How does Tekla Structures calculate weight?

What is the weight, gross weight and net weight of a steel part?

Tekla Structures has three main weight measures: weight, gross weight, and net weight. You can use the Inquire command, or create a report to find out these values.

The three types of weights are calculated differently depending on what type of profile defines the modeled part. In Tekla Structures, there are mainly two types of profiles:

(a) Standard profiles, which can be obtained pre-manufactured, have properties indicated in a catalog and vary between environments
(b) Parametric profiles, which have a predefined, hard-coded shape, with one or more parameters to define the size of the profile.

Often, especially in parametric profiles, to understand weight, gross weight and net weight, we need to know how Tekla Structures defines volume, gross volume and net volume:

Volume: Is the object volume, takes cuts and holes into account.
Gross Volume: Is the object volume, does not take cuts and holes into account.
Net Volume: Is the object volume, takes cuts and holes into account. In parametric profiles, this is the same as volume.

Standard profiles:

These are usually steel sections, such as I-beams, rectangular and circular hollow sections, for example. In Tekla Structures, these are marked with a blue cube symbol in the profile catalog.

Predominantly, the weights are ruled by the cross sectional area specified in the profile catalog (Analysis tab), except net weight.

• Volume : Profile cross section area x Length

                         = 5550mm2 x 1000mm = 5550000mm3

• Volume Gross : Profile cross section area x Length

                         = 5550mm2 x 1000mm = 5550000mm3

• Volume Net : Modeled volume

                         = 5600000mm3

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Weights in standard profiles are determined by multiplying the respective volumes with the material density:

Weight = Volume x density of material
             = 5550000mm3 x 0.00000785 kg/mm3 = 43.56 kg

Gross Weight: For standard profiles, this is the same as weight.

Net Weight: Is the actual weight of the part shown in the model, defined by the formula:
           = Modeled volume (net volume) x density of material
           = 5600000mm3 x 0.00000785kg/mm3 = 43.96 kg

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Since net weight is governed by the modeled part volume, it can be affected significantly if XS_SOLID_USE_HIGHER_ACCURACY is set to TRUE in the options.ini file in model folder. When set to TRUE, the root radiuses and roundings in the profile are taken into account. Net weight becomes more accurate.

Parametric profiles:

For comparison purposes, an RHS parametric profile is used to resemble the RHS200*100*10 beam with 1m length.

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Since parametric profiles do not have a proprietary cross sectional area, it is shown as zero in the report. Hence, all volumes are calculated using the modeled volume:

Volume  = Volume Gross = Volume Net
              = 5600000mm3

Weight   = Gross Weight = Net Weight
              = 5600000mm3 x 0.00000785 kg/mm3 = 43.96kg

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