4. Padeye Stress Calculation:
5. a) Tension Stress:

The tensile stress (σt​) on the padeye plate is calculated using: σt=P/ t×W

 Where:

• P = Design load
• t = Padeye thickness
• W= Width of the padeye

Ensure that the tensile stress is less than the yield strength of the material (fy​).

1. b) Bearing Stress:

The bearing stress (σb​) around the hole (where the shackle pin is placed) is: σb=P\dh​×tP​ Where:

• P          = Load applied
• dh​        = Hole diameter
• t           = Thickness of the padeye plate

The bearing stress should be checked against the allowable bearing stress for the material.

1. c) Shear Stress:

The shear stress (τ) on the padeye is calculated as: τ=P/ 2×t×W

Where:

• P          = Applied load
• t           = Thickness of the padeye plate
• W        = Width of the padeye

Shear stress should be less than the allowable shear strength of the material, typically 0.6fy

1. d) Bending Stress:

For a padeye subjected to bending due to out-of-plane loading or eccentric loading, the bending stress (σb ​) can be calculated using: σb=M / S

Where:

• M        = Bending moment
• S          = Section modulus of the padeye cross-section

Ensure that the bending stress does not exceed the allowable stress of the material.

5. Check Against Failure Modes:

• Tensile failure: Ensure that the tensile stress does not exceed the allowable tensile stress of the material.
• Bearing failure: Ensure that the bearing stress at the hole does not exceed the material’s bearing capacity.
• Shear failure: Check that the padeye can resist shear forces.
• Bending failure: If there is eccentric loading, check that the bending stresses are within safe limits.
• Tear-out failure: Ensure the distance from the hole to the edge of the plate is sufficient to prevent tear-out.

6. Safety Factor:

Apply a safety factor to the design to account for uncertainties in load estimation, material strength, and fabrication quality. A common safety factor for padeyes is 1.5 to 3, depending on the application.

7. Weld Strength (if applicable):

If the padeye is welded to a structure, ensure that the welds are designed to handle the applied loads. Check both the throat size and the length of the weld.

Conclusion:

The design of a padeye requires careful consideration of material strength, geometry, and load application. The stresses (tensile, shear, and bearing) must be checked, and the design must meet the required safety factors. Accurate calculation ensures the padeye can handle the lifting operation without failure.

Example Calculation:

• Load (P):                                            =          50 kN
• Material: Steel with yield strength fy=         250 Mpa
• Padeye thickness (t):                         =          20 mm
• Hole diameter (d_h):                         =          25 mm
• Padeye width (W):                             =          100 mm

1. Tension Stress:

σt = 50,000 / 20×100 =25 MPa

(Tensile stress is less than fy​).

1. Bearing Stress:

σb =50,000 / 25×20 =100 MPa

(Check against allowable bearing stress).

1. Shear Stress:

τ = 50,000 / 2×20×100=12.5 MPa

(Shear stress is within limits).

By following these steps and performing necessary calculations, the Padeye design will ensure safe and efficient lifting operations