Know gate forces before choosing hinges safely. Input width, height, angle, and water levels quickly. Get net thrust, pressure, and center of pressure instantly.
Enter gate geometry and water depths from the bottom edge. Use the downstream depth to get net thrust on the gate.
The hydrostatic resultant on a plane surface is: F = ρ g A hc where A is the submerged area and hc is the centroid depth below the free surface.
For an inclined plane at angle θ to the water surface, the vertical depth to the center of pressure is: hcp = hc + (IG sin²θ) / (A hc). For a rectangle, IG = b L³ / 12 using the submerged length.
Net gate thrust is the upstream resultant minus the downstream resultant. Moments are computed about the bottom edge using the vertical lever arm.
Sample inputs and typical outputs for quick validation.
| Case | b (m) | L (m) | θ (deg) | Hu (m) | Hd (m) | ρ (kg/m³) | Net force (kN) | Net moment (kN·m) |
|---|---|---|---|---|---|---|---|---|
| Canal gate | 2.0 | 3.0 | 90 | 4.0 | 1.5 | 1000 | ~66 | ~107 |
| Inclined panel | 1.5 | 2.8 | 75 | 3.2 | 0.0 | 1000 | ~65 | ~106 |
| Backwater | 2.2 | 3.5 | 90 | 5.0 | 3.8 | 1025 | ~45 | ~92 |
Hydrostatic pressure increases linearly with depth, so gate loading is not uniform. This calculator models the gate as a rectangular plane surface and integrates the pressure distribution over the submerged area. It returns a single equivalent resultant force, acting normal to the gate face, plus key pressures at the submerged top and bottom for quick sanity checks.
For each side, water depth is measured vertically from the bottom edge to the free surface. If depth exceeds the gate’s vertical projection, the panel is treated as fully submerged and the submerged height is capped at the gate size. Enter upstream and downstream levels to quantify net thrust during drawdown, backwater, or tidal reversals, and to screen worst‑case operating conditions.
Resultant force depends on the centroid depth of the submerged portion, not simply the maximum depth. The line of action passes below the centroid at the center of pressure, shifting deeper as the pressure diagram becomes more triangular. The reported moment about the bottom edge helps size hinges, trunnions, anchor bolts, and actuator torque, and it supports reaction calculations at guides, wheels, or rollers.
Engineering use should include effects beyond static hydrostatics. Consider gate self‑weight, buoyancy, uplift under seals, silt or debris loads, wave and surge increments, and ice forces where applicable. Seal and guide friction can dominate operating load for slide and lift gates. Verify plate bending, stiffener stress, weld and bolt demand, corrosion allowance, and serviceability deflection limits that protect sealing performance.
Use consistent units: meters, kilograms per cubic meter, and meters per second squared. Fresh water is typically 1000 kg/m³ and standard gravity is 9.81 m/s²; results can be divided by 1000 for kN. Record the selected angle, water levels, and any caps applied to submergence. Export inputs and outputs to preserve assumptions, support design reviews, and simplify field troubleshooting, inspection, and maintenance planning. When modeling unusual fluids, update density and consider temperature; small changes can shift thrust, moment, and hardware material decisions significantly.
Net force is the upstream resultant minus the downstream resultant. A positive value means the gate is pushed toward the downstream side, guiding hinge and actuator sizing for that operating condition.
Pressure grows with depth, so deeper areas carry more load. The integrated force therefore acts below the centroid, at the center of pressure, which depends on submerged geometry and the gate angle.
Use the angle between the gate surface and the water surface. A vertical gate is 90°. For an inclined panel, measure the slope or use geometry from drawings to compute the angle accurately.
The calculator caps submergence at the gate’s vertical projection, treating the gate as fully submerged. Additional depth above the top does not add area, but it increases pressure on the submerged surface via centroid depth.
Yes. Replace density with the correct value for the liquid. For temperature or salinity changes, update density accordingly, because force and pressure scale directly with density.
No. Results are static hydrostatic forces. Add guide and seal friction for operating load, and consider dynamic effects such as surge, wave slap, debris impact, and ice where they are credible design drivers.
Important Note: All the Calculators listed in this site are for educational purpose only and we do not guarentee the accuracy of results. Please do consult with other sources as well.