I want to know where cold formed steel framing is used, is every steel frame we see in a construction sites like houses, building and bridges cold formed steel frames? or hot formed steel framing?I also read that cold formed steel framing is used for floors, is the steel frame beneath the floor's concrete cover?Thank u very much!!
Abeer: I'm a civil/structural engineer. Cold-formed (or rolled) steel framing is typically limited to facades, studs in lightly-loaded bearing walls and non-load bearing wall studs. Hot-rolled steel members are typically used to frame steel buildings and bridges. See the article below on cold-formed steel framing.
It will vary from location to location. A possible way of telling is how the material is joined. If the material is riveted together it is likely cold rolled. If the material is welded then its probably normalized steel (possibly annealed but less likely). Cold rolling increases the yield strength of the material so less of it is needed. However, it also make the material more brittle. Welding creates defects in the region surrounding the weld and these are more likely to grow and cause failure in a cold rolled steel than a normalised or annealed steels. In addition the heat from the welding will change the microstructure that was deliberately introduced by the cold rolling process resulting in a localised drop in yield strength. Normalised and annealed steels are more ductile and tougher than Cold rolled steel but they have a lower yield strength. Because they are tough and ductile they are less sensitive to crakcs and defects so welding won't lead to as big a reduction in strength. Another possible consideration is the environment they are used in. Steels exhibit a transition temperature (actually more like a range) where they go from behaving like a ductile material to a brittle material. A well known example of what this can cause are the Liberty ships in WW2 (Supply vessels from the US to the UK). These were made by welding together sheets of cold rolled steel to form one continuous Hull. Unfortuantely the transiton temperature of the steel taht was sued was around 4 degrees while the Baltic Ocean is about 0 degrees. As a result small cracks would grow and then when the reached a critical size they would tear through the ship at the speed of sound in the metal (1500m/s) and these massive cargo ships would literally snap like twigs. So, if the steel is being used somewhere really cold its unlikely to be Cold rolled too.
