Quebec Bridge
Coordinates: 46 ° 44 ′ 44 ″ N , 71 ° 17 ′ 17 ″ W.
| Quebec Bridge | ||
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| use | Railway and road bridge | |
| Crossing of | Saint Lawrence River | |
| place | Québec , Lévis | |
| construction | Gerber girder bridge | |
| overall length | 987 meters | |
| width | 29 meters | |
| Longest span | 549 meters | |
| height | 104 meters | |
| Clear height | 45.7 m | |
| building-costs | $ 25 million | |
| start of building | 1902 | |
| completion | 1918 | |
| opening | August 23, 1919 | |
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The Québec Bridge ( French Pont de Québec , English Quebec Bridge ) is a rail and road bridge over the Saint Lawrence River between the cities of Québec and Lévis in the province of Québec in Canada .
It was the largest bridge in the world in 1919 and collapsed twice while it was being built, earning it notoriety.
location
The Québec Bridge stands west of the city center at a point where the Saint Lawrence River is only 600 m wide between high and steep banks .
It is the last bridge over the St. Lawrence River before its estuary . The Pont Pierre-Laporte suspension bridge, opened in 1970, is around 200 meters upstream . Two overhead lines cross the current between the two bridges .
description
The Québec Bridge now has a railroad track , three vehicle lanes and a sidewalk and bike path. Originally, it had two tracks and two sidewalks, but no vehicle lanes, but a free field in the longitudinal axis. It has belonged to the Canadian National Railway since 1993 .
The Québec Bridge, opened in 1919, is similar in construction to the Forth Bridge in Scotland, opened in 1890 . Just as this is a steel boom - truss bridge with a suspended beam , thus a Gerber beam bridge . Unlike the Forth Bridge, with its three pillars and two main openings, the Québec Bridge has only two large pillars supporting the structure and one main opening, but with a span of 549 m (1800 ft ) it was the largest main opening of any bridge in the world, up to it was surpassed by the Ambassador Bridge in 1929 . It is still the largest tanner girder bridge in the world.
The Québec Bridge is a total of 987 m long and 26.9 m (88 ft) wide. It towers above the water level by 104 m and has a clear height above MHW of 45.7 m (150 ft). Its two mighty piers, standing on or just before the bank, support the 95 m (310 ft) high truss construction of the booms , which each 157 m (515 ft) to an anchor pillar on the bank and 177 m (580 ft) across the river cantilever. The gap above the river is closed by a 195 m (640 ft) long suspension girder, which as an independent truss bridge would already have a considerable span. Its curved upper chord is connected to the horizontal lower chord, which makes its peculiarity visually recognizable. The connection between the main bridge and the high banks is made by two comparatively inconspicuous lattice girder girder bridges with an overhead carriageway and spans of 48 + 34 m and 43 m.
Although the bridge has the same span as the original, collapsed structure, it differs from it in other dimensions.
history
background
Before the Québec Bridge was built, the Saint Lawrence River was crossed by ferry or via the winter ice road; however, during the ice drift all communication was broken. Because of the water depth of around 60 m, a bridge could not be built with numerous river piers, unlike the first bridge over the river, the Pont Victoria in Montreal , which opened in 1859 , but had to cross the river with a span that was previously unattainable. Since 1852 various proposals for the construction of a bridge have been made, but they were not pursued further due to insufficient financial means and because of the technical risk. A law of 1887 gave the newly founded Quebec Bridge Company the license to finance, plan and build a railroad bridge (possibly also with lanes for road traffic) within six years, although it was free to build the connecting railroad lines. The deadlines had to be extended several times, for example in 1891, 1897, 1900 and 1903, as the Quebec Bridge Co. could not raise the financing either. At least in the years between 1897 and 1891 the future location of the bridge was finally selected from three alternatives, however without carrying out any major subsoil investigations.
Preliminary draft and tender
Edward A. Hoare had been appointed chief engineer of the Quebec Bridge Co. , but his experience was limited to bridges with spans of no more than 100 m. He used a meeting held in Quebec in 1897 to invite some representatives of the Phoenix Bridge Company , Pennsylvania , USA, a respected and experienced bridge construction company, to a tour of the future construction site. Theodore Cooper, also a respected and experienced bridge engineer from New York City, who had worked with the Phoenix Bridge Co. on several occasions, also attended the meeting. At the end of 1897, the Phoenix Bridge Co. sent the first drafts of a cantilever bridge with pillar spacings of 488 m (1600 ft) to the Quebec Bridge Co., which in turn submitted them to the government's Railway Committee, which granted the necessary approval in May 1898. Subsequently, the Quebec Bridge Co. and the Railway Department of the government prepared the specifications for a tender, which, however, largely corresponded to the usual specifications of the Railway Department without going into the specifics of the planned, exceptionally large bridge.
Although it was well known that the Quebec Bridge Co. lacked the funds to build the bridge, in September 1898 they published a tender with the specifications. The bidders were asked to submit a package price offer with draft plans for a cantilever bridge according to the specifications or for another type of bridge. In March 1899, six offers were submitted, some for a suspension bridge, with only the offer from Phoenix Bridge Co. containing complete planning documents.
At the time, the Quebec Bridge Co. appointed Theodore Cooper as a consulting engineer to review the plans and the submitted offers. In June 1899, Theodore Cooper stated that the Phoenix Bridge Co. offer met specifications and was the best and cheapest of the offers submitted. He suggested test drilling in order to determine the exact position of the pillars. In future contracts it should therefore be provided that the spans could still change in this respect. Cooper stated in his report that the second best offer was significantly more expensive because it contained almost 20% more steel. The Quebec Bridge Co. has not yet been able to place an order due to a lack of funds.
After further investigations into the subsoil, Cooper proposed in May 1900 to enlarge the main opening from 1600 ft to 1800 ft. This would avoid the difficult, time-consuming and costly pillar foundations in the river. The Quebec Bridge Co. accepted the proposal and the Phoenix Bridge Co. prepared accordingly modified draft plans.
At the same time, the Quebec Bridge Co. commissioned Cooper as a consulting engineer to examine and approve the plans to be submitted to him by the Phoenix Bridge Co. in his New York office and to advise on problems associated with the construction. Both sides agreed that this does not include the work of a chief engineer who directs and supervises the planning and construction of the bridge on the construction site. Cooper was never on the construction site during the steel construction work, he only visited the production facility in Phoenix three times.
The bridge should have two railway tracks and two tracks for road traffic with tracks for a tram and two sidewalks. The 20.4 m (67 ft) wide Gerber girder bridge was to have a main opening with a span of 549 m (1800 ft), that of two cantilevers with each 171.5 m (562 ft 6 ″) and a suspension beam of 205.7 m (675 ft) length was formed. The side openings were to be formed by 152.4 m (500 ft) long anchor girders. Truss girder bridges were supposed to create the connection to the high banks.
It was planned to first assemble the southern half of the steel superstructure. The anchor beam was made on scaffolding. Then a large, 990 t heavy crane, which could lift up to 140 t, and a smaller crane was erected on top of it. Both cranes could move back and forth on the upper chords of the construction. The cantilever arm and the southern half of the suspension beam were to be erected using a cantilever. Then the large crane was to be dismantled and used on the northern side for the construction of the other half of the superstructure.
Planning, first construction work
In 1902 the foundation stone was laid and work on the substructure began.
In 1903 the government began the National Transcontinental Railway project , for which the bridge in Québec was an important link. The company, now trading as the Quebec Bridge and Railway Company , now received sufficient public funds so that it was able to conclude the final steel construction contract with the Phoenix Bridge Co. in June 1903, which finally came into effect in March 1904. Instead of the original all-inclusive price, a price per ton of steel installed had been agreed. The Phoenix Bridge Co. would do the planning and assembly of the steel parts that were manufactured and supplied by its sister company, the Phoenix Iron Co. When Mr. Schreiber said on the part of the Railway Department that the agency should employ its own engineer to review and approve the plans in accordance with the financing agreements, Cooper vehemently opposed this, as he was not accepting any subordinate position. This was universally accepted; This gave Cooper the position recognized by all involved as the highest technical authority in this project.
It was also around this time that Cooper made the changes to the specifications made necessary by extending the wingspan to 1,800 feet.
The planning office of the Phoenix Bridge Co., headed by Peter Szlapka, began with the implementation planning, initially for the anchor arm. The weights of the cantilever arm and the suspension bracket had to be taken into account, which could only be estimated at this early stage. It was therefore necessary in the further course to calculate the actual weights resulting from the planning, to compare them with the initial assumptions and to take any necessary corrective measures. In the case of bridges with an everyday span and construction, this can often be omitted, as the planning engineers can estimate the weights with sufficient accuracy.
The execution planning was initially based on a total weight of the southern half of the bridge of 31.4 million pounds . The creation of the execution and work plans went according to routine. During a discussion of the static calculations, Szlapka told Cooper that his best people had calculated the weights individually and carefully and that he was convinced that the assumptions and calculations were correct. Cooper accepted this, probably also because without a large staff he would not have been able to check the weights.
Steel construction work
In July 1904, Phoenix Iron Co. began manufacturing the first parts. The planning of the anchor arm was largely completed in early 1905. The actual steel construction on the construction site began in July 1905 with the anchor piers. Determining the actual weights at this point in time would not have had any serious consequences; the necessary changes could have been made without further ado. However, actual weights were only determined for individual, very heavy parts, the transport of which had to be specially prepared.
Cooper did not become aware of the actual higher weights until February 1906, when more than half of the anchor arm was erected. He estimated the resulting increase in stresses at seven to ten percent, then decided that the additional loads were within the permissible tolerances and allowed the construction work to proceed. The momentous decision may also have been influenced by the fact that an immediate halt to construction and a complete redesign of the bridge would have jeopardized the financing of the entire project and thus his own career.
The construction work went without any particular problems. At the beginning of August 1907, almost all the rivets were set on the anchor arm after the steel profiles had only been temporarily attached with bolts during assembly . The planned dismantling of the large crane in order to use it on the north side was largely completed in August 1907.
Since the calculations made in the preliminary design phase regarding the total weight were not further checked and adjusted during the implementation phase, the dead weight of the bridge - unnoticed by all involved - increasingly approached its load limit.
In June 1907 problems arose with riveting because different profiles of the lower chords did not fit together exactly. However, this was not classified as a cause for concern. On August 6, 1907, the team of engineers on site, led by Norman McLure, noticed unusual deformations in other parts of the lower chords.
Concerned by these observations, McLure immediately wrote to Cooper, who initially classified the problems as minor. Those responsible at the Phoenix Company, the executing company, claimed that the steel girders had already been deformed before assembly. Others said the deformation was the result of an accident during assembly. The causes of the deformations were discussed and corresponded for a few days. The Phoenix Bridge Co. was obviously unaware of the drama of the situation. None of the engineers on the construction site felt sufficiently competent or able to order a construction freeze. On the contrary, Edward A. Hoare, as the highest-ranking engineer, even welcomed the fact that the attention associated with a construction freeze had been avoided.
On August 27, 1907, McLure realized the extent of the problems. In order to keep the matter a secret from the staff on the construction site, however, he did not dare to telephone or telegraph Cooper, but traveled to New York and two days later informed Cooper personally about the situation in his office. When Cooper saw the real extent of the problem during this conversation, he immediately telegraphed instructions to the Phoenix Bridge Company not to add any further loads to the bridge until the situation was clarified. Due to a misunderstanding, he assumed that work on the construction site would be suspended and that a telegram sent to the Phoenix Bridge Co. would have the decisive effect. It did not occur to either Cooper or McLure to send a telegram of the same name directly to the construction site.
Collapse on August 29, 1907
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However, the telegraphic message was not forwarded to the construction site by Phoenix Bridge Co. in good time and work on the bridge continued. On the same evening of August 29, 1907, at 5:32 p.m., the lower pressure chords 9L and 9R of the anchor arm buckled, whereupon the entire southern part of the bridge collapsed under its own weight and collapsed within 15 seconds.
At the time of the collapse it was the end of the day's work and the workers were getting ready to leave the bridge. When they noticed the collapse, many tried to leave the bridge, but only a few succeeded. The steamship Glenmont was just about to pass the bridge when it collapsed and immediately took part in the unsuccessful search for survivors. That night you could still hear the moaning of the dying in the ruins of the bridge on the bank, but you could not help until the following morning. The noise of the collapse of the bridge could be heard as far as Quebec, residents left their homes thinking of an earthquake.
In this serious accident 75 of the 86 workers on the bridge died. Among the victims were 33 Mohawk Indians from the nearby Kahnawake Reserve near Montreal, who were buried under crosses made of steel beams. The other parts of the anchor arm and the pillar that fell onto the bank were later transported away by a scrap dealer; the parts of the cantilever arm and the suspension beam that fell into the deep water are still there today.
Investigative commission
As early as August 31, 1907, the government (Governor General in Council) set up a commission of inquiry with the right to summon and examine witnesses. It consisted of Henry Holgate, Montreal (Chairman), John GG Kerry, Campbellford, Ontario, and John Galbraith, Toronto.
The commission examined all aspects of the history and implementation of the project. She found that the weight of the steel structure had increased by 24% from the initially estimated 31.4 million pounds for the southern half to the actual 38.8 million pounds without being taken into account in the planning. She dealt in particular with the lower chords consisting of four web plates with diagonal and right-angled grating made of flat iron, which had never been used in a structure of this size. Strangely enough, no pressure tests were carried out with them, although the Phoenix Iron Works had the largest test facility of its time. The knowledge of the professional world about the buckling behavior of compression members was insufficient to plan a construction of this size.
In its report of February 1908 the commission came to the conclusion that
- the collapse was caused by the failure of the lower chords of the anchor arm due to poor plans drawn up by PL Szlapka, the planning engineer of the Phoenix Bridge Co., and reviewed and approved by Theodore Cooper, the consulting engineer of the Quebec Bridge and Railway Co. be;
- however, the shortcomings in the planning were not due to a lack of specialist knowledge or negligent behavior or a desire to save costs. Rather, the two engineers were working on one of the most difficult problems in their field at the time, which they were not up to;
- the specifications were not sufficient, especially since the loads on individual bars were greater than was to be expected based on previous experience;
- A serious mistake was the too low weighting and failure to correct this approach later. This error would have been sufficient to reject the entire bridge, even if the lower chords had withstood the loads, since the loads occurring would have been greater than permitted according to the specifications;
- none of the people involved in the draft fully understood the size of the task at hand and the inadequacy of the data on which their planning was based. Tests to check the assumptions made had not been carried out;
- the specialist knowledge of the time about the behavior of steel rods under pressure was not sufficient to plan structures such as the Québec Bridge economically. An undoubtedly safe bridge of this span could have been built, but on the basis of the existing knowledge, considerably more steel would have had to be used than would have been necessary with better knowledge.
The members of the commission of inquiry also wrote in their report: “We are convinced that none of the people involved in the execution expected an impending accident and we believe that in the case of Mr. Cooper, his assessment of the situation was justified. He assumed that the assembly work would not be continued, and without the additional loads the bridge might have held for days. "
From the report it can be seen, however, that the collapse, but the accident with many fatalities, could have been avoided if the Quebec Bridge Co. had ensured that the construction site was manned by a competent and experienced chief engineer at all times if John Deans, the chief engineer of the Phoenix Bridge Co., had recognized the danger in the hours before the collapse and had not reacted negatively.
The report on the design of Quebec Bridge by CC Schneider was attached to the investigation report , in which he recalculated the planning in detail and outlined reasons for the failure and solutions for a new planning. Othmar Ammann , who works in Schneider's office, was involved in the report without being named .
Theodore Cooper's career ended with the collapse of the Québec Bridge. He retired from public life as a result of the events and died on August 24, 1919.
The collapse and its causes were discussed in detail among German engineers even before the final report was published. There, too, the insufficient knowledge about the buckling strength of steel rods was emphasized, which became the subject of further discussion contributions after the publication of the investigation report.
New building
After the investigative commission had finished its work, the Railway Department put out a tender for a new building based on a plan it had drawn up itself, which took into account the results of previous investigations. The planning envisaged the same span, but a modified construction with straight instead of curved belts in the brackets and a slightly shorter suspension beam and was much more massive.
The construction was carried out under the direction of chief engineer Ralph Modjeski . The cantilever arms were again cantilevered over the river. The suspension beam was mounted nearby on the bank, so that it could be transported to the bridge and lifted into place with three barges .
Second collapse in 1916
On September 11, 1916, the 5,000 t suspension beam was to be brought into its final position between the two booms in multiple lifting processes, which was viewed as the most difficult part of the entire assembly. The suspension rack fell into the river, killing 13 people. The later investigation revealed the failure of a bearing part used in the lifting process that was not optimally designed as the cause. The debris of the suspension bracket is still lying in the 60 m deep St. Lawrence River.
completion
The suspension bracket was made again and transported to the bridge in September 1917. This time, the collection process was spread over four days and was successfully completed on September 24, 1917. On December 3, 1917, a track was provisionally put into use. Because of the First World War , the final completion took until August 1918. A year later, on August 22, 1919, the grand opening by the Prince of Wales , the future King Edward VIII took place.
The bridge was designated a Historic Civil Engineering Landmark by the American Society of Civil Engineers in 1987 and a National Monument of Canada on January 24, 1996 .
Web links
- Royal Commission: Quebec Bridge Inquiry, Report; also Report on Design of Quebec Bridge by CC Schneider . Ottawa 1908 (English, archive.org [PDF; 2 kB ]).
Individual evidence
- ↑ The Québec Bridge not only surpassed the Forth Bridge with a span of 521 m, but also the New York suspension bridges of that time, i.e. H. the Brooklyn Bridge with a span of 485 m, the Williamsburg Bridge with 488 m and the Manhattan Bridge with 448 m.
- ^ William D. Middleton: The Bridge at Quebec . Indiana University Press, 2001, ISBN 0-253-33761-5 , p. 183: Elevations of both bridges.
- ↑ Wernekke: The completion of the bridge over the St. Lawrence River in Quebec. In: Zentralblatt der Bauverwaltung. Volume 39, No. 10 (from January 29, 1919) p. 49 ( digitized version )
- ↑ Report of the Royal Commission, pp. 12, 13
- ↑ Report p. 13
- ↑ Report p. 14
- ↑ Report, p. 141
- ↑ Report p. 56
- ↑ Report p. 50
- ↑ a b Helmut Contag: The collapse of the bridge over the St. Lawrence River near Quebec (Canada). In: Zentralblatt der Bauverwaltung . Volume XXVII, No. 89 (from November 2, 1907) p. 580 ( digitized version )
- ^ Report pp. 20, 46
- ↑ Report p. 57
- ↑ Report p. 70
- ↑ Report p. 59
- ↑ Report p. 58
- ↑ Report p. 76
- ↑ Report p. 79 f
- ↑ Report p. 91
- ↑ The maximum period of 15 seconds was determined based on the distance traveled by a worker running for his life.
- ↑ Report p. 95
- ^ Henry Petroski : Engineers Of Dreams: Great Bridge Builders and the Spanning of America . Vintage 1996. ISBN 978-0-679-43939-4 .
- ↑ Report p. 5.
- ↑ Report p. 9
- ↑ Report p. 93
- ↑ See the articles in the Zentralblatt der Bauverwaltung, XXVIIth volume, by Helmut Contag in No. 89 (from November 2, 1907) p. 580 ( digitized version ), Hermann Zimmermann in No. 91 (from November 9, 1907) p. 595 ( digitized version ), Friedrich Engesser in No. 94 (from November 20, 1907) p. 609 ( digitized version), o.verf. in No. 96 (of November 27, 1907) p. 624 ( digitized version )
- ↑ See the articles in the Zentralblatt der Bauverwaltung, XXVIIIth volume, by Gottwalt Schaper: Causes of the collapse of the bridge over the St. Lawrence River near Quebec. in No. 49 (from June 20, 1908) p. 336 ( digitized version ), R. Krohn: Contribution to the investigation of the buckling strength of structured rods. in No. 84 (of October 21, 1908) pp. 559–564 ( digital copy ) and Chr. Vlachos: Considerations on the buckling resistance of barred pressure members in No. 93 (of November 21, 1908) p. 622 ( digital copy )
- ↑ Wk .: Some of the reconstruction of the bridge over the St. Lawrence River near Quebek. In: Zentralblatt der Bauverwaltung. Volume XXXI, No. 87 (from October 28, 1911) p. 538 ( digitized version )
- ^ Arthur Rohn: The accident during the construction of the bridge over the St. Lawrence River in Quebec on September 11, 1916. In: Zentralblatt der Bauverwaltung. Volume 37, No. 14 (from February 14, 1917) p. 81 ( digitized version )
- ↑ Wernekke: The completion of the bridge over the St. Lawrence River in Quebec . In: Zentralblatt der Bauverwaltung . No. 10 . Verlag Wilhelm Ernst & Sohn, January 29, 1919, ISSN 0372-8021 , p. 164 ( zlb.de ).
- ^ William D. Middleton: The Bridge at Québec . Indiana University Press, 2001, ISBN 0-253-33761-5 , pp. 164 (English, google.de ).