October 30, 2020


Design of Back-to-Back CFS profiles now in RISAFloor


In many cases, cold-formed steel channels are built-up as back-to-back profiles in order to add strength and stability. Previously, these sections (along with face-to-face profiles) could be specified in RISAFloor, but unlike in RISA-3D could not be designed. RISAFloor v15 now includes the ability to specify, analyze and design both back-to-back (B2B) and face-to-face (F2F) cold-formed profiles made from CU or CS shapes as shown below.

CFS b2b 1

Once the back-to-back profiles are added to a RISAFloor model, they can be shown as rendered in order to verify they have been added properly.

CFS b2b 2

With the shapes added, RISAFloor can now complete a variety of code checks that are executed for back-to-back sections per the AISI. One thing to note is the required definition of the value of “a” which signifies the spacing of the connections between the back-to-back members. This value is utilized to properly calculate the slenderness (KL/r) of the member and is required to receive a code check for any back-to-back cold-formed member. This additional spacing input is listed in Beams or Columns spreadsheet:

Beams:

CFS b2b 3a

Columns:

CFS b2b 3

The Detail Report for back-to-back members shows all the controlling section properties, unbraced lengths, slenderness and connection spacing for the gravity design of the members.

CFS b2b 4

Tags: RISAFloor Cold-Formed Steel

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