how risa-3d calculates member deflection ratios

How RISA-3D Calculates Member Deflection Ratios

After solving a model, you will see in the Member Deflections spreadsheet the following deflection ratios:

Deflection 2

These ratios are calculated using the full length of the member (L) minus any member end offsets for a member supported at both ends. For member with a cantilever end or multiple spans, please search Beam Deflections in our Help File or see the linked Tips & Tricks article below for more information.

 

The variables y and z are the local y-axis and z-axis deflections relative to the straight line between the deflected positions of the end joints. For cantilevers the deflection is relative to the original position of the member.

Deflection 1

Expressed as an equation, n = L/deflection, where n is what is tabulated in the spreadsheet above. The smaller the deflection, the larger the n value will be. If ‘NC’ is listed, that means the ‘n’ value is greater than 10000 which is a very small deflection. The minimum value that will be shown is ‘1’. For example, if the deflection criteria is L/360, check here to make sure no tabulated values are less than 360. Greater than 360 is sufficient.