In some cases, local codes mandate certain material combinations. A municipality may legislate that all new structures use brick or stone veneers, for example. The builder would use special ties to connect the CFS framing with the brick or stone.
Often, multi-material systems feature CFS framing for its deflection characteristics. To create an effective lateral force resisting system, concrete or masonry will be used at elevator shafts and stairwells. But, CFS stud shear walls can be added to share some lateral load.
Of course, economics can also drive the union of CFS with other materials. Architects and engineers may choose certain combinations of materials based on a project budget. For example, a structure could feature load-bearing CFS-framed walls connected to a wood-framed roof.
How to transfer loads between materials
The key to getting these connections between CFS and other materials right involves understanding the specifications for each material.
You’ll want to consult:
Take AISI S240-15, Section B1.5.6, entitled “Connection to Other Materials,” for example. It states:
Bolts, nails, anchor bolts or other fasteners used to connect cold-formed steel framing to wood, masonry, concrete or other steel components shall be designed and installed in accordance with the applicable building code or the approved construction documents.
“We’re looking to the building code to guide us in the design of connecting CFS with other materials,” LaBoube said.
AISI S100-16, Section J7.1.1, entitled “Bearing,” equates material connection with load transfer. It states:
Provisions shall be made to transfer bearing forces from steel components covered by this Specification to adjacent structural components made of other materials.
The process of connecting CFS with other materials is “nothing unique or magical,” LaBoube said. “It’s a matter of recognizing that we need a load path. The load path has to transfer from the cold-formed steel, through the connector, and into the other material.”
This is where you’ll need the strength equations for the other material — the concrete specification, the masonry specification, the wood specification, etc. AISI S100-16, page 151, says:
When a cold-formed steel structural member is connected to other materials, such as hot-rolled steel, aluminum, concrete, masonry or wood, the connection strength should be the smallest of the strength of the fastener, the strength of the fastener attachment to the cold-formed steel structural member, or the strength of the fastener attachment to the other material.
According to LaBoube, interfacing CFS with another material requires “looking at the strength of the connection in the CFS as well as the connection strength required by the other material.”
This information will you started in transferring loads in multi-material systems, but if you have additional questions about making proper connections between CFS and other materials on your next CFS-framed project, request complimentary project assistance from our team of experts.