UNL PARAMETER BS5950

UNL is the unsupported length of member used in lateral torsional buckling moment capacity calculation. If you do not assign UNL the program will consider the node to node length as default. But, if you assign UNL, it will take the user defined value. In this case for example member 33, with UNL the LTB length is considered as 1.8m and corresponding LTB moment capacity is 21.27 kN-m.

But when you assign UNL as 3.35m, LTB length is reported as 3.35m and corresponding LTB moment capacity is reduced to 16.62 kN-m.

Hope this clarifies.

UNL is the unsupported length of member used in lateral torsional buckling moment capacity calculation. If you do not assign UNL the program will consider the node to node length as default. But, if you assign UNL, it will take the user defined value. In this case for example member 33, with UNL the LTB length is considered as 1.8m and corresponding LTB moment capacity is 21.27 kN-m.

But when you assign UNL as 3.35m, LTB length is reported as 3.35m and corresponding LTB moment capacity is reduced to 16.62 kN-m.

Hope this clarifies.

Thanks for the reply sir. For example member 33, when there are lateral restrain, do i need to assign length of the restrain as 1.8m or the length of the full member 3.35m?