Bolting Acrow props together 1

[ma701ss]

Hi,

A contractor has proposed propping above a first floor bay window from the outside whilst the bay window is replaced. The floors cannot be propped internally so he’s suggested bolting two Acrow props together, one on top of the other, in order to reach 5.2m height (size 4 Acrow extends only to 4.8m). Seems unlikely to be secure, is this typically ever done? If not, would appreciate possible solutions that I can discuss with them.

Thanks

 

[r13]

You better to provide a sketch for people to understand your situation. I've no clue what is this about - Acrow Prop?

 

[ma701ss]

Sorry, I presume in that case you’re not based in the UK. This may help to explain what an Acrow prop is, and sizes:

https://www.constructionproductsonline.co.uk/acrow-props

 

[LittleInch]

Cant he just weld a scaffold pole to it?

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[ma701ss]

Don’t really think that’s practical!

 

[r13]

Provide a flat, sturdy working platform with height > 40cm. I remember someone has asked "strong boy", but not aware there is another name for this shoring device

 

[ma701ss]

Strongboys fit onto Acrows to support loads that are not directly above the Acrow.

Not sure what a suitable platform would be, presumably it would need to be solid concrete, etc.

 

[Ceinostuv]

Bolting props together is not uncommon; however, testing shows (and this can be intuited by putting a little thought into unbraced heights and the fact you have introduced a potential hinge), the capacities will be much lower than using a single prop. Most of the big formwork/shoring/scaffolding companies, like PERI and Meva, have literature about stacking props and, iirc, will require at least a single prop tower be erected in order to use the stacked prop loads. I’ve never worked with Accrow products though so I don’t know what kind of literature they might have about this.

Judgement-In-Training

 

[Tomfh]

Absolutely not.

Acro props work as pin ended struts.

Even if the new connection was rigid it would be too slender.

 

[r13]

For temporary use, provide thick layers of plywood board beneath cast in place solid concrete block will do. The wood board is to spread the load evenly to the ground and prevent settlement. Don't splice manufactured shoring device, unless specifically permitted by the manufacture. Secure the top of the bay window, which is the source of any hazard situation, throughout the installation.

 

[ma701ss]

Thanks for the replies. As suspected, not a good idea, so will need to consider a suitable platform and use size 4 Acrow props. Plywood doesn’t seem like a practical solution as approx. 40 layers would be required. Depending on the load, which should be relatively light, perhaps a number of stacked 7N concrete blocks would be suitable.

 

[r13]

Only a few layers of plywood should be rigid enough, it acts as the base slab of a spread footing, not stack the wood to 40cm, maybe 5-10cm is suffice. Precast concrete block can be fine, if stable. Note that even a slight movement can have severe consequence.

 

[MIStructE_IRE]

Frightening that this is even being considered. Imagine the buckling?!!

 

[Ceinostuv]

STACKING PROPS IS COMMON PRACTICE (admittedly, I don't know if the props being asked for in this specific post are appropriate for stacking, though)

I would never try to determine the capacities myself but can you imagine if the field had to erect an entire scaffold system for every clerestory, bridge, or any other scenario with an extremely elevated slab? Erection of the shoring alone would kill budgets everywhere and the options for drive lanes below shored floors would be severely limited.

https://www.ulmaconstruction.com/en/formwork/props-shoring-systems/props/aluminium-prop-aluprop

https://www.peri-usa.com/products/a...g/shoring/multiprop-aluminium-slab-props.html

I'm not saying its appropriate for this scenario, but the question of "Can I stack props?" is not a definitive "No."

Judgement-In-Training

 

[Tomfh]

Consider bigger longer props. Acro at 5m is really pushing it.

 

[ma701ss]

Tomfh the largest prop is size 4 (4.8m) so it would need to be on a platform or, as you say, a larger prop, but what other options are there? This is a small domestic project to replace a bay window at first floor level. Just to repeat the original post that propping floors internally isn’t an option, only external propping.

 

[r13]

Ceinostuv,

Unless you can provide worked example, otherwise I would say the statement is false. We know that typical scaffolding is designed to be stackable, and some are height adjustable to the desirable elevation. It is not unusual to see wood/concrete blocks under the scaffold legs for light duty use, so to makeup a few inches, if it is must be level. In this case, one segment is 4.8m, two of them will be 9.6m, that obviously would require bracing, which potentially will be blocking the available working space, and endanger the operation that requires a lot of maneuver.

 

[ma701ss]

The overall height is 4.8m (not 9.6m), just to clarify, so 2x size 1 Acrow props would be used if they were bolted together.

 

[Ceinostuv]

retired13,

I'm not sure I understand what you're saying. What statement would you say is false?

For further clarification, do you recognize a difference between shoring props and scaffolds?

Nowhere in my posts did I imply that (2) Acrow 4's would need to be stacked; a 0 and 4 would work, if only heighth-wise (not necessarily strength-wise).

By the way, I agree completely with your statement

Don't splice manufactured shoring device, unless specifically permitted by the manufacture.

and my intention was to convey that there are manufacturers who provide that specific permission. Before your latest post, I considered us to be in agreement.

Judgement-In-Training

 

[dhengr]

Ma701ss:
You say nothing about the make-up of the bldg. structure or cladding, a wall cross section and elev. view around the window would help a lot. How close to the exterior wall can the ‘size 4 Acrow’ post be, distance away from the bldg? Start with the top/cap pl. on the post at about 4.6m for some remaining adjustability. Take a light WF beam, long enough to span vertically from the 4.6m elev. and up, past the framing at the 1st fl. ceiling and second fl. framing, and up to the framing above the 2nd fl. ceiling. These beams/struts, are bolted and keyed into the ext. wall as needed, certainly at the two main framing/diaphragm levels. Weld a horiz. cantilever to the bot. of these struts, canti. out abt. 1.5’ (distance away from the bldg.) to be supported on the Acrow post. Provide a kicker from the end of this horiz. canti. up to some elev. on the strut (maybe the 2nd fl. ceiling level) such that the reactions from the strut can be dealt with in the ext. wall. You may want some lateral support on these struts and at the bot. 1.5’ canti.