Building a steel structure is one thing - being able to move around from level to level and between floors is another.
There are 3 scenarios to consider here, each having their own set of governing regulations:
Public Access - Providing access for the general public - this could be in commercial or residential buildings extending to public buildings and facilities such as museums, theaters, stadiums etc... Access facilities for these areas, where public health and safety is the main consideration are usually governed by legislation incorporated into regional codes and building regulations.
For more about this see Introduction to Stairways
Emergency Access - This covers emergency escape routes such as fire escapes. Though it is a public access area different regulations may apply, particularly with regards to handrails and landings - often, there must be space provision for negotiating stretchers and 'Carry Chairs' for the injured and disabled.
Maintenance Access - Here, the regulations are slightly more tolerant provided the access is defined as a maintenance space for authorized personnel. In some cases it may require the use pf personal safety equipment.