Tower anchers, screw in

[tower22]

Can any one tell me how much torque in FT/LBS does a screw in pile take to hold up a 96 ft free standing tower. I think I will use a 3 in. pipe with a 14 in. plate.Tower has 3 Legs 49 in. apart. Would a person be wise to set the piles 8 ft. apart and frame them then set tower on top or just put them at 49 inchs apart.

 

[jdonville]

tower22,

1) Get a structural engineer to analyze loads

2) Get a geotechnical engineer to give you recommendations for foundations in general and screw-in piles in particular.

Depending on the pile/anchor system and the subsurface conditions, the amount of torque could vary. Also, not all screw-in systems are created equal. You should consider load testing to ensure that the recommended solution works.

Jeff


Jeffrey T. Donville, PE
TTL Associates, Inc.

http://www.ttlassoc.com

 

[tower22]

Thanks Jeff.
WE are doing alot of sites. I thought if we set a 5000 ft/lbs of torque plus min. of 9 feet would work or do we need to analyze each site ?

 

[BigH]

tower22 - to analyze each and every site - that is always the golden question. A lot depends on the geology of the area in which you are working. There are many places where the basic soil conditions, say 1.5m or 5 ft below surface are remarkably the same over very large areas - bad areas are usually known. Then there are sites where the conditions can change every hundred feet or less. I would do a desk search of the geology of your area of interest; check out ag maps or US conservation maps for details. Your geotechnical engineer should know if your alignment is "always good" - "often bad" or "this and that." He would be able to help you arrange for a realistic programme of investigation. In more uniform areas, you could space out the investigation, in poor areas, you may very well have to do an investigation at each site. But get the geotechnical guy on board as part of your planning and I would surmise the overall design experience will be greatly enhanced.

 

[eric1037]

When I worked in the power industry, the standard was to perform at least one soil boring at each structure. If the structure was large, we did more than one.