I think that sometimes steelwork is overdesigned, but more often than not, people simply don't realise what actually goes into designing steelwork.
It's not as simple as load on a given span. An unrestrained beam carrying a timber floor might need to be larger than a restrained beam carrying a concrete floor.
It's not as simple as having a beam that doesn't deflect much. Some beams might have next to no deflection but exceed their moment capacity.
Connections are another issue. It may be more economical to install a larger beam than to design and fabricate a complicated connection so that a smaller beam will work.
Or what about the loads the beam is carrying. A 203x102 may well have the capacity to carry a 330 thick wall by itself, but how are you going to sit a 13" wall on a 4" beam?
Safety factors take into account the fact that building is not an exact science. How often does the final building measure up exactly to what's on the drawings? Quality of fabrication is variable too.
I don't think anyone should mind paying slightly more for a slightly larger steelwork section for the peace of mind that it provides. The SE and fabrication costs are usually a fraction of the overall job cost anyway.
It's not as simple as load on a given span. An unrestrained beam carrying a timber floor might need to be larger than a restrained beam carrying a concrete floor.
It's not as simple as having a beam that doesn't deflect much. Some beams might have next to no deflection but exceed their moment capacity.
Connections are another issue. It may be more economical to install a larger beam than to design and fabricate a complicated connection so that a smaller beam will work.
Or what about the loads the beam is carrying. A 203x102 may well have the capacity to carry a 330 thick wall by itself, but how are you going to sit a 13" wall on a 4" beam?
Safety factors take into account the fact that building is not an exact science. How often does the final building measure up exactly to what's on the drawings? Quality of fabrication is variable too.
I don't think anyone should mind paying slightly more for a slightly larger steelwork section for the peace of mind that it provides. The SE and fabrication costs are usually a fraction of the overall job cost anyway.
