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avondale87 wrote in post #19473916
A while ago I posted an old photo of a bridge strength test.
Here's another that didn't go to plan with the bridge wrecked and a life lost

Bendigo Advertiser, 15th May 1901
The ability of a bridge to safely carry loads was tested by driving heavy vehicles over it. At King's Bridge, a steam roller and a traction engine were used for the test - together they weighed 30 tons which was far in excess of the load limit of 25 tons.

Scroll down the following link
https://www.goldfields​guide.com.au …ocation/556/kin​gs-bridge/
During the test, one section collapsed. The traction engine fell into the creek bed, dragging Mr Boldt with it and crushing him

Photo linked from above storey

I hope they weren’t our steam rollers!
I read the link, Richard - thank you. It says the bridge had a 50 degree skew - please elaborate - as simple as possible.

avondale87 wrote in post #19473916
A while ago I posted an old photo of a bridge strength test.
Here's another that didn't go to plan with the bridge wrecked and a life lost

Bendigo Advertiser, 15th May 1901
The ability of a bridge to safely carry loads was tested by driving heavy vehicles over it. At King's Bridge, a steam roller and a traction engine were used for the test - together they weighed 30 tons which was far in excess of the load limit of 25 tons.

Scroll down the following link
https://www.goldfields​guide.com.au …ocation/556/kin​gs-bridge/
During the test, one section collapsed. The traction engine fell into the creek bed, dragging Mr Boldt with it and crushing him

Photo linked from above storey

Makes ya wonder why in the world they would test a bridge with 30 tons when that same bridge was only designed to hold 25 tons.
It looks to me like the bridge did not fail, but the driving of the rigs failed to stay on the bridge.

Inspeqtor wrote in post #19474035
Makes ya wonder why in the world they would test a bridge with 30 tons when that same bridge was only designed to hold 25 tons.
It looks to me like the bridge did not fail, but the driving of the rigs failed to stay on the bridge.

Well, Charles, if the bridge would support 30 tons it would most likely have been considered safe with its specified 25 tons - in those days - that is!
More interestingly, let’s ask Richard if he knows how they would have tested the engines boiler pressure - stand back - very well back!

Ray.Petri wrote in post #19474028
I hope they weren’t our steam rollers!
I read the link, Richard - thank you. It says the bridge had a 50 degree skew - please elaborate - as simple as possible.

Inspeqtor wrote in post #19474035
Makes ya wonder why in the world they would test a bridge with 30 tons when that same bridge was only designed to hold 25 tons.
It looks to me like the bridge did not fail, but the driving of the rigs failed to stay on the bridge.

Ray i reckon they were yours.
A skewed bridge is one where the abutments are parallel to the stream but the bridge is 'skewed' across the stream.
It puts additional stress or design requirements for the edges of the bridge as in effect they are long beams. Longer than the shorter distance across the stream at 90° to the abutments, piers.
Under-design was my thought. Designed for a straight across stream would be different for one skewed across the stream.
Looking at that photo i wondered if the deck was too far out from the supporting arch? Unsupported deck wouldn't carry same load as supported deck.

I setout the Wivenhoe rail overpass.
Had an opening of probably 6 metres or less but end or edge beams of massive proportions for such a narrow opening - 26± metres. It was a very 'skewed' bridge
Never forgot that setout
Below is aerial view and you can see how 'skewed' it is

avondale87 wrote in post #19473916
A while ago I posted an old photo of a bridge strength test.
Here's another that didn't go to plan with the bridge wrecked and a life lost

Bendigo Advertiser, 15th May 1901
The ability of a bridge to safely carry loads was tested by driving heavy vehicles over it. At King's Bridge, a steam roller and a traction engine were used for the test - together they weighed 30 tons which was far in excess of the load limit of 25 tons.

Scroll down the following link
https://www.goldfields​guide.com.au …ocation/556/kin​gs-bridge/
During the test, one section collapsed. The traction engine fell into the creek bed, dragging Mr Boldt with it and crushing him

Photo linked from above storey

And I thought that was just a comic joke:
https://www.gocomics.c​om/calvinandhobbes/198​6/11/26

Ray.Petri wrote in post #19474056
.... would have tested the engines boiler pressure....

Generally it's a hydrostatic pressure test with water to avoid the exact problem you're describing. Today's pressure vessel code puts the hydrotest pressure at 1.30x or 1.50x the Max Allowable Working Pressure. This hydro test pressure is adjusted (if needed) based on the material of construction and the Max Allowable Working Temperature. Loosely speaking, there is a further multiplier for any temperature rating above 500 F, which is the temperature when carbon steel starts to lose strength.

Pneumatic tests are still performed and have a very specific use case. Test pressure is often lowered to 1.10x and, depending on the location of the test, local law, client requirements, manufacturer requirements, or even engineer preference, stored energy calculations are performed to determine a blast radius and establish a safe distance. Leaks are identified by remote gauges and soapy water.

In some industry cases, pressure test is performed with helium because we need to be absolutely certain the joints will seal. Helium is a tiny atom and simply fits through smaller gaps in the sealing surface. Otherwise, N2 makes a good gas for pneumatic testing. But that's a different test. Hydro is for strength. Gas is for leaks.

Richard - Be curious to know if the method was different back in the day.

Cheers,

GlimmerMan wrote in post #19474089
Richard - Be curious to know if the method was different back in the day.
Cheers,

Thanks for pitching in, interesting
GM I'll let Ray answer that. I'm sure he'll give a very eloquent response to that query

Capn Jack wrote in post #19474082
And I thought that was just a comic joke:
https://www.gocomics.c​om/calvinandhobbes/198​6/11/26

Excellent

avondale87 wrote in post #19473916
A while ago I posted an old photo of a bridge strength test.
Here's another that didn't go to plan with the bridge wrecked and a life lost

Bendigo Advertiser, 15th May 1901
The ability of a bridge to safely carry loads was tested by driving heavy vehicles over it. At King's Bridge, a steam roller and a traction engine were used for the test - together they weighed 30 tons which was far in excess of the load limit of 25 tons.

Scroll down the following link
https://www.goldfields​guide.com.au …ocation/556/kin​gs-bridge/
During the test, one section collapsed. The traction engine fell into the creek bed, dragging Mr Boldt with it and crushing him

Photo linked from above storey

Interesting to read.
The method to test is direct, straightaway. Like it.

avondale87 wrote in post #19474077

Ray.Petri wrote in post #19474028
I hope they weren’t our steam rollers!
I read the link, Richard - thank you. It says the bridge had a 50 degree skew - please elaborate - as simple as possible.

Inspeqtor wrote in post #19474035
Makes ya wonder why in the world they would test a bridge with 30 tons when that same bridge was only designed to hold 25 tons.
It looks to me like the bridge did not fail, but the driving of the rigs failed to stay on the bridge.

Ray i reckon they were yours.
A skewed bridge is one where the abutments are parallel to the stream but the bridge is 'skewed' across the stream.
It puts additional stress or design requirements for the edges of the bridge as in effect they are long beams. Longer than the shorter distance across the stream at 90° to the abutments, piers.
Under-design was my thought. Designed for a straight across stream would be different for one skewed across the stream.
Looking at that photo i wondered if the deck was too far out from the supporting arch? Unsupported deck wouldn't carry same load as supported deck.

I setout the Wivenhoe rail overpass.
Had an opening of probably 6 metres or less but end or edge beams of massive proportions for such a narrow opening - 26± metres. It was a very 'skewed' bridge
Never forgot that setout
Below is aerial view and you can see how 'skewed' it is

Hosted photo: posted by avondale87 in
./showthread.php?p=194​74077&i=i67946506
forum: Nature & Landscapes

Steam boiler testing. They got big balloons Ray and blew them up. If the balloon exploded first all good. I think I got that right, it's been a long time since my apprenticeship
It would certainly make for a lot of hot air

I don't think you answered my thoughts here at all Richard.....

Ray.Petri wrote in post #19474056

Inspeqtor wrote in post #19474035
Makes ya wonder why in the world they would test a bridge with 30 tons when that same bridge was only designed to hold 25 tons.
It looks to me like the bridge did not fail, but the driving of the rigs failed to stay on the bridge.

Well, Charles, if the bridge would support 30 tons it would most likely have been considered safe with its specified 25 tons - in those days - that is!
More interestingly, let’s ask Richard if he knows how they would have tested the engines boiler pressure - stand back - very well back!

In my very limited knowledge of everything here, I have no idea what the engine boiler pressure has to do with any of this!!

avondale87 wrote in post #19474077
Ray i reckon they were yours.
A skewed bridge is one where the abutments are parallel to the stream but the bridge is 'skewed' across the stream.
It puts additional stress or design requirements for the edges of the bridge as in effect they are long beams. Longer than the shorter distance across the stream at 90° to the abutments, piers.
Under-design was my thought. Designed for a straight across stream would be different for one skewed across the stream.
Looking at that photo i wondered if the deck was too far out from the supporting arch? Unsupported deck wouldn't carry same load as supported deck.

I setout the Wivenhoe rail overpass.
Had an opening of probably 6 metres or less but end or edge beams of massive proportions for such a narrow opening - 26± metres. It was a very 'skewed' bridge
Never forgot that setout
Below is aerial view and you can see how 'skewed' it is

Hosted photo: posted by avondale87 in
./showthread.php?p=194​74077&i=i67946506
forum: Nature & Landscapes

Steam boiler testing. They got big balloons Ray and blew them up. If the balloon exploded first all good. I think I got that right, it's been a long time since my apprenticeship
It would certainly make for a lot of hot air

Thank you, Richard.

Capn Jack wrote in post #19474082
And I thought that was just a comic joke:
https://www.gocomics.c​om/calvinandhobbes/198​6/11/26

And just how did you remember that explanation Capn’. Very amusing!

GlimmerMan wrote in post #19474089
Generally it's a hydrostatic pressure test with water to avoid the exact problem you're describing. Today's pressure vessel code puts the hydrotest pressure at 1.30x or 1.50x the Max Allowable Working Pressure. This hydro test pressure is adjusted (if needed) based on the material of construction and the Max Allowable Working Temperature. Loosely speaking, there is a further multiplier for any temperature rating above 500 F, which is the temperature when carbon steel starts to lose strength.

Pneumatic tests are still performed and have a very specific use case. Test pressure is often lowered to 1.10x and, depending on the location of the test, local law, client requirements, manufacturer requirements, or even engineer preference, stored energy calculations are performed to determine a blast radius and establish a safe distance. Leaks are identified by remote gauges and soapy water.

In some industry cases, pressure test is performed with helium because we need to be absolutely certain the joints will seal. Helium is a tiny atom and simply fits through smaller gaps in the sealing surface. Otherwise, N2 makes a good gas for pneumatic testing. But that's a different test. Hydro is for strength. Gas is for leaks.

Richard - Be curious to know if the method was different back in the day.

Cheers,

Thanks Glim - nice explanation, you seem very well informed.
Isn’t helium rather expensive in the sort of quantities required?

avondale87 wrote in post #19474142
Thanks for pitching in, interesting
GM I'll let Ray answer that. I'm sure he'll give a very eloquent response to that query

Well folks - I was told that the boiler inspector would put a measuring tape around the boiler and Stoke it up to working pressure and measure the expansion - if it didn’t go bang first - that is!

Inspeqtor wrote in post #19474181
In my very limited knowledge of everything here, I have no idea what the engine boiler pressure has to do with any of this!!

Nothing at all, Charles! My brain cell was going into gyro-resonance!

Thanks for the comments and info everyone .

Ray.Petri wrote in post #19474186
Thank you, Richard.

And just how did you remember that explanation Capn’. Very amusing!

Thanks Glim - nice explanation, you seem very well informed.
Isn’t helium rather expensive in the sort of quantities required?

Well folks - I was told that the boiler inspector would put a measuring tape around the boiler and Stoke it up to working pressure and measure the expansion - if it didn’t go bang first - that is!

Nothing at all, Charles! My brain cell was going into gyro-resonance!

Thanks for the comments and info everyone .

You know words I do not know Ray!!
gyro something?!?!?!

Inspeqtor wrote in post #19474203
You know words I do not know Ray!!
gyro something?!?!?!

Something I got involved in for a short time yonks ago - fortunately the project was abandoned due to more pressing problems.

However, Resonance - regarding bridges - is a vibration which can be destructive to the bridge - for example soldiers marching across the bridge will be ordered to ‘Break Step’ to prevent the possibility of the bridge resonating which could result in collapse.
A good example of this can be seen in the link below for the Millennium Bridge in London.

https://en.m.wikipedia​.org …um_Bridge,_Lond​on#/search