5.2.14.12   Slabs - line loads

Variation in loading and securing as a function of the dimensions and masses of the slabs
 
 
Transport options
 
 
In order better to clarify any differences in packing and securing, the following examples relate to the two slabs shown, which are of the following dimensions.
 
 
Upper slab:
Length 4,270 mm
Width 1,400 mm
Height 510 mm

 
Its mass is 23,160 kg (23.160 metric tons). An exact conversion reveals a weight-force or normal force of 227,199.6 newtons or 22,712 daN or 22.712 kN (23,160 kg x 9.81 m/s² = 227,199.6 newtons).
 
The line load of the slab can be determined by dividing its mass or weight by its length, so producing the following Figures:
 
 
Mass/weight Length of slab Line load
23,160 kg 4.27 m 5,423.888 kg/m
227.1996 kN 4.27 m 53.208 kN/m

 
Lower slab:
 
Length 3,100 mm
Width 1,400 mm
Height 710 mm

 
Its mass is 23,463 kg or 23.463 metric tons. An exact conversion reveals a weight-force or normal force of 230,172 newtons or 23,017.2 daN or 230.712 kN.
 
The line load of the slab can be determined by dividing its mass or weight by its length, so producing the following Figures:
 
 
Mass/weight Length of slab Line load
23,463 kg 3.10 m 7,568.710 kg/m
230.17203 kN 3.10 m 74.249 kN/m

 
In box containers the floor is constructed from the transverse bottom cross members with textured coated board or plywood sheet or plank flooring. Floors are intended to carry uniformly distributed loads.
 
The admissible line load of 20' containers is determined by dividing the admissible payload by the value obtained after subtracting 2 m from the container's length. A completely accurate calculation would require this value to be deducted from the container's loading length.
In rough terms, the admissible line load for 20' containers can be calculated by dividing payload by 4 m (approx. container length of 6 m minus 2 m).
 
Since older types of standard containers with a payload of approx. 18,000 kg have admissible line loads of only 4,500 kg/m, such containers cannot be used. Even special measures to distribute the pressure are of no assistance here as the mass of the cargo exceeds the container's payload.
 
However, any container having a payload or line load which matches or even exceeds the mass of the slab or the line load it applies may be considered.
 
The minimum container payload required for individual heavy cargoes can be calculated by multiplying the line load applied by the cargo by the reference size used for calculating the line load for the particular container length, i.e. 4 m for 20' containers:
 
The minimum container payload required to accommodate the upper of the above-stated stainless steel slabs may accordingly be calculated as follows:
 
 
Line load applied by slab Reference length of container Minimum required container payload
5,423.888 kg/m 4.00 m 21,695.552 kg
53.208 kN/m 4.00 m 212.832 kN

 
The calculation shows that no older type ISO containers can be considered, only newer types. Purely theoretically, older type 40' containers could be used to transport the slab as they have a payload of approx. 27 metric tons. However, since the admissible line loads of these containers are only approx. 3 metric tons/m, considerable quantities of material would be required for propping/load distribution. It is accordingly uneconomic to use 40' containers.
 
The minimum container payload required to accommodate the lower of the above-stated stainless steel slabs may accordingly be calculated as follows:
 
Line load applied by slab Reference length of container Minimum required container payload
7,568.710 kg/m 4.00 m 30,274.840 kg
74.249 kN/m 4.00 m 296.996 kN

 
The calculation shows that, at the time of loading, neither older type ISO containers nor newer type 20' containers could be considered for this slab, as there was at that time no commercially available 20' box container with a payload of more than 30 metric tons.
 
Purely theoretically, newer type 40' containers could have been used to transport the slab as some would have the necessary payload. However, since the admissible line loads of these containers are only approx. 3.3 to 3.5 metric tons/m, even greater quantities of material would be required for propping or for load distribution than for the "upper slab". For these reasons, box containers cannot be used to carry the "lower slab".
 
 

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