Single Face Wall Form

[mjmce]

Can anyone provide me with the vendor and/or product name specializing in single face wall forming?

Alternatively, does anyone have an innovative, or tried and true method for building single face formwork for an 18 ft. high wall? I am particularly interested in an ecomoncal means for design of a foundation to take out the lateral loads.

 

[Qshake]

Could you elaborate on what a single face wall form is?

 

[mjmce]

Single face wall forms are used to form concrete walls when access from only one side is available. As a result, very high overturning and lateral forces (particularly for an 18' high wall) need to be resisted by the formwork and foundation supporting the formwork.

 

[austim]

Hi, mjmce

Can you please clarify your situation a little further?

What retains the concrete on the 'far'side? eg are you concreting up near a vertical rock face (in which case can you anchor your form to it ?), or is it an adjacent building (in which case will the far wall tolerate the concreting pressures ?)

Also what is the general site geometry and ground conditions - are you working in an excavation, for example?

Site unseen - can you use a system of inclined struts (30 to 45 degrees to the vertical, founded on inclined spread footings at 'floor' level) plus vertical ground anchors close to the form (to resist the vertical components of the strut forces) ?

 

[mjmce]

austim

The excavation is 28 ft. deep and the perimeter of the excavation/pour is irregular (some walls are at 45 deg. angles). In some areas we will be pouring up against an existing concrete basement wall and at other locations we will be pouring up against a braced excavation.

Your suggestion regarding the use of inclined struts is the option originally considered; however, anchorage of the form to prevent overturning near the base of the wall and footing design for the inclined sruts to resist the high lateral forces (taken via soil passive pressure resistance and friction) is becoming costly.

I'm not sure why you suggested inclined footings for the struts (the bottom of excavation is flat). Could you explain?

 

[austim]

Hi, again mjmce.

My 'inclined footings' was personal shorthand for 'make your excavations for the strut footings wedge-shaped, with the slope perpendicular to the struts'.

With such an arrangement, you don't need to rely on friction or on lateral passive pressure, and your footing problem may be reduced considerably. You do, however, need to assess a permissible bearing capacity which allows for the inclination of the load. I seem to recall that there is/was a NAVDOCKS publication that gave advice on that.

I would address conditions at the base of the form in the same way. That is, I would have two rows of struts, (with all uplift taken in ground anchors).

 

[RiBeneke]

The most economical will probably to use internal 'lost' ties as far as possible. Anchor your ties (eg mild steel round bar) to the opposite face or concrete foundation. After concreting, cut back the ties on the face of the concrete to the cover depth and patch the holes. Across external corners you can also use diagonal ties, but make sure your forces are balanced. Where none of these will work, raking shores may be the only other solution.

 

[Qshake]

Further understanding the nature of forming I agree with RIBENEKE. Raking would be a solution to investigate and the use of interal sacrifical supports would be useful also. I have see many forms joined with interal bolts called "she-bolts" which are greased for easy removal. It is possible to use something similar but that is anchored into the solid material on the far face.

 

[jjl317]

I happen to be a design engineer in the forming industry, so I will through in my two cents without promoting our specific products. For single side wall pour, there area several manufacturers in the US that can supply what is typically referred to as an A-frame system, which is essentially a structural steel frame that is anchored down at the base to the existing concrete below the new wall to be created. A diagonal tie is either cast into the new footer below the wall to be created, or epoxied in after the fact. Of course the loads generated in this type of application are tremendous, so analysis has to be done on the footer to ensure that it can withstand the imposed loads. Manufacturers that I can think of that carry such a system - Aluma Systems, Symons, Peri, Conesco/Doka, and Safway Formwork Systems, Patent SGB(?), Ulma (?). I would recommend looking on the internet for a company with a close location, and checking with them.

 

[todousa]

Use what we call gang forms. The gang forms I've used for similar pours are made up of 8-inch double channel strongbacks on 4-foot centers with LVL 4x4 studs on 12-inch centers sheathed with 1 layer of 1-inch HDO or two layers of 3/4-inch form ply. Tie the forms back to the existing structure at spacing no greater than 4-feet OC with 3/4-inch coil rod. This will hold at a pour rate of 4-feet per hour no problem. Oh and anchor the strong backs at their bottoms extremely well. Place/strip system for a .2 Mhr/SF.
Go like heck.