Re-cladding of building using cold formed steel sub-frame

The results of research into the effective use of steel sub-frames as part of re-cladding and overcladding systems for high- and low-rise buildings are presented. An objective of the research was to study the interaction between new cladding systems and their attachment to existing buildings, and to develop appropriate guidance on the use of steel in this application. Existing over/re-cladding systems using aluminium extrusions require many fixings to attach the support rails to the underlying concrete structure. Cold-formed steel (CFS) sub-frames exist whose greater stiffness helps to reduce the number offixings. Such a sub-frame, with fewer but stronger fixings yet with the redundancy to provide alternative load paths once one fixing fails, has been the subject of an experimental study, with the results correlated with individual fixing tests. The sub-frame systems were also modelled numerically and a design model was developed. The numerical work has been used to interpret the sub-frame tests and to establish the criteria for the overall factor of safety for such systems. The analysis evaluates the effects of the sub-frame flexibility and anchor stiffness on the behaviour of the cladding support system.