Calculation of SWL on loading tower

There is a popular misconception with regards to loading towers related to their load bearing capacity.
The first thing to remember is that the load to be applied is the starting point for the design.
You should not build a tower and work backwards to find a capacity.
You most certainly not work backwards from a price to form a suitable tower!!
Loading:
1) what is the load to be applied?
2) What shape is the load? (size on plan)
3) Is the load to be applied evenly distributed across its plan dimensions?
4) How will the load arrive on your platform?
Tower:
1) What size is the tower on plan?
2) How high is the tower?
3) How do I tie the tower?
The misconception with regards load is that a given load is always applied to the tower as a UDL (Uniformly Distributed Load). The bad news is they seldom are!
For instance a Load of 10kN (1 tonne) on the tower pictured = 10kN/3.6m/1.2m=2.3kN/mSq. OK as a UDL but the reality is more likely to be a pallet weighing 10kN is placed on the scaffold by a forklift.
A standard pallet measures around 0.9m x 0.9m on plan now your load looks more like 10kN/0.9m/0.9m=12.35kN/mSq this is increased by 25% as a result of placing the load by mechanical means which now looks like 15.5kN/mSq. A considerable increase on the 2.3kN mentioned earlier.
As AxSD has stated the detail you have attached is nothing more than a sketch and as HSWT has said this would be unacceptable to any scaffolding company let alone their client base.
In Normal circumstances a loading bay is a dangerous accident waiting to happen not normally as a result of the scaffolder but as a result of the end user.
The sketch you have been provided is inadequate for the purpose and the resulting scaffold would be equally so.
I believe the front buttress to be ineffectual and is a problem waiting to happen.
I also draw attention to the fact that you are as you say looking to train drivers using this scaffold, what protects the scaffold from the learner driver?
The sketch also shows no allowance for construction in accordance with SG4.

The way forward consider the following:
1) Insist upon the drawing and calculations. It is a requirement for these to be done.
2) In the absence of a full design ask for the scaffold to be removed and a refund 
3) Advise the supplier you will have the structure looked at by the HSE, this will however restrict you from using the scaffold.
4) Get it gone and start again which is where all paths may eventually lead.
Good luck with this.
regards
Alan
 
I was gonna say that:D

---------- Post added at 03:36 AM ---------- Previous post was at 03:06 AM ----------
frederik said:
I was gonna say that:D
Click to expand...

Great advice Alan.
Was thinking how would you improve on that sketch.
Its tall so needs stabilising,kentledge or weighted kicker,plan bracing maybe,
single bay sways on 2 end bays,is tube tying front raker to buttress continious? is that how you do a buttress now?,doesnt look right, is the ledger bracing in all bays? Are the standards staggered? Perhaps screw bearer jacks in end of standard for load instead of sitting on top deck
relying on fittings.
Or build it with uc beams.Will be stronger. Still need a design tho.
 
frederik said:
I was gonna say that:D

---------- Post added at 03:36 AM ---------- Previous post was at 03:06 AM ----------



Great advice Alan.
Was thinking how would you improve on that sketch.
Its tall so needs stabilising,kentledge or weighted kicker,plan bracing maybe,
single bay sways on 2 end bays,is tube tying front raker to buttress continious? is that how you do a buttress now?,doesnt look right, is the ledger bracing in all bays? Are the standards staggered? Perhaps screw bearer jacks in end of standard for load instead of sitting on top deck
relying on fittings.
Or build it with uc beams.Will be stronger. Still need a design tho.
Click to expand...

Given a box of matches I think we could all improve that sketch
 
Alan Reade said:
There is a popular misconception with regards to loading towers related to their load bearing capacity.
The first thing to remember is that the load to be applied is the starting point for the design.
You should not build a tower and work backwards to find a capacity.
You most certainly not work backwards from a price to form a suitable tower!!
Loading:
1) what is the load to be applied?
2) What shape is the load? (size on plan)
3) Is the load to be applied evenly distributed across its plan dimensions?
4) How will the load arrive on your platform?
Tower:
1) What size is the tower on plan?
2) How high is the tower?
3) How do I tie the tower?
The misconception with regards load is that a given load is always applied to the tower as a UDL (Uniformly Distributed Load). The bad news is they seldom are!
For instance a Load of 10kN (1 tonne) on the tower pictured = 10kN/3.6m/1.2m=2.3kN/mSq. OK as a UDL but the reality is more likely to be a pallet weighing 10kN is placed on the scaffold by a forklift.
A standard pallet measures around 0.9m x 0.9m on plan now your load looks more like 10kN/0.9m/0.9m=12.35kN/mSq this is increased by 25% as a result of placing the load by mechanical means which now looks like 15.5kN/mSq. A considerable increase on the 2.3kN mentioned earlier.
As AxSD has stated the detail you have attached is nothing more than a sketch and as HSWT has said this would be unacceptable to any scaffolding company let alone their client base.
In Normal circumstances a loading bay is a dangerous accident waiting to happen not normally as a result of the scaffolder but as a result of the end user.
The sketch you have been provided is inadequate for the purpose and the resulting scaffold would be equally so.
I believe the front buttress to be ineffectual and is a problem waiting to happen.
I also draw attention to the fact that you are as you say looking to train drivers using this scaffold, what protects the scaffold from the learner driver?
The sketch also shows no allowance for construction in accordance with SG4.

The way forward consider the following:
1) Insist upon the drawing and calculations. It is a requirement for these to be done.
2) In the absence of a full design ask for the scaffold to be removed and a refund 
3) Advise the supplier you will have the structure looked at by the HSE, this will however restrict you from using the scaffold.
4) Get it gone and start again which is where all paths may eventually lead.
Good luck with this.
regards
Alan
Click to expand...


So wise :love::love::love::love:
 
This is a training tower I saw erected in East end London few years back

I dont know the price, or loadings spec.

but its to a design and all Kosher.

Its bolted to the ground and on a purpose built concrete base.

As Alan Reade says,The only problem is the end user, Well we all have to

learn.
 

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HSWT, That I do not know, but there is one at Bircham Newton the trial run? I think.

Something to do with Olympic s (funding)

Cheers
 
The loading tower was built to the design by myself and others and was struck at the start of the year for training purposes.
 
The one in Beckton park East End,It was built for tele-handler courses.
 
Well, happy new year and all that. Can anyone help if I post three scaffold sketches, 1 in East London, I in Cardiff and 1 in Cross Hands. The problems is that the drawings have no calculations for stress loads or anything and isn’t a professional drawing. The person who designed the structure is not a qualified structural engineer and not able to quantify the limit state for his calculations.
I am asking that a company look at the structure and produce a technical drawing with calculations to quantify its strength!”
 
chrbr516 said:
Well, happy new year and all that. Can anyone help if I post three scaffold sketches, 1 in East London, I in Cardiff and 1 in Cross Hands. The problems is that the drawings have no calculations for stress loads or anything and isn’t a professional drawing. The person who designed the structure is not a qualified structural engineer and not able to quantify the limit state for his calculations.
I am asking that a company look at the structure and produce a technical drawing with calculations to quantify its strength!”
Click to expand...

PM AxSD he may be able to give you a quote for the design work required
regards
Alan
 
HE'S BACK!

Sorry guys if you've missed my generally unhelpful posts. But his one I can help with...
Had a look at the dwg put up on page one then skipped all the comments to here where the problem seems to have grown? On review of the sketch - its a shocker! I know people think we over cook it but this clearly hasn't been done by a designer.

For 1.5T I would have at least expected double boards - but it is all dependent on how they intend to load it out. Following that the transoms will probably fail (by numbers - not actually fail), then the ledgers, maybe some of the fittings and so on.

I know I'd struggle to build it - scared of heights for one thing which amuses my scaffolders no end - so I don't bother - gotta ask why non-designers try to design stuff?

Try posting in the Design bit of the forum also - loads of designers in there. If that doesn't get you anywhere I can copy and paste one I did earlier and charge you £1B.

On a serious note - designs on as-builts are a nightmare - we can't throw the rules out of the window to suit the build so are you prepared to go back and fix it? We generally offer design with and without liability on as-builts depending on what we find. Some companies get very touchy about this when we list all the basic TG20 type faults...

Good luck.

IDH.
 
It's nice to know its not just us IDH who think that designs for as-builts are a nightmare....

Seriously chrbr516 you may encounter some reluctance from designers to accept that commission assuming the scaffolds are built and standing?
 
The guys are right 516,
this post started as a little advice on a loading tower now it feels like it will be condoning the errection of whatever your "Designer" sends out because someone else will say if its OK or not.
The process must always be Design and Build not Build and Design
regards
Alan
 
Thanks for all the advise guys, I've decided to go down the most costly route of obtaining new designs based on the original drawings, take down existing towers and erect new ones from the designs. That way I'll have design drawing with proper calcs and handover certs that are compliant.
 
chrbr516 said:
Thanks for all the advise guys, I've decided to go down the most costly route of obtaining new designs based on the original drawings, take down existing towers and erect new ones from the designs. That way I'll have design drawing with proper calcs and handover certs that are compliant.
Click to expand...

Thats your best move,
regards
Alan
 
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