Push Pier Capacity Check Calculator

Fast checks for push piers under axial loads. Set diameters, lengths, soils, and steel quickly. See governing capacity, utilization, and pass results instantly here.

Calculator Inputs
Fields marked with * are required.
Choose units first to avoid conversion mistakes.
Match your project’s governing code requirements.
Geometry affects tip area and shaft perimeter.
For square, enter outside width.
Used for steel area and structural capacity.
Length mobilizing shaft resistance.
ASD: enter ultimate and apply FS (or set FS=1 if already allowable). LRFD: enter nominal/ultimate value.
ASD: enter ultimate and apply FS (or set FS=1 if already allowable). LRFD: enter nominal/ultimate value.
Used for structural limit state check.
Optional allowance for corrosion/section loss.
ASD: service load. LRFD: factored load.
Typical range 2.0–3.0.
Typical range 2.0–3.0.
Used with 0.60·Fy as a baseline.
Commonly 0.5–0.75 depending on method.
Often 0.9 for steel strength checks.
Output overview
The calculator checks geotechnical capacity (end + skin) and structural capacity (steel). The smaller value governs the final capacity check.
Reset
Use engineer-of-record assumptions for bearing, friction, and load factors. This tool supports preliminary screening only.
Example Data Table
Scenario Units Shape Size Length End Bearing Skin Friction Fy Applied Load Result
Residential underpin Metric (ASD) Circular 114.3 mm OD, 6.4 mm t 6.0 m 2500 kPa 40 kPa 350 MPa 200 kN PASS expected if soil governs favorably
Light commercial Imperial (LRFD) Circular 4.5 in OD, 0.25 in t 20 ft 52000 psf 850 psf 50 ksi 50 kips Depends on ϕ values and installation data
Example values are illustrative only. Always use site-specific geotechnical parameters and verified pier product properties.
Formula Used
Geotechnical resistance
  • Tip Area (circular): A = π·D²/4
  • Tip Area (square): A = B²
  • Perimeter (circular): P = π·D
  • Perimeter (square): P = 4·B
  • End resistance: Qb = q · A
  • Shaft resistance: Qs = f · (P · L)
Design checks
  • ASD geotechnical allowable: Qallow = Qb/FSb + Qs/FSs
  • LRFD geotechnical strength: ϕ·(Qb + Qs)
  • Steel area (pipe): As = π/4 · (Do² − Di²)
  • Steel area (square tube): As = Bo² − Bi²
  • Section loss: Aeff = As · (1 − r/100)
  • ASD structural allowable: Pallow = 0.60·Fy·Aeff / FSstruct
  • LRFD structural strength: ϕ·(Fy·Aeff)
  • Governing capacity: min(geotechnical, structural)
  • Utilization: Applied / Capacity
For push piers, field verification (refusal criteria, installation logs, and load testing) often governs design acceptance. Use this calculator as a screening tool alongside project specifications.
How to Use This Calculator
  1. Select Unit system and Design approach first.
  2. Choose shape, then enter diameter/width, wall thickness, and embedment length.
  3. Enter end bearing and unit skin friction from your geotechnical model or specification.
  4. Provide steel Fy from the pier product data and optional area reduction if required.
  5. Enter the applied load (service for ASD, factored for LRFD).
  6. Adjust safety factors (ASD) or resistance factors (LRFD) to match your criteria.
  7. Press Check Capacity to see PASS/FAIL, governing limit, and utilization.
  8. Use the export buttons to download a record of your inputs and results.

Capacity components that govern push piers

Push piers typically fail by soil limit, steel limit, or installation refusal. This calculator compares two controlling checks: geotechnical resistance (end bearing plus shaft friction) and structural resistance (effective steel area times yield strength). The smaller capacity governs and sets the utilization ratio.

Geotechnical inputs and expected ranges

End bearing q and unit skin friction f should come from project-specific exploration, correlations, or specifications. In granular soils, q often increases with depth, while cohesive soils may be controlled by undrained shear strength. Many projects require confirmation by installation logs or load tests, not only computed values.

Structural check and section loss allowance

The structural capacity uses an effective steel area that can be reduced for corrosion allowance or measured section loss. For thin-wall sections, small thickness changes can significantly change area and axial capacity. Use manufacturer properties for outside size, thickness tolerance, and yield strength, and apply conservative reductions where durability exposure is severe.

ASD and LRFD interpretation for field decisions

Under ASD, the calculator produces allowable capacities by dividing soil components by safety factors, then comparing to service load. Under LRFD, it applies resistance factors to combined soil resistance and to steel strength, then compares to factored load. When site criteria specify refusal pressure, stroke count, or test loads, align your factors with the specification’s acceptance method.

Example data and a quick interpretation

  • Metric (ASD): D=114.3 mm, t=6.4 mm, L=6.0 m, q=2500 kPa, f=40 kPa, Fy=350 MPa
  • Safety factors: FS(end)=2.5, FS(skin)=2.5, FS(struct)=1.67
  • Applied load: 200 kN
If utilization is ≤ 1.00, the input load is acceptable for the chosen factors. If utilization is > 1.00, reduce the applied load, increase embedment, improve soil parameters with testing, or select a stronger section. Always confirm with installation records and project criteria.
FAQs
1) What does utilization represent?
Utilization equals applied load divided by controlling capacity. Values at or below 1.00 indicate the selected model, factors, and inputs meet the check.
2) Which load should I enter for ASD and LRFD?
For ASD, enter service load. For LRFD, enter factored load. Ensure your load definition matches the project’s combination rules and documentation.
3) Can I enter allowable soil values directly?
Yes. If your end bearing or skin friction is already allowable, set the related safety factor to 1.00 so the calculator does not reduce it again.
4) Why might soil capacity govern even with strong steel?
Soil resistance depends on tip area, perimeter, and verified parameters. Weak strata, limited depth, disturbance, or conservative friction values can reduce geotechnical capacity below steel strength.
5) Does this tool cover buckling, bending, or uplift?
No. It is an axial compression screening check. Lateral loads, eccentricity, buckling, uplift, group effects, and connection details require separate design calculations.
6) How should I choose ϕ factors or safety factors?
Use the governing code, geotechnical recommendations, and project specification. Factors depend on method, data quality, testing, and reliability targets.
7) What field data should accompany this check?
Track depth, refusal criteria, pressures/stroke counts, bracket elevations, and load-test results when required. Field verification commonly controls acceptance for push pier systems.

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