ASCE 7-10 Wind Problems
ASCE 7-10 Wind Problems
(OP)
Hi all,
I'm having some issues regarding the ASCE 7-10 classifications for structures. Specifically, what chapter I should be designing with. A little bit about the background of the project as it's a bit odd. There is some concern about adding a 4 season porch to an existing house, and according to the new state Residential Code this needs to be designed using ASCE 7. This porch is supported on posts roughly 8 ft high (there is a walkout basement, and the porch is located on the first floor), and connected to the house by knocking out the ledger board and setting the floor trusses on the existing foundation wall. What I can't seem to figure out is what to classify the porch as; not rigid (wood frame), might meet the criteria of low-rise if you take into account the overall length of the house, but not just the porch itself.
Since this is a residential building I know they won't go for an analysis to determine the frequency of just a porch. Can anyone give me a bit of guidance?
I'm having some issues regarding the ASCE 7-10 classifications for structures. Specifically, what chapter I should be designing with. A little bit about the background of the project as it's a bit odd. There is some concern about adding a 4 season porch to an existing house, and according to the new state Residential Code this needs to be designed using ASCE 7. This porch is supported on posts roughly 8 ft high (there is a walkout basement, and the porch is located on the first floor), and connected to the house by knocking out the ledger board and setting the floor trusses on the existing foundation wall. What I can't seem to figure out is what to classify the porch as; not rigid (wood frame), might meet the criteria of low-rise if you take into account the overall length of the house, but not just the porch itself.
Since this is a residential building I know they won't go for an analysis to determine the frequency of just a porch. Can anyone give me a bit of guidance?






RE: ASCE 7-10 Wind Problems
RE: ASCE 7-10 Wind Problems
Maybe this will help to get the ball rolling. If I'm adding a porch to a building, can I take the overall width of the porch plus the building to classify the structure as a low-rise building? The porch isn't self-supported.
RE: ASCE 7-10 Wind Problems
From your description, the porch is in fact self supported at the free end. At the building it is supported at a point of "infinite" rigidity (short concrete FND wall).
RE: ASCE 7-10 Wind Problems
RE: ASCE 7-10 Wind Problems
I like to think of porch roofs the same way as decks that are attached to the house. The wind loading perpendicular to the porch will put a lateral load on the porch. The roof diaphragm will act in a similar fashion to a shearwall, with one side trying to tear away from the house and the other side in compression and pushing on the house. If its not a rectangular box with a simple gable roof I just go to Part 1 of Chapter 27, the all heights method. Calculating the wind pressures is really quite simple once you've set up a spreadsheet that will handle the pesky double interpolation required with this method.
A confused student is a good student.
Nathaniel P. Wilkerson, PE
www.medeek.com
RE: ASCE 7-10 Wind Problems
It is exactly as you described it. A completely enclosed addition that is rectangular with a gable roof. Thanks everyone for your help.