Concrete Block Pipe Support

[stanier]

I am after a detail of a concrete block pipe support for a DN600 aboveground pipe in a mine environment. I have the dtails of the strap and HD Bolts. I am unsure of the reinforcing steel/concrete strength details for the block.

I only ask because this detail is but one of many items in this project. The rest I have covered. I know the first instinct is to tell me to go and hire someone. Well that isnt going to happen.

 

[Duwe6]

Depends on the bearing capacity of the 'soil' under the support, and the degree that this support restrains the pipe. The actual column can be very slender [75cm] to just support the dead-weight load. But a proper footing has to be under this support to spread the weight into the ground. Then you have to address the side loading the pipe may put on your column.

 

[BigInch]

How high is high and what is the span distributing the pipe load to that support?

If you want to be done with it, the rule of thumb is #8 at 12" c/c both ways, both faces, with 2 tie wraps at the top, but it would be somewhat irresponsible to tell you that without further details. That would usually not be an overwhelming cost to the project, allow you to do the detail and get on with the money making aspect of things. Use a steel plate on the top of the concrete, embedded in the leveling grout. Grout is usually 2 to 3" thick on top of the rough concrete level. You may want a pipe base plate with jacking screws on top of that, if attaining the precise bottom of pipe elevation is important.

 

[stanier]

Thanks for the feedback.

Soil is run of mine waste compacted for stability with a sheeps foot roller to an Rd 95%. Soil tests are carried out.

The pipe is fully welded and located on the face of the soil. The stress analysis for two conditions ambient temperature at pressure or 80C when empty and under solar radiation. Pipe movement in the axial direction is limited by embedment in soil under roads. Lateral movement is not anticipated. Supports will be partially buried in the soil to prevent lateral movement.

The pipe support is to give a nominal 400mm off the soil surface.

Rather than a steel plate offering a flat surface the type used provides a 120 degree continuous support. A 6mm membrane is installed under the pipe and apipe strap fitted to keep the support and pipe as one.

I will get a structural engineeer to check what I come up with.

 

[BigInch]

Send me a copy. I'm a registered professional structural engineer, RET. and not registered in Australia, but I'll have a look at it if you like.

 

[Duwe6]

Sounds like a 75cm concrete cylinder, with #6 rebars, spaced on 30cm centers, with the extra hoop at the top [concur w/BigInch]. Embed this column about 1/2m into the 'ground' and leave the hole open so that you have at least a 1m square [or round] opening at the foot of this column. Turn the vertical bars radially outward about 20-30cm [protrucing from the round cardboard tube, SonoTube or similar, that is used as the column form.

Puddle about 20cm of concrete in the bottom of the 1m square hole to act as a footer, and make sure that the radial turned out bars are in this pour. After the footer pour the tube full and chamfer the top edge of the concrete. Fairly simple, fairly cheap, very sturdy.

 

[rconner]

If this is steel pipe, I know there are many references for support of same mentioned e.g. in the threads at

http://www.214m.com/html/Piping fluid mechanics engineering/20080415/16837.html

and also

http://www.eng-tips.com/viewthread.cfm?qid=236443&page=64

(though I don't know if any of these get specifically into the reinforced concrete design). Beyond that, you have also of course have not noted the desired span and available pipe thickness etc., any reinforcement, nor whether the supports are to be pre-formed/fabricated or instead somehow cast around the pipes. While I am not in the pipe support nor design businesses, I will only add that I know the 1970 version of the "Welded Steel Water Pipe Manual" of SPFA at one time mentioned that at least pre-fabricated saddles should normally be formed a specific percentage slightly larger than the nominal pipe radius. While this appears to make some sense to me (e.g. to account for slight radial enlargement due to thickness of padding and/or some reasonable imperfection of pipe shapes etc.), and is also consistent with some actual pipe-on-supports research many years ago I am aware of where maximum localized stress was in fact found minimized when the saddles either fit very well or were slightly larger than the actual pipe shape involved, for whatever reason I don’t recall seeing this specific guidance in newer manuals.

 

[stanier]

Client wants these supports precast and thus the dimensions & surface finish can be tightly controlled. Therefore they will be installed on a benching and the soil recompacted around them.