Question:
How do I define effective lengths when designing steel members in RFEM 6?
Answer:
There are two options when it comes to defining the effective lengths in RFEM 6. First, edit the member and navigate to the "Design Types" Tab. Second, create a new effective lengths definition.
Third, set whether you would like to calculate the critical moment according to an Eigenvalue method or Chapter F. from the AISC. Fourth, navigate to the "Nodal Supports and Effective Lengths" tab. Within this tab there are two different methods that can be used.
Method 1: Nodal Supports
Referencing Member No. 1 in the attached model, for this column you can see a how the effective lengths for the Start, End, and Intermediate node are defined. Check whether the node can move in the y or z axis, rotate about it's own x axis, and about it's local z axis.
Method 2: Referencing Member No. 5 in the attached model, the effective lengths can be define using "k" factors or with absolute values by checking on the option "Absolute Values."
Also, top and bottom flanges can be restrained separately by unchecking the rotation about the local x axis restraint.
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