overhang values

[Robert216]

For a porch roof (all is open), is it appropriate to apply overhang values for design of the rafters/ trusses and connections? If not, what would be appropriate? I believe that we would need to account for positive pressure on the underside of the roof (or porch ceiling) and negative pressure on the top side of the roof deck. I have always treated this as an overhang condition, but would like to know how others treated this condition.

Thanks,

Rob

 

[MiketheEngineer]

You need to check for both --- say a downward live and dead load and/or an upward wind live load. Also - you need to be carefull at the edges of the buildings for higher loads. Check out IBC2006 or ASCE

 

[Robert216]

I understand that I need to check for all of these. My real question is this: Are the components and cladding "overhang" (simplified method-the table) values appropriate? These are very high and these are what I have always used when designing for uplift. Should I use an analytical procedure and treat this as an open structure? I am just curious as to what other engineers use.

Thanks, Rob

 

[Ron]

I would use analytical procedure as an open structure. I routinely use that for aluminum canopy structures (similar to your application, different materials).

 

[Robert216]

Thanks Ron