Design brace? (1 Viewer)

lmk

Well-known member
Joined
Feb 14, 2011
Messages
482
Reaction score
0
2 days without a single post, so I thought I would play devils advocate a little bit by posing a quick question that came up at work and caused a bit of a stir.

Would you change the direction of a brace, ledger or sway on a design job without having to consult the designer?

Simple enough, but confusing for some.
 
Never deviate from a design, if it fails it all comes back to you. Having said that in my opinion it doesn't matter which direction bracce goes as long as its serving the purpose it's ment for.
 
Aye never deviate get the Ok from the so called experts
I remember doing a lifting frame on a crane offshore to take the crane engine out and one of the Lattice on a Unit beam was damaged when i phoned the Engineer to explain he told me to put a tube on swivels at the Lattice END OF
He was an Old School Engineer who knew the score but due to the location (offshore)and time schedule he knew the design wouldn't fail and the job needed to be done ASAP;)
 
I thought this may have received a slightly better response, especially when I've seen the same issue make some grown men weep.

The brace does the same job regardless which way it's installed, that's why we are now seeing so many designs hitting the same node point or even going in the same direction like system scaffold. In this day and age of litigation, a quick phone call to the designer would protect you though.
 
Believe or not dog leg bracing isn't as strong as bracing all going the same way but there was some decent advice never deviate away from the design are you well maximus scc
 
Believe or not dog leg bracing isn't as strong as bracing all going the same way but there was some decent advice never deviate away from the design are you well maximus scc

Iam all good SCC ,
Just busier then a one armed taxi driver with crabs ;)
 
If it fucks up the look of my scaffold it gets changed

Quite right too. I've yet to me a designer who would have a problem with it.
I suppose we all still have to cover all the bases though, so a quick call to let the guy know would be belts and braces.
 
what exactly does the ledger brace do in the scaffold ? how does the brace support the scaffold ?
 
Ok, I'll bite, but I assume this is a bit of a loaded question.

The ledger brace provides rigidity and helps transfer the weight of any imposed load to the ground.
 
In a tied scaffold, the ledger brace helps transfer any wind loads and other lateral loads between the tie points vertically. In a free-standing scaffold the ledger brace transfers any lateral loads from the scaffold to the ground. In all cases, it also provides rigidity as stated above, and triangulates the scaffold structure, strengthening the standards by reducing their effective length.

---------- Post added at 07:56 AM ---------- Previous post was at 07:52 AM ----------

Forgot to say above; changing the direction of the brace wouldn't generally make much difference in a tied scaffold, but may have a significant effect in a free-standing scaffold. The TG20:13 design guide gives some information on this. As stated by others previously, if you are changing anything on a design, it is best to check with the designer first just to make sure that everyone is covered.
 
I like your reply Biffo, can you explain the term lateral loads ? and how a ledger brace will actually reduce the effective length ?
 
OB, lateral loads just means any load that acts horizontally rather than vertically. The main one is wind, but we also add a nominal load for things like men and materials moving on the scaffold, such as a wheelbarrow. A small horizontal load is also applied to the brace by the standard to restrain it (2.5% of the vertical load generally). In terms of the effective length the easiest way to explain it is for an independent with 2.0m lift heights that is ledger braced every alternate bay; for the calculations, the ledger braced frame has an effective lift height of 2.0m but the frame without ledger bracing has an effective lift height around 3.2m (depending on tie spacing). This means that the non-ledger braced frame is far weaker than the one with the ledger brace. This is generally why heavily loaded design jobs have more bracing than standard scaffolds.
 
In a tied scaffold, the ledger brace helps transfer any wind loads and other lateral loads between the tie points vertically. In a free-standing scaffold the ledger brace transfers any lateral loads from the scaffold to the ground. In all cases, it also provides rigidity as stated above, and triangulates the scaffold structure, strengthening the standards by reducing their effective length.

---------- Post added at 07:56 AM ---------- Previous post was at 07:52 AM ----------

Forgot to say above; changing the direction of the brace wouldn't generally make much difference in a tied scaffold, but may have a significant effect in a free-standing scaffold. The TG20:13 design guide gives some information on this. As stated by others previously, if you are changing anything on a design, it is best to check with the designer first just to make sure that everyone is covered.

Spot On :)
 
Okay, whilst we have the designers interest, do you fancy having a go at explaining why exactly going over to over is tension and under to over is compression? I know we have to do it, I know when we have to do it, but for the life of me, I can't figure out why. I get the compression thing better, like the plan brace to opposite sides but what exactly changes when it's over to over.
 
Imk, I'm not sure what you mean by "over to over" and "under to over"; do you mean that the brace is over the bottom tube and under the top tube that it's connected to? The main reason for doing this is to get a better angle on the brace, but it makes no difference whether the brace is in tension or compression. For a raker supporting vertical load, the tube wants to be as close for vertical as possible, and for a brace supporting mainly horizontal forces, such as a sway brace or ledger brace, it wants to be as close to horizontal as possible, but an angle between 35 to 55 degrees is preferred to enable the brace to support any uplift or tension forces on the standard as well as horizontal loads. For a double, the way that the coupler is orientated makes no difference to its strength.
 
That surprises me, I knew the double has the same strength which ever way but I always believed to set a tube in tension the pull back would have to be set over the top of the horse ledger and over the top of the ledger it was supporting. Setting a spur in compression from below would be under the top ledger it was supporting and over the top of the ledger it was punched from. Funny how you can carry a misconception for years.
 
That surprises me, I knew the double has the same strength which ever way but I always believed to set a tube in tension the pull back would have to be set over the top of the horse ledger and over the top of the ledger it was supporting. Setting a spur in compression from below would be under the top ledger it was supporting and over the top of the ledger it was punched from. Funny how you can carry a misconception for years.

I think you need to separate the difference between braces, pull backs & spurs.

your brace would normally be a two directional member, both T&C whereas a pull back is normally only in tension and a spur is normally in compression. Braces should be considered a general task member as opposed to the specific requirements of either the spur or pull back.

The over under location of the fitting on any of the above would normally be related to what they will be getting in the way of as opposed to their structural capacity.
 
Thanks for your explanation guys, every day is a school day.
 
Top Bottom