| Scenario | Force | Area | Pressure | Design pressure (SF=1.30) |
|---|---|---|---|---|
| Jack pad on steel plate | 120 kN | 0.040 m² | 3000 kPa | 3900 kPa |
| Temporary bearing block | 35 kN | 0.025 m² | 1400 kPa | 1820 kPa |
| Small circular pad | 10 kN | Ø 150 mm | 566 kPa | 736 kPa |
- Force (from mass): F = m × g
- Area: A = w × h (rectangle), A = π(d/2)² (circle), A = (π/4)(D² − d²) (annulus)
- Pressure: P = (F × LF) / A
- Design pressure: Pd = P × SF
- Equivalent head: h = Pd / (ρ × g)
- Select a calculation method: enter a force, or enter mass with gravity.
- Pick the face geometry and enter the required dimensions.
- Set the load factor and safety factor used by your workflow.
- Optionally enter an allowable pressure to get a pass/fail utilization.
- Click Calculate, then export CSV or PDF if needed.
Face Pressure Guide for Construction Use
1) What the calculator reports
This tool converts a normal load into face pressure using P = (F × LF) / A. It also shows a design value using Pd = P × SF. In the example table, 120 kN on 0.040 m² equals 3000 kPa, and with SF 1.30 it becomes 3900 kPa.
2) Typical applications and ranges
Face pressure checks are common for jack pads, bearing blocks, base plates, formwork contact zones, and temporary supports. Pressures can span from tens of kPa for distributed loads to several thousand kPa for small contact areas. Use realistic contact dimensions, not nominal member sizes, when estimating area.
3) Unit conversions you may need
The output unit selector helps you compare specifications quickly. Useful references: 1 MPa = 1000 kPa, and 1 psi ≈ 6.895 kPa. If your project uses imperial reporting, psi and psf outputs keep reporting consistent without manual recalculation.
4) Factors and allowance checks
Load factor (LF) increases the applied load to reflect governing combinations or uncertainties. Safety factor (SF) inflates pressure for a conservative design check against an allowable limit. When an allowable is entered, the calculator reports utilization as a percentage and provides a clear pass/fail indicator.
5) Equivalent head for face support logic
The equivalent head uses h = Pd / (ρ × g) to express design pressure as a fluid column height. For water-like density (1000 kg/m³) and standard gravity, 100 kPa is roughly 10.2 m of head. This is useful when comparing pressure targets to hydraulic or slurry support assumptions.
FAQs
1) What is face pressure?
Face pressure is the normal force distributed over a contact area. It is calculated as force divided by area and reported in units like kPa, MPa, or psi.
2) When should I use mass instead of force?
Use mass when you know the weight or lifted load but not the force. The calculator converts mass to force using F = m × g, then applies factors and area.
3) What is the difference between load factor and safety factor?
Load factor scales the input load before pressure is computed. Safety factor scales the resulting pressure for a conservative design check. Keeping them separate helps match many engineering workflows.
4) How do I handle irregular contact areas?
Choose “Custom area” and enter your precomputed area in m², cm², mm², ft², or in². This is useful for segmented pads, grout footprints, or complex contact shapes.
5) Why does the tool show both pressure and design pressure?
Base pressure reflects your factored load and geometry. Design pressure includes your safety factor and is intended for comparing against allowable limits, specifications, or conservative checks.
6) What does utilization mean?
Utilization is Pd ÷ Pallow expressed as a percentage. Values below 100% indicate the design pressure is within the entered allowable limit.
7) How is equivalent head useful on site?
Equivalent head translates pressure into an intuitive fluid column height using density and gravity. It helps compare pressure targets against hydraulic assumptions, slurry support plans, or water-head discussions in reports.