News
A radial gate—also known as a Tainter gate, after Jeremiah B. Tainter who invented it in 1886—is a curved spillway gate that pivots around trunnions. Designed to allow water flow underneath, it consists of a curved steel skin plate supported by structural framing and radial arms that transfer loads to bearings located outside the water.
Superior flow control compared to flat gates at partial openings.
Cost-effective and lightweight.
Bearings remain dry—easier maintenance.
No need for overhead gate towers.
No gate slots—reduces clogging and cavitation risk.
Wider piers needed.
Concentrated loads at trunnion bearings.
Fabrication is more intricate.
Maintenance requires more complex dogging mechanisms.
Leaf Assembly: Includes curved skin plate, braces, girders, and rubber seals.
Arm Assembly: Radial arms, bracing, and hub – transfer hydrostatic load.
Trunnion Assembly: Pin, bushing, thrust washers, lubrication, and yoke.
Trunnion Support Assembly: Beam or anchor block and anchorage system.
Hoist System: Wire rope or hydraulic cylinder system to raise and lower the gate.
The curved skin plate transfers water pressure to radial arms, which pivot around trunnions. Structural design must account for hydrostatic load, self-weight, hoist forces, friction at pins, wind, debris, and ice. Second-order effects such as P-Δ and P-δ from arm deflection should also be considered in detailed modeling.
Trunnion pins are typically stainless steel and require bushings and reliable lubrication. Trunnion friction must be factored into design calculations, as it can induce significant secondary stresses and lead to arm buckling if not controlled.
Perform finite-element or limit-state analysis to validate:
Combined moment and axial loads on arms.
Potential buckling and fatigue under repeated operational cycles.
Accurate modeling of connection stiffness and imperfections for long-term reliability.
The curved shape ensures that water pressure passes through the pivot center, which reduces the torque needed to operate the gate.
You’ll need to select one of two gate styles:
Overflow-style: Allows about 1 foot of water to pass over the top in the closed position.
Breast-wall style: Sits behind a concrete wall and typically uses top rubber seals.
Rubber seals are used on the bottom, sides, and sometimes the top to minimize leakage when the gate is closed.
Skin Plate: Typically 1/4" thick steel plate welded to structural channels or I-beams.
Stiffeners: Horizontal stiffeners are sized according to the gate’s width and water head.
Radial Arms: Fabricated from rolled or built-up steel sections. Typically attached to the skin plate about one-sixth of the span in from each edge.
Trunnion Hub: Precision machining is critical. Trunnion pins must be aligned and properly supported with lubricated bushings or self-lubricating bearings.
Regular inspection and maintenance of the trunnion bearings and hoist mechanisms is critical to avoid unexpected friction or misalignment.
Common inspection points include:
Corrosion or wear in pins and bushings.
Structural fatigue in arm bracing.
Unusual vibration during operation, which could signal misalignment or arm instability.
Functionality of seals and hoist response time.
Frequent operation (cycling) is recommended to detect issues early and maintain system reliability.
| Stage | Tasks |
|---|---|
| Requirements & Layout | Determine head, opening size, overflow style, hoist type. |
| Structural & Hydraulic Analysis | Model loads, perform FE/limit-state analysis, design skin and arms. |
| Component Detailing | Specify skin thickness, arm sections, trunnion specifications. |
| Fabrication & Installation | Weld frames accurately; ensure precision in bearings and seals. |
| Commissioning & Testing | Operate at various openings; inspect for leakage, vibration, friction. |
| Maintenance Planning | Schedule lubrication, inspections, and cycling. |
A well-designed radial gate offers a balance of efficiency, strength, and durability. Engineers should pay close attention to:
Load transfer through the curved skin and arms.
Trunnion bearing design and frictional forces.
Structural detailing to prevent fatigue and buckling.
Long-term inspection and maintenance plans.
By following industry best practices in both structural and hydraulic design, radial gates can perform reliably over decades, even in the most demanding environments.
