New Pedestrian Bridge Engineering

[morrobay]

33 minutes ago, dallen52 said:

But we have millions of bahts worth of pedestrian crossings now.

 

Just need to educate people about what red means...

Lost cause, red lights don't stop cars, breaks do. 

[thailand49]

From the rumor the engineers aren't Thai if true is great. The tunnel had local workers but engineers design from Singapore?

[morrobay]

2 hours ago, dallen52 said:

I think I mentioned previously. 

They put the top section in place and build the steps down...

As an engineer it is interesting. 

 

Not exactly fascinating. 

But interesting, to the point where it probably falls down... ?

 

Normally ending up with a 12 inches high slab of concrete as the first step. 

It also hide the shortfalls in calculations..

No I don't see where you mentioned it previously , so now can you elaborate why it's going to fall down ? I'm only asking here because you say your an engineer. 

[dallen52]

1 hour ago, morrobay said:

No I don't see where you mentioned it previously , so now can you elaborate why it's going to fall down ? I'm only asking here because you say your an engineer. 

Various disciplines yes.Ive had an interesting working life.

Civil, Electromechanical, and systems/project management.

Wish I could still be doing.

 

I love the people who crave for more.

 

The word was probably could fall down.

Previous mention was in another topic.

 

Ok, to use structured beam concrete such as here, it could accommodate up to 250 feet length. Joined and fully compressible stressed.

Provided it was pre stressed and high grade concrete in construction. 

And built to design plan. Happy days...

Which is always a big iff,  even with overseas engineering involved. 

 

I'm not going to bore with the maths, or to go beyond saying, someone mentioned that it was three sections. Joined.?

The critical fail points would be the joins.

And the anchor method to the piers.

Two end ones only,  (if it is joined and not sat on pads).

I must observe it more closely next time I'm passing.

 

When a stressed beam is anchored, the load bearing transfers down the piers.

Making for a unilaterally load bearing structure.

Happy days, as I said before..

Makes sense to me..

 

If it's unstressed and three sections..

Just sitting on the end piers...

That's one hell of a clear span.

Speaks for itself doesn't it?

 

That's my observation anyway,  based on previous comments about three sections unstressed and joined up in the air. (Not sure how)?

 

Maybe there's more technology in there than we have seen?

[digbeth]

This bridge is steel truss I think, 

I only mentioned concrete as that concrete is usually simpler and post tensioned concrete is used everywhere now

[lapd]

It's almost definitely steel.

[dallen52]

32 minutes ago, digbeth said:

This bridge is steel truss I think, 

I only mentioned concrete as that concrete is usually simpler and post tensioned concrete is used everywhere now

Correct. 

I went and looked. 

Please retract my previous post. #36.

 

Simpler ways to calculate steel spans.

And if it is a fifty metre multiple jointed steel beams construction, it's pushing the boundaries. 

Well and truly. 

It would need to be a fabricated section beam(s) plus obvious attention to the joint methods. 

 

A quick rule of thumb is the required length of the beam is found by saying 3/4 inch of beam depth is required for every foot of beam length.

 

Let the armchair engineers chew this one over.

And I will stick with my comment about it doesn't look fit for purpose. 

I'm retired.

 

Edited September 9, 2018 by dallen52

[morrobay]

https://www.physicsforums.com/threads/opinions-on-this-50m-steel-span-bridge-without-supports.955016/

[lapd]

Took a couple pictures today.  They are somewhat hi res so you can zoom in and look at the details if you want.

 

Edited September 10, 2018 by lapd

[JimmyTheMook]

15 hours ago, dallen52 said:

 

Let the armchair engineers chew this one over.

And I will stick with my comment about it doesn't look fit for purpose. 

I'm retired.

 

 

Or some structural engineers who won't pontificate.

 

 

[KhunBENQ]

1 hour ago, lapd said:

Took a couple pictures today.  They are somewhat hi res so you can zoom in and look at the details if you want.

Thanks for that.

Finally something to seriously discuss about.

Seems all steel and the type of "zig zag" structure work is seen at many places.

Looks good.

Let's hope they will give pillars extra protection with massive guardrails/crash barriers.

 

Edited September 10, 2018 by KhunBENQ

[Gandtee]

Let's hope an unanchored crane transporter doesn't knock it off it's mountings.

[DrTuner]

1 hour ago, lapd said:

Took a couple pictures today.  They are somewhat hi res so you can zoom in and look at the details if you want.

 

The clearance is how much? All it takes is a somchai with a truck having the usual thai style load on the top..

[Spidey]

On ‎9‎/‎9‎/‎2018 at 8:41 AM, Sprigger said:

Whilst we’re on the subject of bridges forget the Suk. What’s needed here is at least 10 the length of Beach Rd. same over 2nd Rd. and several across 3rd Road. What a financial project for the authorities to get their sticky little fingers in.

The Chinese would block them by standing on them taking selfies.

[Spidey]

On ‎9‎/‎8‎/‎2018 at 5:38 PM, lapd said:

The news story on this board that said they were going to do that.

Oh well, must be true then....

 

Looks pretty permanent to me.

[Spidey]

On ‎9‎/‎7‎/‎2018 at 5:41 PM, newnative said:

     So, welds or bolts.  I think both were involved in the  deadly collapse of the walkways at the Hyatt Hotel in Kansas City years ago.   Hopefully some lessons were learned but fingers still crossed.  

You're not in Kansas now Dorothy. TiT we build things properly here.  ?

[Spidey]

2 minutes ago, Kim J said:

 Unless it gets struck by lightning or you are pushed off by your Thai GF, you will not die walking across this bridge.

A bold statement! Could become popular with people wanting to join the "Pattaya Flying Club" but living in ground floor condos.

 

I could also see it becoming popular with marauding gangs of ladyboys, looking to relieve some poor Indian of his gold chain.

[lapd]

1 hour ago, Spidey said:

Oh well, must be true then....

 

Looks pretty permanent to me.

But what if it gets knocked off like the peanut gallery here said?  Because TiT or whatever.  Even though it has been there for decades and is the same height as this bridge.

 

So I see your  and raise you 

Edited September 10, 2018 by lapd

[Spidey]

2 minutes ago, lapd said:

But what if it gets knocked off like the peanut gallery here said?  Because TiT or whatever.  Even though it has been there for decades and is the same height as this bridge.

 

So I see your  and raise you 

[newnative]

58 minutes ago, Kim J said:

You "think" welds and bolts were involved with some previous failure. What welds at what part of the structure? What bolts at what type of joint? Was it down to inadequate design or poor manufacture? If you are going to pass such comments you need to enlighten us further if it is to have any credence. If this bridge is welded together they will most likely employ a full strength butt with backing plates, which if done correctly will be stronger than the parent metal. Bolted splices which will also involve welding of plates, are as strong as you want them to be. Very basic mechanics which is bordering upon common sense tells us that the greatest shear force on the bottom chords of a simply supported girder is at the ends, diminishing to nothing at the span centre. So contrary to what you are saying the most likely place to get a shear failure will be at the end supports. The other critical factor is bending, and the maximum bending moment is at the centre of the span reducing to nothing at the ends. so these joints being at third span are not even at the maximum stressed points, so if anything fails it will be the steel member itself.

I could go on for hours but I hope just these few basic points will dispel all the myths and hysteria that are being posted. Unless it gets struck by lightning or you are pushed off by your Thai GF, you will not die walking across this bridge.

    The Hyatt failure was primarily inadequate design; the investigation after the failure determined that the walkway could barely support its own weight.  The additional weight of people on it caused it to collapse.  'If done correctly...' is probably the key phrase in your post.  Certainly one hopes that will be the case but the Florida collapse of a brand new span shows that it can sometimes be otherwise.   After recent bridge failures, and Thailand's rather lackadaisical maintenance, it's not really 'hysteria' to be discussing its rather long span without any center support.  

[ExpatOilWorker]

3 hours ago, Kim J said:

As a retired Structural Engineer now it can be seen assembled and in place it looks OK to me. When everyone go's into a shop such as Big C or Makro and there are a number of similar spanning lattice girders supporting the roof above them, which will be taking far greater loads than this bridge, do they go into panic mode? Or do they just get on with their shopping and not give the roof a thought?

All this talk about pre tensioning and post tensioning of concrete there has been. I would say you have neither I can not see any structural concrete, and doubt for loading considerations that would ever have been an option. Looks just like a simply supported steel structure with a deck.

I also did structural engineering and in one course we actually did a walk-way bridge. One of the design load criteria was to assume a Mardi Gras kind of carnival passing under the bridge and the bridge being packed with onlookers.

Then assume what would happen if a small accident happen and even more onlookers packed onto the bridge and then add 200% for safety.

This bridge does look a bit flimsy, especially if you factory in 5-10 years of rust is eating away at the initial safety factor.

Time will tell, if we hear more about it in the new in a few years.

 

 

[dallen52]

5 hours ago, Kim J said:

As a retired Structural Engineer now it can be seen assembled and in place it looks OK to me. When everyone go's into a shop such as Big C or Makro and there are a number of similar spanning lattice girders supporting the roof above them, which will be taking far greater loads than this bridge, do they go into panic mode? Or do they just get on with their shopping and not give the roof a thought?

All this talk about pre tensioning and post tensioning of concrete there has been. I would say you have neither I can not see any structural concrete, and doubt for loading considerations that would ever have been an option. Looks just like a simply supported steel structure with a deck.

I was saving the repost until I got a look at it. 

I was foot in mouth thinking concrete because the initial comment mentioned that. 

Which no way would have met the task. 

This type of construction is as you say common place and the load bearing capacity is distributed by use of the lattice spanning construction..

 

Back to my armchair..

I will wait for the visuals next time. 

[ExpatOilWorker]

14 hours ago, DrTuner said:

The clearance is how much? All it takes is a somchai with a truck having the usual thai style load on the top..

It actually look similar to the below.

 

https://www.conteches.com//knowledge-center/pdh-article-series/design-considerations-for-pedestrian-truss-bridge-structures

 

[dallen52]

2 hours ago, ExpatOilWorker said:

It actually look similar to the below.

 

https://www.conteches.com//knowledge-center/pdh-article-series/design-considerations-for-pedestrian-truss-bridge-structures

 

They normally set them at six metres with the max Thailand height signed at something like 4.5 to 5.4 metres.

And as we see often, no restriction on loading as long as its covered.

The thai road law gives the attached information. 

Maximum vehicle weight is now 53 tonnes for a multi wheel trailer combination. 

The thai road construction method does not support this type of loading.

 

(WE can all laugh, it belongs under fake news)

 

[lapd]

To all the people wanking endlessly about how it's not strong enough, it's gonna fall, its gonna get hit blah blah blah.

 

I had a close look at the Klang crossing that has been there for many years.  IT'S THE EXACT SAME DESIGN!!!  Probably the exact same height too.

 

They look different right now because the Klang crossing had a roof put on it not too long ago.  Looks like they are probably going to do the same with the new crossing, but it's the EXACT SAME DESIGN. 

 

Even the concrete stairs/supports on either side look the same.  The only difference is the new crossing is going to have elevators added because of the school for the disabled nearby.

 

 

Edited September 11, 2018 by lapd

[dallen52]

27 minutes ago, lapd said:

To all the people wanking endlessly about how it's not strong enough, it's gonna fall, its gonna get hit blah blah blah.

 

I had a close look at the Klang crossing that has been there for many years.  IT'S THE EXACT SAME DESIGN!!!  Probably the exact same height too.

 

They look different right now because the Klang crossing had a roof put on it not too long ago.  Looks like they are probably going to do the same with the new crossing, but it's the EXACT SAME DESIGN. 

 

Even the concrete stairs/supports on either side look the same.  The only difference is the new crossing is going to have elevators added because of the school for the disabled nearby.

 

 

That suits me.

The old legs ain't what they used to be. 

 

The old one was a killer, before.

 

Especially if you were getting off the airport bus with a case or two. 

 

[lapd]

1 minute ago, dallen52 said:

That suits me.

The old legs ain't what they used to be. 

 

The old one was a killer, before.

 

Especially if you were getting off the airport bus with a case or two. 

 

You are still going to be using the same crossing.  The new one with the elevator is a lot further down.  Maybe half way between Klang and Nua.

Edited September 11, 2018 by lapd

[dallen52]

3 minutes ago, lapd said:

You are still going to be using the same crossing.  The new one with the elevator is a lot further down.  Maybe half way between Klang and Nua.

Bugger.

Have to run the gauntlet of the lazy baht bus drivers who sit waiting for the airport bus..

 

At least I can leg it across the intersection to the top of klang and normal priced baht buses.

[MyFriend You]

On 9/6/2018 at 10:46 PM, Enoon said:

 

Thanks for sharing your "surprise".

 

It was fascinating.

 

Has anyone else been surprised recently?

 

 

Yeah, I found some bag worms on my wall yesterday, don;t know what to do about them, maybe I'll just leave them alone...........

[digbeth]

On 9/7/2018 at 12:51 PM, johng said:

There wasn't just one pillar that had to be reinforced,in fact I don't think the pillars where the problem

it was the bond between pillar and concrete slab.

On the subject of Thai engineering fails

here's a new build condo in Bangkok that has failed slabs that's being reinforced with more external post tensioning