Restrained Pipe Schedule
Restrained Pipe Schedule
(OP)
I'm working on a Project where the town code is updating, and subsequently replacing all thrust blocking with restrained joints. I've done a fair amount of research on the subject, and found DIPRA's Thrust Restraint Design for Ductile Iron Pipe (and their free program) to be the best resource. Anyone who has also gone through this process, I'm sure, is well aware of how many factors go into the number of restrained joints required at various fittings/bends. So my question, does anybody have (or know of) a chart or schedule that spells this out pretty well that I could modify to fit my particular site? I'm just trying to save a little time on my end since this project was handed to me with a small budget.
As always, thanks for all the input.
As always, thanks for all the input.





RE: Restrained Pipe Schedule
1) What factor of safety do they want to use.
2) Are they going to or do they require a certain type of pipe bedding and backfill and religiously follow the requirement. If they don't the table should be designed based on the worst case trench conditions.
3) What range of pipe diameters are typical for the town.
4) Decide if you want to base your table on one maximum pressure or have different tables with values for different pressures and pipe diameters.
5) Each different fitting configuration would need to have a separate table/tables.
6) The table would need to explain the assumptions that were used so that they could be modified if necessary.
There is probably other things that need to be considered, but that is what I thought of at the moment.
Personally, I think the town is being short sighted. Thrust blocking can be an inexpensive and reliable method for handling thrust without major complications. Mechanical restraint has its place in a system, but so does concrete.
RE: Restrained Pipe Schedule
I believe the first versions of the DIPRA hard-copy thrust restraint manual (as early as 1984, and before the availability of the computer programs and downloads of same), incidentally did actually include several pages separated by soil type of required minimum restrained lengths of poly-wrapped and non-polywrapped restrained joint ductile iron pipe, for different depths of cover in increments up to 10 feet for the various soils and 90 degree horizontal bends at 100 psi. The user of these tables could then easily calculate the required restrained length for any other pressure or horizontal bend angles by a direct pressure ratio multiplier, and a separate trigonometric multiplier due to the varying bend angle. As these already voluminous tables just covered horizontal bends and did not include other thrust foci common to many jobs (such as tee branches, dead ends, vertical up bends, vertical down bends, reducers, etc.) that were however later rather easily output by the computer programs, I guess they were eventually done away with. Nevertheless, if you wanted those tables maybe photocopies of same could be provided by DIPRA or they could be contacted for better advice?