Jump to content

Cold Front Today


Recommended Posts

3 hours ago, lateral said:

I have screen shots of steady 55knts with gusts to 70+ in the last three years, as I have a mooring at watchman.

No casualities on the bridge then.

I wonder if the microburst was way higher than Jays recording and very localised.

As a very frequent motorsickle riding bridge crosser I can tell you the angle at which the wind comes is often more of a worry than how much wind there is. Due to the shape of the bridge subtle changes in direction can make very significant differences to what loading vehicles see. So it is possible while it was a big gust the direction at which it hit was what did the damage more then the strength of it.

I rode over it Thursday and Friday fine .......... and didn't drop below 70kph heading to it, on it or leaving it ;) On Friday leaving the club at 8ish there was a sh*t load of traffic still backed up but 1/2 way up the northbound was a 5 Series broken down complete with a sheepish owner who could be see mouthing 'sorry' at the traffic. I did feel sorry for him as he knew he was adding to what already was a cluster f*ck.

 

Where the politics around a second crossing were sitting as of 2 weeks ago -

The current Govt and Council are a full steam ahead on a second crossing now, a billion dollars with of cycle bridge. They have put aside 390 million dollars to enable plans to be made on how to make plans to build it. They see at the end of the day the same harbour bridge plus another for push bikes and walkers, who will share it.

The Nats want to continue with the second crossing via a tunnel. Their end of project vision is a tunnel with rail (to be used as expressway buses while rail links are built to meet the tunnel) both ways and road northwards. The existing bridge then becomes 6 lanes road southward plus a push bike lane plus a walkers lane.

I suspect some politics may change today 😄

Link to post
Share on other sites

It is not my area of specialty but these steel structures have a finite life. Cyclic fatigue. Same as your mast or wire rigging in a way. Think of breaking a piece of wire by bending it constantly in the same spot. I believe the effect is a reduction in modulus and an increase in ductility, until it looses its strength. (could have my techo terms wrong there, but the stiff metal goes like a noodle)

I am curious as to the state of the remaining structural components, and if the jolt to this one piece tickled up some other pieces.

As for the pace of response, I'd be interested to see how agile NZTA can be with something like this. I wouldn't expect a peer review needed to be completed before they start fabricating a new span. If anything, they could get 2 or 3 spans underway in fabrication to different designs. 

What I am really interested in, is where the steel comes from? I assume the steel components aren't normally held in stock, but made to order for specific projects (spec of steel, size, shape, length etc). Anyone in the steel fabrication industry know what is involved in sourcing the materials to re-build this span?

Or if there is standard construction grade girders (I beam) that can be whacked in as a temporary fix while they fabricate the longer term one?

Link to post
Share on other sites
2 hours ago, Dtwo said:

Jeez why ask them when they could just get you guys to do the job.  Personally I would prefer the job to be done properly 

I'm not sure what the problem is there Dtwo.  I don't believe that anything in my reply indicated a sh*t job was acceptable, just that it seemed the engineering was already available and has been proven by father time.

Link to post
Share on other sites
2 hours ago, Steve Pope said:

In the photo of the damaged strut it showed that all the bolts on that particular plate had sheared, I would be very surprised if other bolt ups are not partially sheared as well. Not going to be a quick fix.

Apparently they are design to fail, so that the rest of the structure is not damaged. But yeah, give something a big knock, chances of some damage elsewhere are not insignificant.

Don't forget a possible outcome here is the bridge actually falling down. That would be a bit more than a few weeks inconvience ...

Bridges do fall down fairly regularly. There was that key motorway bridge in Italy that came down, with cars and trucks on it, killing people. First world, developed country and all...

 

The Morandi bridge tragedy killed 43 and left 600 homeless – but also dealt a hammer blow to Italy’s engineering legacy

https://www.theguardian.com/cities/2019/feb/26/what-caused-the-genoa-morandi-bridge-collapse-and-the-end-of-an-italian-national-myth

Link to post
Share on other sites

When the Clip-on's under went their repair. Happened to meet the Swedish engineer at Robertson park mangere.(steam trains)He reckon the repairs would only last another 10/15 yrs,that was 2009 and the main span was made from inferior metal.his recommendation was not to think about a new crossing but rather to start.

Link to post
Share on other sites

What complicates the matter is that strut is a stressed member. Fabricating a bit of steel is the easy bit, getting it in there is somewhat harder

Imagine trying to replace a spreader, and you have to get the rig tension and mast bend back to where is should (must) be, without touching the turnbuckles or addind any significant weight aloft.

Its certinaly not beyond the wit of man to complete, but considering the implications if it goes wrong the amount of planning, peer review  and analysis that goes into this will be significant

 

 

 

  • Upvote 3
Link to post
Share on other sites
9 hours ago, Romany said:

I'm not sure what the problem is there Dtwo.  I don't believe that anything in my reply indicated a sh*t job was acceptable, just that it seemed the engineering was already available and has been proven by father time.

This.  Not so much your comment but a stream of bollocks from others.  Yawn.

'Yep, too much navel contemplating, and cuzzy consulting.

Get it done, son.

I'd think that one of the pollie parties would sieze on this as an election issue.

Yes days on it would be good to think that the meetings and discussions have finished and that the fabrication to engineers drawings has commenced -it would have elsewhere in the world. Who do we ask that straight question to ?'

 

Link to post
Share on other sites

I would be rude not to acknowledge that NZTA does seem to have pulled a rabbit out of the hat. Temp repairs underway tonight is a pretty good response.

Who woulda thought that a 61 year old bridge was as technilogical as it sounds eh. I just thought it was a giant meccanno set

 

Link to post
Share on other sites

Just to preface this, I'm not a bridge, mechanical or structural engineer, so this is all best guess from heavily loaded snafus I've seen over the last 20 yrs

 

IT, you're right Its a reasonably long slender member, so it will have a bit of stretch one loaded. However,  I would guess though that the bridge structure itself has moved more that that. If Vic remade the piece to the original dimensions, when you went to install it you would probablly find it would appear to be to short ad the structure will mave likely moved away. The challenge is then to pull the structure back to the correct shape while still leaving space to install the new part and not overload anything else in the process

Link to post
Share on other sites
1 hour ago, Ed said:

Just to preface this, I'm not a bridge, mechanical or structural engineer, so this is all best guess from heavily loaded snafus I've seen over the last 20 yrs

 

IT, you're right Its a reasonably long slender member, so it will have a bit of stretch one loaded. However,  I would guess though that the bridge structure itself has moved more that that. If Vic remade the piece to the original dimensions, when you went to install it you would probablly find it would appear to be to short ad the structure will mave likely moved away. The challenge is then to pull the structure back to the correct shape while still leaving space to install the new part and not overload anything else in the process

from what I can make out this strut is in compression as part of the support truss so if this is the case stretch/elasticity would not be an issue

Link to post
Share on other sites
1 hour ago, Romany said:

But whats your point IT 🤔? Not posting uninformed opinion would be the death of ZB and -dare I say it, forums like this.

 

To be fair, this thread is in Marine talk, which is usually has quite well informed commentary.

 

Small talk on the other hand....

image.png.b361d3c61cc969a81cee97d591d7b493.png

  • Upvote 1
Link to post
Share on other sites
30 minutes ago, Ed said:

To be fair, this thread is in Marine talk, which is usually has quite well informed commentary.

 

Small talk on the other hand....

image.png.b361d3c61cc969a81cee97d591d7b493.png

Are you saying small talk is a train wreck? or are you trying to demonstrate the ductility of railway tracks?

I don't have a lot to do with steel, but I was involved in a project to install a new high pressure gas pipeline (technically I think it was medium pressure, ahem). Anyway, steel pipe will behave like a piece of spaghetti if you weld it together into a long enough string. Turns out you can drill it under and around all sorts of things. The main physical constraint is the ability to steer the drill head, which is largely to do with the geotechnical properties of the ground.

Link to post
Share on other sites

NZTA now aware that cold fronts may bring high wind gusts...

Lanes on the Auckland Harbour Bridge are being closed on Sunday morning ahead of a forecast wind shift that could see gusts of up to 90kmh.

There are currently northerly wind gusts of up to 70kmh in Auckland, but the bridge is relatively sheltered.

However, Metservice is forecasting a wind shift from the north to the west in the morning, which could bring winds of 80kmh to 90kmh.

“The wind shift could bring a swift change in the strength of the gusts, so as a precaution we will close one southbound lane and two northbound lanes on the bridge until the wind settles,” said Waka Kotahi NZ Transport Agency senior journey manager Neil Walker.

https://www.stuff.co.nz/auckland/300117484/auckland-harbour-bridge-lanes-close-as-winds-tipped-to-reach-110kmh

Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.


×
×
  • Create New...