This article explains the process for calculating how many blocks are required in order to place a container on top of them.
INTRODUCTION
Properly supporting a container on blocks is crucial for safety. This article provides a step-by-step guide to determine the necessary number of blocks and their minimum required strength (MPA) when using Interbloc products for container support.
FORMULA AND CALCULATIONS
- Weight per Block:
- Divide the total weight of the container (in kilograms) by the number of blocks used for support.
- Kilonewton Metres:
- Multiply the weight per block (in kilograms) by 9.80665 to convert it to kilonewton metres (kNm).
- Bearing Area:
- Calculate the bearing area of the block in square millimetres (mm²) by multiplying its length and width (in millimetres). For standard Interbloc blocks, the dimensions are 180mm x 160mm, resulting in a bearing area of 28,800 mm².
- Applied Pressure:
- Divide the weight per block (in kNm) by the bearing area (in mm²) to determine the applied pressure in Newtons per square millimeter (N/mm²). Note that 1 N/mm² is equivalent to 1 MPa (Megapascal).
REAL WORLD EXAMPLES
Let’s consider a 5-tonne container supported by four concrete blocks:
- Weight per block: 5000 kg / 4 = 1250 kg
- Kilonewton metres: 1250 kg * 9.80665 = 12.258 kNm
- Applied pressure: 12.258 kNm / 28,800 mm² = 0.0004256 kNm/mm² = 0.4256 N/mm² = 0.4256 MPa
INTERBLOC PREMIUM BLOCK STRENGTH
Interbloc premium blocks have a minimum MPa of 20. For calculating bearing stress, a safety factor of 0.15 is applied, resulting in a minimum working MPa of 3. In our example, the calculated applied pressure of 0.4256 MPa is well below this limit, providing a safety factor of approximately 7.
IMPORTANT CONSIDERATIONS
- Bearing Area: The bearing area is determined by the size of the locking knobs on the container’s corners, which typically measure 180mm x 160mm.
- Additional Safety Measures: Secure the container against lateral movement due to wind or earthquakes. Consider using shear keys to prevent accidental block slippage (especially when stacking blocks) and assess the ground’s bearing capacity.
- Even Distribution: Ensure the container’s weight is evenly distributed across all supporting blocks.