Scaffolding Tie Horizontal Spacing

[anchorengineer]

The technical information from scaffold manufacturers gives you the capacity of a frame braced or tied at different tiers (vertically). The majority of scaffoldind designs that I've seen have a horizontal spacing of at least 16' (2 frame bays). Is there technical information to back this up? I don't want to be overly conservative when designing scaffolding but I need to be able to stand behind my work. Is there some horizontal rigidity assumed from adjacent tie bays? Any help is greatly appreciated.
Thanks!

Clarke Engineering Services, PC
Jobsite Engineering and Consulting

http://www.anchorengineer.com

 

[csd72]

Generally you have vertical and plan bracing that transfers the lateral loads to the support points. Every second lift and every second standard is pretty typical here in the UK.

All of the references I have are very specific for the UK.

 

[MiketheEngineer]

It also depends on the type of scaffold being used. Some have much stiffer connections than others.

Also, if the scaffold is contained it may require more.

Check out OSHA 1926.451 There are some guidelines there. Check the mfg's website - usually helpful hints there.

Configuration of the scaffold plays a big part. So does height, length and width.

VERY, VERY general recommendations are vertical diagonals every third bay and plan bracing at tie levels every third bay. Now this may vary if circular or very small bay lengths.

If this scaffold is being designed for more than light duty (25 psf live) or taller than about 50' - strongly suggest you get some experienced help.

There are 3 or 4 very good scaffolding companies here in the US. Stay away from those that don't have PEs on staff (mom and pop shops)

 

[anchorengineer]

Hi Mike,
I use the technical information provided by Waco Scaffold for allowable leg capacity. The allowable load data is given by number of frames braced/unbraced. Since they do not give horizontal distances I assume each frame needs to be braced. I'm typically going up higher than 50ft and usually have a medium duty load of 50psf. When the height dictates ties at every other frame, I tell the contractor to tie the first level at each scaffold and then alternate and stagger on the way up. That way you do not have one tower of frames without ties. Until I have technical information to tell me otherwise this is what I'm going with. It may be conservative but...

Clarke Engineering Services, PC
Jobsite Engineering and Consulting

http://www.anchorengineer.com

 

[MiketheEngineer]

My rule of thumb is every 3rd leg every third jump. That assumes moderate wind loads, no containment, all braces in place, all plank in place. Don't forget, the plank will act as small diaphragms.

We also install some plan bracing - often cheaper and quicker than multiple ties. Just use a little stronger tie.

See OSHA 1926.4501 and 451 for more info.

Good Luck