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[GEN/Load] Relationship between Self Weight Factor and Story Mass and Story Weight

Question

What happens to the structure's Mass (Story Mass), Weight (Story Weight), and Story Load values when a Self Weight Factor greater than 1 is input for Self Weight?

 

 

Answer

When you change the Self Weight Factor, the Story Load value changes, but the Story Mass and Story Weight values remain unaffected.
When the Self Weight Factor is changed, the Story Load value changes, but the Story Mass and Story Weight values remain unchanged. For example, consider a structure like the one shown in Image 1, where only the self-weight of the structure is considered without taking into account the floor load. If you change the Self Weight Factor to 2, as shown in Image 2, the Story Load doubles. However, as shown in Image 3 and 4, the Story Mass and Story Weight do not change.

The Self Weight function allows you to input the self-weight of elements in the model as loads, modify existing self-weight loads, or delete them. Therefore, the Story Mass and Story Weight of the structure remain unaffected.

The option to convert the structure's Self Weight into Masses is considered under 'Model > Structure Type > Conversion of Structure Self-weight into Masses,' and it is automatically calculated based on the volume and density of elements. In essence, Self Weight Factors can be considered fixed at 1.0. If you wish to double the Story Mass and Story Weight without modifying the input sections, you can achieve this by setting the Weight value to 2 for all sections under 'Model > Properties > Section Stiffness Scale Factor > Scale Factor,' as demonstrated in Image 5 and 6.

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            [Image] Analysis Model

   [Image] Story Load Table

 

   [Image] Story Mass Table   

 

   [Image] Story Weight Table

 

   [Image] Section Stiffness Scale Factor

 

   [Image] Story Weight Table when 2 is input for Weight in Section Stiffness Scale Factor

 

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