roof design

[ammf]

We have changed codes requiring us to design in a 110mph wind load. We must comply with sstd 10-99. This also says that we can not have anymore than a 7/12 pitch on our roofs unless we submit design calcs. I could use a little help with some design ideas and we are not going to engineered trusses.

 

[ishvaaag]

The planes in the roof themselves may act as inclined planes to resist and pass forces to the walls, ony proper joining at the boundaries (nailing to boundary elements?)will be the problem. So you need not to use trusses, you can use your usual ways with more stout members, panels and joints.

 

[ammf]

How do I show a calcuation that will prove increase of members, panels and fastners do what I say they are going to do?

 

[ishvaaag]

It depends on where you live. In Spain I think it would be "easier" since there's no mandatory code that deals specifically with the design of wood and related structures.

You or the pertinent designer may by now be proving the strength and stiffness is enough according to a method.

If the clause asking for full height corners on a width is only for the cases in which it is to be counted on for strength, you simply have to use the same methods you are presently using entirely discarding (except for passing the corner forces) the entire corner full height panel and next panel above and under window or door.

If contrarily they ask without excuse comply with such full height panel at corners there's nothing to do. You will be using the present procedure to show adequacy, yet still meet the blind width.

Then you have the alternative of framing in whatever way your building. This can produce that have even glass at the corner (which may be a civl right no code should be able to forfeit). But of course you need to prove that your structure by whatever the component systems it is made meets the required safety in front of the rveviewing party.

Since it is unlikely you are the only one having a problem with say the garages, it may be argued in front of the authority that a flexible scheme allowing for pre-qualified or qualified solutions of framing leading to the pertinent liberties and conveniences in design be met without detriment of any required safety.

Then you may use a steel or RC frame for example in the façade of the garage door and alike positions. Since the technology for these systems is well known, a reasonable reviewing party should accept the solution meet the requirements, even without a column or of course blind full height panel at corner.

Framing of course may be done as well in wood, most surely inner 45 deg knee members being useful for any potentially demanded verifications at design time. Inset of beams on columns also will work, all ending in soon to be routinized checks in a worksheet of so.

 

[ishvaaag]

You have in the collaboratory mathcad sheets freely downloadable to make calculations of wood items in classical ways (columns, beams, nails). This however won't meet you quite particularized wood framing codes, even if it enough to produce safe structures meeting both life safety and serviceability.

The straight answer to your question on how to produce the proof you are demanded to produce is "following the mandatory code". For calculations not covered there you could make use of the named sheets or other wood technology information in books or in the web.

 

[JAE]

ammf
It sounds as though you are in a situation where your building design is such that the building official is requesting engineering backup for exceeding or not-meeting a code provision. In this case, you would be wise to simply hire an engineer who can properly do this for you.