Parapet Limits 2

[BadgerPE]

Is there any practical limit on the size of a parapet before it gets classified as something else? I have a project where the client is proposing a large (10-12') "parapet" (wall) around the mechanical units and to provide mounting for signage. As of now these walls are solid so no wind reduction on them. In some areas these walls are set back from the perimeter of the building. I am coming up with huge design forces and I'm trying to figure out if there are any ways to reduce the force.

We have discussed providing a roof over this to create more of a penthouse situation with louvers to provide the needed ventilation and the client is considering it. Given the footprint of this area, it would likely still meet the enclosed classification and reduce the wind load by approximately 55% at that level.

 

[SteelPE]

At some point doesn't the structure become a roof screen and not a parapet. I know in the past, when looking at a screen that is set 20' back from the edge of the roof, I have used the roof top structure requirements for wind and not the parapet requirements. I thought it gave a good balance between an increase from the MWFRS numbers but a decrease from the parapet numbers. However, I will say that I routinely design structures that are under 60' in height, so your structure may not fit into this section of ASCE 7

Edit #1: I actually think I had a similar discussion with others in regards to what constitutes a parapet. I will see if I can find the thread.

Edit #2: Here it is, I didn't read it again, but it may help you.

https://www.eng-tips.com/viewthread.cfm?qid=446522

 

[BadgerPE]

Thanks for the information and link to existing thread. I searched, but couldn't locate previously. I was only tasked with schematic level design so I assumed parapet for worst case loading--with info to the client that it could possibly be reduced in the design phase with additional research.