Auckland Harbour Bridge hit by truck 3

[Agent666]

A couple of days ago in freak wind gust (120km/hr reported) a truck tipped over and hit one of the diagonal struts on the Auckland Harbour Bridge shearing off the bolts and causing structural damage to the strut.

Another truck was tipped over onto the median barrier.

https://youtu.be/8uBfru1SZ08

https://www.newshub.co.nz/home/new-...auckland-harbour-bridge-caught-on-camera.html

They closed the centre 4 lanes, effectively going from 5 peak hour lanes to 2. Bridge is the only harbour crossing to the north shore of Auckland.

Several weeks to fix permanently apparently, a temporary fix was done last night. Which as I understand it will enable an additional lane to open each way.

Traffic has been a nightmare! 3 times longer journey times if you're trying to cross or go the long way round.

 

[hokie66]

I think those engineers know what they are doing, but I wish they would stop saying a strut is in tension.

 

[Agent666]

Mainstream media were calling it a beam for the first few days.... So I'll take strut any day.

 

[hokie66]

A strut is a compression member. If it is supposed to take tension, they should call it a tension member or tension tie. There is no excuse for kowtowing to the mainstream media.

 

[davidbeach]

So then provide the citation where faux got it right.

 

[human909]

I'll take strut. Terminology various even within the engineering field both within regions and even more so across regions. I don't think there is benefit of being pedantic about the precise terminology of members is important if it doesn't affect the design or construction.

You can find countless sources referring to struts taking tension from general vernacular to scholarly articles.

https://en.wikipedia.org/wiki/Strut

https://scholar.google.com/scholar?hl=en&as_sdt=0,5&q="tension+strut"&btnG=

From my perspective a tie is designed to carry tension and can often not carry appreciable compression. As strut can be either. The is a Warren Truss with vertical ties. In my terminology I'd be calling all the diagonals struts. But that's me. I'm not a bridge engineer.

Likewise I've heard some academics refer to single story portal frame columns as beams as their main function is to resist bending rather than vertical load. Again by many definitions this is entirely correct. Though I'm sure it would confuse a lot of people on site if I started referring to that vertical steel member as a beam.

 

[hokie66]

davidbeach,

It is similar to expressing current in Ohms.

 

[human909]

davidbeach,

It is similar to expressing current in Ohms.

Really? Really?

Current is extremely well defined.

The nomenclature of a structural member is not. They are often, but not always, defined by their expected function. But many member have multiple functions. Some members more commonly defined by their orientation. If you can give me a clear definition unambiguous of the even a dozen member types I would be impressed, even the basics of beams and columns are not clear cut.

 

[hokie66]

We'll have to agree to disagree. I will just continue to try to maintain the structural language as taught to me.

 

[Retrograde]

I'm with human909 - a strut can take tension.

 

[hokie66]

The damage is to a truss web member. It looks like a modified Warren truss. One engineer just said the damage was to a tension member, the other said it was to a strut.

In truss terminology, we just call them tension and compression web members. The terms strut and tie are normally not used for trusses.

 

[hokie66]

Tried to find a comprehensive glossary of structural engineering terms. One source is "Dictionary of Architecture and Construction", by Cyril M. Harris.

The definition he gives is "a brace or any piece of a frame which resists thrusts in the direction of its own length, may be upright, diagonal, or horizontal."

Sure there are members which are capable of taking tension or compression due to load direction reversal, but I don't think that applies to this bridge web member.

 

[human909]

The definition he gives is "a brace or any piece of a frame which resists thrusts in the direction of its own length, may be upright, diagonal, or horizontal."

And there in lies the complexities. By that definition a column would be a brace. (I wouldn't use that definition, but nor would I say that definition is 'wrong'.) Personally I use the term brace or bracing to any thing that is designed to resists lateral movement of a structure (as a load that is 90degrees to the direction of gravity).

Sure there are members which are capable of taking tension or compression due to load direction reversal, but I don't think that applies to this bridge web member.

But that is the point isn't it. Unless your definition of a strut precludes members that are never in tension then I don't see the issue.

My point is member nomenclature varies so much that you can't be overly pedantic about it. As long as there is adequate and clear communications then we can all be happy. Like all good communication, being aware of your audience is important. Terms I might use to other engineers might make no sense at all to site contractors.

 

[hokie66]

First quote you listed: That says that a brace which resists thrust is a strut. It doesn't say a column, which resists thrust, is a brace. But a column is a strut, so the definition fits.

Second quote you listed: Of course a strut can take tension. Compression is almost always more critical than tension because of buckling, as long as the connections allow.

Terminology is important. Calling a footing a 'footer', and calling concrete 'cement' are just wrong, as is calling a primarily tension member a strut.

 

[human909]

Your rigid belief in the righteousness of your own definitions of member terminology doesn't aid communication, it hinders it. Clear communication is the important part, this sometimes requires precise terminology, sometimes it doesn't.

 

[hokie66]

I'll take that as constructive cricism. Obviously, my communication skill in this instance has been wanting.

 

[human909]

I'll take a step back from the discussion after this..

Embarrassingly and ironically it seems to be me who miscommunicated. That wasn't meant to be criticism towards you, though I certainly did phrase it forcefully (oops). I don't believe your communication skills in "this instance have been wanting". We simply have disagreed and I think I miscommunicated in my last post. My previous post was just meant to highlight the role that precise terminology can play in communication and that it isn't always necessary.

Anyway we are off topic. Hokie66 your contributions to this site are extensive and productive. We just disagree on this minor point.

 

[Eufalconimorph]

Truck hit big metal thingy. Big metal thingy bend. Bending make big metal thingy pull really hard on lot of small metal grippy sticks. Grippy sticks break. Bad, very dangerous.

 

[zeusfaber]

 

[human909]

That was the first thing I though of when I read that sentence. For those who haven't seen it. Here is the blueprint for the Saturn 5 Rocket, otherwise known as the Up Goer Five.

https://xkcd.com/1133/