge

Fig. Second bridge

Summary

0 World’s greatest bridge was under construction with inadequate funds for both engineering works the construction process itself.

0 Such constraints delayed engineering analysis and led to the adoption of unconservative specifications.

0 Every conflict between safety and economy was resolved in favor of economy

0 The whole project was under control of a single person. There was no other independent authority for the cross check.

Conclusions(Lessons Learnt)

0 Modal testing should be done for every big and important structures.

0 Always place public safety at the forefront of your professional consciousness.

0 Maintain professional behavior and never let ego get the better of you0 Engineers and other in charge must be open-minded

to the ideas of the labors because many labors have years of working experience

0 Always there should be a cross check. Even experts can make mistakes.

0 All in all, have high standard of professional conduct, be true to yourself in terms of your capabilities and follow the Code of Ethics.

Any Questions?

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THANK YOU