75 Years of the Sydney Harbour Bridge
Today marks the 75th birthday of the Sydney Harbour bridge and they are expecting more then 500,000 people to flood the bridge to celebrate.
Now maybe i have just spent way to much time in dynamics and mechanics lecture but this has got me wondering about the load limit of the Sydney Harbour Bridge. Now i do understand that this figure of 500,000 people will be the total figure of people walking the length of the bridge through out the course of the entire day rather then having the whole lot on there at once, however i want to know how many people we would need to have on the bridge for it to break.
To begin my quest i had to find out a few facts about the bridge, so here they are:
| Length of arch span | 503 metres |
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| Height of top of arch | 134 metres about mean sea level |
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| Height to top of aircraft beacon | 141 metres above mean sea level |
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| Width of deck | 49 metres |
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| Clearance for Shipping | 49 metres |
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| Height of Pylons | 89 metre above mean sea level |
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| Base of each abutment tower | 68 metres across and 48 metres long (two pylons rest on each abutment tower) |
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| Total length of bridge | 1149 metres including approach spans |
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| Bearing Pins | Each of the four pins measures 4.2 metres long and 368 millimetres in diameter |
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| Thrust on bearings | Under maximum load approximately 20,000 tonnes on each bearing |
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| Number of rivets | Approximately 6,000,000 |
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| Largest rivet | Weighed 3.5 kilograms and was 395 millimetres long |
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| Longest Hanger | 58.8 metres |
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| Shortest Hanger | 7.3 metres |
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| Total weight of steelwork | 52,800 tonnes including arch and mild steel approach spans |
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| Weight of arch | 39,000 tonnes |
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| Rock excavated for foundations | 122,000 cubic metres |
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| Concrete used for bridge | 95,000 cubic metres |
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| Granite facing used on pylons & piers | 17,000 cubic metres |
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| Allowance for deck expansion | 420 millimetres |
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| Allowance for arch expansion | The arch may rise or fall 18 centimetres due to heating or cooling |
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| Number of panels in arch | 28, each 18.28 metres wide |
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| Record tonnage erected | 589 tonnes of steelwork was erected on the arch in one day on 26 November 1929 |
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| Paint required | 272,000 litres of paint were required to give the Bridge its initial three coats. |
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(Figures obtained from http://www.sydneyharbourbridge.info/)
From further research i found that when building the bridge the foundations on either side were willing to take 4 bearings each (correct me if this is wrong).
(This is an image of one of the Thrust Bearings)
So if each bearing can take a maximum of 20, 000 tonnes we are talking alot of people to make this bridge crack. We are also talking alot of math to work this out…
TBC
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