The key to calculating the thickness of the crane outrigger pad is to consider the following three core factors:
1. Key parameters
Maximum load-bearing capacity of the outrigger (F, unit: tons or kN)
The maximum weight that each outrigger can bear.
Allowable ground pressure strength (S, unit: MPa or N/mm²)
The pressure limit determined by the ground material, such as concrete, soil, asphalt, etc.
Compressive strength of the pad material (M, unit: MPa)
Strength parameters of different materials such as UHMWPE, HDPE, steel, etc.
Contact area of the bottom of the outrigger (A, unit: m²)
The contact surface between the outrigger pad and the ground determines the pressure distribution.
2. Basic calculation method (simplified and practical)
Step 1: Calculate the actual bearing area of each outrigger
Suppose you have a 50-ton crane with 4 outriggers that evenly distribute the load:
Bearing capacity of each outrigger = 50 tons ÷ 4 = 12.5 tons
Step 2: Determine the area required for safe bearing
Formula:
Minimum required area A = outrigger load (F) / ground allowable bearing strength (S)
For example:
Assume that the soft ground bears only 0.3 MPa (= 300,000 N/m²)
12.5 tons = 125,000 N
A = 125,000 ÷ 300,000 ≈ 0.42 m²
→ The required area is approximately 650mm × 650mm plate
Step 3: Estimate the plate thickness
General empirical formula (applicable to UHMWPE material):
Thickness t ≈ (load/1000) × 2 + Safety margin
Example:
Crane tonnage Recommended UHMWPE thickness
Under 10 tons 30–40 mm
20–30 tons 40–50 mm
40–60 tons 50–60 mm
Above 80 tons 70–100 mm
Reference for compressive strength of boards (different materials)
Material Compressive strength (MPa) Characteristics
UHMW-PE 20–28 MPa Excellent impact resistance and good compression resistance
HDPE 15–25 MPa Good but slightly soft
Ordinary wood board 3–6 MPa Easy to crack
Steel plate >250 MPa Ultra-high strength, but heavy
Recommended safety design factor
To avoid risks caused by uneven ground, instantaneous impact or material aging, it is recommended to add the following when designing:
Ground factor: Increase the pressure-bearing area by 20–30%
Thickness safety margin: Thicken by 5–10mm
Corner structure design: Chamfer to prevent edge collapse