Using Acrow props as trench struts

[csd72]

I have a temporary works job where the design engineer has specified acrow props to be used as trench struts. I am used to these being used in a vertical position such as for supporting formwork or an opening but I am dubious about their capacity in a horizontal position.

Has anyone had any experience with this?

 

[civeng80]

The water authority that I used to work for used them for many years in trenching operations and they were satisfactory. I had a few problems in severe works (had 2 that completely buckled !) but generally they are quite good.

 

[csd72]

Thanks

Do you use the full rated capacity or reduce the a little for bending?

 

[civeng80]

We just used them didn't worry about designing them, it was for timbering and some trench shielding and they were about 4' long. If your designing, I would reduce the rated capacity by maybe 5 to 7% due to the bending. Other than that they are quite good for this application.

 

[csd72]

Thanks, I automatically discounted them when I saw them but i may rethink that.

 

[Ussuri]

I have seen acrow jacks used to prop trench sheeting on a number of occasions with no problem. The trenches were usually pretty small.

Used horizontally there would be an additional bending generated within the prop but I would expect this to be pretty small. The bending may induce secondary effects as the prop is not a single member as gravity would tend to to pull it to one side. Whether this is significant, not sure.

I would have though the axial loads generated by the retained material would be pretty small. Unless you had a very deep excavation and significant plant surcharge. In such cases then it is maybe more advisable to use a waling frame, or a properly designed trench shutter.

 

[csd72]

thanks ussuri and civeng80,

I cannot find anything to say definately no but I cannot find any guidance on it either. At least I know it has been done elsewhere.

 

[paulyshore]

Try

http://www.mabeysupport.co.uk/superprop.asp

for design info in both horizontal and vertical applications.
Axial/bending interaction is important for long spans.

- PR

 

[DRC1]

I would check with Acrow. Why not use trench jacks which are designed for this purpose?