Thursday, November 12, 2009

Staircase Structure 140 ft tall in OCBF?

I have a stairwell, 10 ft X 18 ft(plan dimension) x 140 ft tall structure located in SDC 'D'. The columns are braced on all sides.
This is for a tall vessel 140 ft in height. & the staircase serves as the only access to reach the vessel at different heights
for the maintenance people.  The stairwell is hardly occupied, may by 1 - 5 persons at a time per day, about 1 to 5 times
per day.
Up to a height of about 40 ft, the stairwell is laterally tied to a piperack structure(that is non building structure, similar to buildings)
located at about 10 ft from the stairwell.  The staircase serves as an access to piperack platform also at 40 ft height.
I am trying to see whether OMBF fits the staircase structure  The stair structure is not a heavily occupied structure and I think
using SMBF(many details) may be too much.  But,  IBC 2006/ASCE 7-05 assigns a height of 35 ft to OMBF under 'Building' structures.  
Can you pl. look into it & tell, under which braced system, the structure falls into(OMBF or SMBF)?  
Ravi Vasu

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