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HelixPro Design Software
Serving IA including the Greater Des Moines area
Our Iowa Service Area
Cities in Adair County, IA
Adair
Bridgewater
Fontanelle
Greenfield
Orient

Cities in Appanoose County, IA
Centerville
Cincinnati
Exline
Moravia
Moulton
Mystic
Plano
Udell
Unionville

Cities in Boone County, IA
Boone
Boxholm
Luther
Madrid
Ogden
Pilot Mound

Cities in Butler County, IA
Allison
Aplington
Aredale
Austinville
Bristow
Clarksville
Dumont
Greene
Kesley
New Hartford
Parkersburg
Shell Rock

Cities in Cerro Gordo County, IA
Clear Lake
Dougherty
Mason City
Meservey
Plymouth
Rock Falls
Rockwell
Swaledale
Thornton
Ventura

Cities in Clarke County, IA
Murray
Osceola
Woodburn

Cities in Dallas County, IA
Adel
Booneville
Bouton
Dallas Center
Dawson
De Soto
Dexter
Granger
Linden
Minburn
Perry
Redfield
Van Meter
Waukee
Woodward

Cities in Davis County, IA
Bloomfield
Drakesville
Floris
Pulaski

Cities in Decatur County, IA
Davis City
Decatur
Garden Grove
Grand River
Lamoni
Leon
Van Wert
Weldon

Cities in Floyd County, IA
Charles City
Colwell
Floyd
Marble Rock
Nora Springs
Rockford
Rudd

Cities in Franklin County, IA
Alexander
Bradford
Geneva
Hampton
Latimer
Popejoy
Sheffield

Cities in Greene County, IA
Churdan
Cooper
Dana
Grand Junction
Jefferson
Paton
Rippey
Scranton

Cities in Grundy County, IA
Beaman
Conrad
Dike
Grundy Center
Holland
Reinbeck
Wellsburg

Cities in Guthrie County, IA
Bagley
Bayard
Casey
Guthrie Center
Jamaica
Menlo
Panora
Stuart
Yale

Cities in Hamilton County, IA
Blairsburg
Ellsworth
Jewell
Kamrar
Randall
Stanhope
Stratford
Webster City
Williams

Cities in Hancock County, IA
Britt
Corwith
Crystal Lake
Garner
Goodell
Kanawha
Klemme
Woden

Cities in Hardin County, IA
Ackley
Alden
Eldora
Garden City
Hubbard
Iowa Falls
New Providence
Radcliffe
Steamboat Rock
Union
Whitten

Cities in Humboldt County, IA
Renwick

Cities in Jasper County, IA
Baxter
Colfax
Ira
Kellogg
Killduff
Lynnville
Mingo
Monroe
Newton
Prairie City
Reasnor
Sully

Cities in Keokuk County, IA
Delta
Gibson
Harper
Hayesville
Hedrick
Keota
Keswick
Martinsburg
Ollie
Richland
Sigourney
South English
Thornburg
Webster
What Cheer

Cities in Kossuth County, IA
Algona
Bancroft
Burt
Fenton
Lakota
Ledyard
Lone Rock
Swea City
Titonka
Wesley
Whittemore

Cities in Lucas County, IA
Chariton
Derby
Lucas
Russell
Williamson

Cities in Madison County, IA
Bevington
Earlham
Macksburg
Patterson
Peru
Saint Charles
Truro
Winterset

Cities in Mahaska County, IA
Barnes City
Beacon
Cedar
Fremont
Leighton
New Sharon
Oskaloosa
Rose Hill

Cities in Marion County, IA
Bussey
Columbia
Hamilton
Harvey
Knoxville
Melcher Dallas
Otley
Pella
Pleasantville
Swan
Tracy

Cities in Marshall County, IA
Albion
Clemons
Gilman
Haverhill
Laurel
Le Grand
Liscomb
Marshalltown
Melbourne
Rhodes
Saint Anthony
State Center

Cities in Mitchell County, IA
Little Cedar
Mc Intire
Orchard
Osage
Saint Ansgar
Stacyville

Cities in Monroe County, IA
Albia
Lovilia
Melrose

Cities in Polk County, IA
Alleman
Altoona
Ankeny
Berwick
Bondurant
Clive
Des Moines
Elkhart
Grimes
Johnston
Mitchellville
Pleasant Hill
Polk City
Runnells
Sheldahl
Urbandale
West Des Moines
Windsor Heights

Cities in Poweshiek County, IA
Brooklyn
Deep River
Grinnell
Guernsey
Hartwick
Malcom
Montezuma
Searsboro

Cities in Ringgold County, IA
Benton
Diagonal
Ellston
Kellerton
Mount Ayr
Redding
Tingley

Cities in Story County, IA
Ames
Cambridge
Collins
Colo
Gilbert
Huxley
Kelley
Maxwell
Mc Callsburg
Nevada
Roland
Slater
Story City
Zearing

Cities in Tama County, IA
Buckingham
Chelsea
Clutier
Dysart
Elberon
Garwin
Gladbrook
Lincoln
Montour
Tama
Toledo
Traer
Vining

Cities in Union County, IA
Afton
Creston
Cromwell
Lorimor
Shannon City
Thayer

Cities in Wapello County, IA
Agency
Blakesburg
Chillicothe
Eddyville
Eldon
Kirkville
Ottumwa

Cities in Warren County, IA
Ackworth
Carlisle
Cumming
Hartford
Indianola
Lacona
Liberty Center
Martensdale
Milo
New Virginia
Norwalk
Prole

Cities in Wayne County, IA
Allerton
Clio
Corydon
Humeston
Lineville
Promise City
Seymour

Cities in Webster County, IA
Burnside

Cities in Winnebago County, IA
Buffalo Center
Forest City
Lake Mills
Leland
Scarville
Thompson

Cities in Worth County, IA
Fertile
Grafton
Hanlontown
Joice
Kensett
Manly
Northwood

Cities in Wright County, IA
Belmond
Clarion
Dows
Eagle Grove
Galt
Goldfield
Rowan
Woolstock

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Commercial Helical Anchors / Tiebacks

Helical Anchors (also referred to as tiebacks) provide lateral stability to foundation walls and retaining walls with unbalanced earth pressures. Helical anchors can be installed with hand-held equipment, mini-excavators, skid steers, backhoes, trackhoes, or crane-supported rigs so the anchors can be installed in almost any application. This versatility, along with the ability to immediately load and test the anchors, make helicals a convenient and economical solution for a wide variety of projects. helical tiebacks in Iowa

ADVANTAGES

  • Predictable capacity
  • Helix blade configuration selected to achieve design embedment and capacity
  • All-weather installation
  • Can be installed in areas of limited or tight access
  • Installation does not generate spoils
  • Clean installation with no messy grout
  • Load tests can be performed immediately following installation
  • Available with optional hot-dip galvanizing for added corrosion protection

Design Considerations

Helical anchors are a factory-manufactured steel foundation system consisting of a central shaft with one or more helix-shaped bearing plates, commonly referred to as blades, welded to the lead section. Extension shafts, with or without additional helix plates, are used to extend the anchor into competent load-bearing soils. Helical anchors are advanced ("screwed") into the ground with the application of torque.

The terms helical piles, screw piles, helical piers, helical anchors, helix piers, and helix anchors are often used interchangeably by specifiers. However, the term "pier" more often refers to a helical foundation system loaded in axial compression, while the term "anchor" more often refers to a helical foundation system loaded in axial tension.

Model 150 Helical Anchor System

  • Outer Dimensions = 1.50" x 1.50"
  • Anchor Shaft Yield Strength = 90 ksi (min.)
  • Coupling Hardware: ¾" Grade 8 Bolt with Nut
  • Available Helix Blade Diameters = 6", 8", 10", 12" and 14"
  • Helix Blade Thickness = 0.375"
  • Termination Hardware: 1" Threaded Rod, Tensile Strength = 120 ksi (min.)

-- View Our Helical Anchors and Tiebacks Product Specifications document --

Model 175 Helical Anchor System

  • Outer Dimensions = 1.75" Round Corner Square Bar
  • Anchor Shaft Yield Strength = 90 ksi (min.)
  • Coupling Hardware: (2) ¾" Grade 8 Bolt with Nut
  • Available Helix Blade Diameters = 6", 8", 10", 12" and 14"
  • Helix Blade Thickness = 0.375"
  • Termination Hardware: 1" Threaded Rod, Tensile Strength = 120 ksi (min.)

-- View Our Helical Anchors and Tiebacks Product Specifications document --

Capacities Summary
 

Maximum Allowable Mechanical Shaft Capacities (3,5)

 

Default Torque Correlation Factor (6) Kt (ft-1)

Maximum Installation Torque (ft-lbs) Maximum Ultimate Torque Correlated Soil Capacity (6,7)Qu = Kt X T
(kips)
Axial Compression (kips) Axial Tension (kips)

HA150

10

6,500

65.0(8)

26.5(1,8)

26.5(1)

HA175

10

10,000

100.0(8)

65.7(8)

53.0(1)

HP287

9

5,600

50.4

46.4(4)

23.6(2)

HP288

9

7,900

71.1

65.4(4)

34.1(2)

HP349

7

13,000

91.0

88.7(4)

50.8(2)

HP350

7

16,000

112.0

107.8(4)

62.5(5)

  1. Governed by AISC allowable capacity of single Ø3/4" (HA150) or (2) Ø3/4" (HA175) Grade 8 bolt(s) in double shear.
  2. Governed by bearing at the bolt holes.
  3. Capacities include a scheduled loss in steel thickness due to corrosion for black, uncoated steel. Scheduled thickness losses are for a period of 50 years and are in accordance with ICC-ES AC358.
  4. Allowable compression capacities are based on continuous lateral soil confinement in soils with SPT blow counts  ≥ 4.Piles with exposed unbraced lengths or piles placed in weaker or fluid soils should be evaluated on a case by case basis by the project engineer.
  5. Listed mechanical capacities are for the shaft only. System capacities should also not exceed the installed torque correlated capacity or those listed in the respective bracket capacity tables.
  6. Listed default Kt factors are widely accepted industry standards. They are generally conservative and are consistent with those listed in ICC-ES AC358. Site-specific K t factors can be determined for a given project with full-scale load testing.
  7. Soil capacities listed are ultimate values at maximum installation torque. Allowable soil capacity values are obtained by dividing the ultimate values by the appropriate factor of safety (FOS). FOS is most commonly taken as 2.0, although a higher or lower FOS may be considered at the discretion of the helical pile designer or as dictated by local code requirements.
  8. Square shaft piles may be considered for compression applications in soil profiles that offer sufficient continuous lateral support; e.g., in soils with SPT blow counts ≥ 10. Even in these higher strength soil conditions, buckling analysis should be considered, taking into account discontinuities and potential eccentricities created by the couplers

Determination of Capacity

The ultimate capacity of a helical anchor may be calculated using the traditional bearing capacity equation:

Qu = ∑ [Ah (cNc + qNq)]

Where:
Qu = Ultimate Anchor Capacity (lb)
Ah = Area of Individual Helix Plate (ft2)
c = Effective Soil Cohesion (lb/ft2)
Nc = Dimensionless Bearing Capacity Factor = 9
q = Effective Vertical Overburden Pressure (lb/ft2)
Nq = Dimensionless Bearing Capacity Factor

Total stress parameters should be used for short-term and transient load applications and effective stress parameters should be used for long-term, permanent load applications. A factor of safety of 2 is typically used to determine the allowable soil bearing capacity, especially if torque is monitored during the helical anchor installation.

Determiniation of Capacity

Like other deep foundation alternatives, there are many factors to be considered in designing a helical anchor foundation. Foundation Supportworks recommends that helical anchor design be completed by an experienced geotechnical engineer or other qualified professional.

Another well-documented and accepted method for estimating helical anchor capacity is by correlation to installation torque. In simple terms, the torsional resistance generated during helical anchor installation is a measure of soil shear strength and can be related to the bearing capacity of the anchor.

Qu = KT

Where:
Qu = Ultimate anchor Capacity (lb)
K = Capacity to Torque Ratio (ft-1)
T = Installation Torque (ft-lb)

The capacity to torque ratio is not a constant and varies with soil conditions and the size of the anchor shaft. Load testing using the proposed helical anchor and helix blade configuration is the best way to determine project-specific K-values. However, ICC-ES AC358 provides default K-values for varying anchor shaft sizes, which may be used conservatively for most soil conditions. The default value for the Model 150 Helical Anchor System (1.50" square shaft) is K = 10 ft-1.

-- View Our Helical Anchors and Tiebacks Product Specifications document --

 

Helix Blade Geometry

Helix Blade Geometry

Foundation Supportworks' helical anchors feature blades manufactured with a true helix shape conforming to the geometry criteria of ICC-ES AC358. The leading and trailing edges of true helix blades are within one-quarter inch of parallel to each other and any radial measurement across the blade is perpendicular to the anchor shaft. A true helix shape along with proper alignment and spacing of the blades is critical to minimize soil disturbance during installation.

Conversely, blades that are not a true helix shape are often formed to a 'duckbill' appearance. These plates create a great deal of soil disturbance and do not conform to the helix geometry requirements of ICC-ES AC358 since their torque to capacity relationships are not well documented.

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