Steel structure or masonry structure supporting egress stair

[BAGW]

Hi,

If I have a steel tower or masonry shaft supporting an egress stair, do the structure needs to be designed for importance factor 1.5? I do not see anywhere in the code that explicitly defines this.

Thanks

 

[HTURKAK]

Your question implies the exterior egress stairway that are not an integral part of the building structure .

In this case, Clause 13.1.3 is applicable . The below excerpt , Copy and paste from the standard.

13.1.3 Component Importance Factor.
All components shall be assigned a component Importance Factor as indicated in this section. The component Importance Factor, Ip, shall be taken as 1.5 if any of the following conditions apply:

1. The component is required to function for life-safety
purposes after an earthquake, including fire protection
sprinkler systems and egress stairways.
.....



Use it up, wear it out;
Make it do, or do without.

NEW ENGLAND MAXIM

 

[BAGW]

Agreed for seismic forces with Ip = 1.5. What about the wind? Can this be designed with occupancy category II (I=1.0)?