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# Re: Roof height for A-Frame

• To: seaint(--nospam--at)seaint.org
• Subject: Re: Roof height for A-Frame
• From: "William Haynes" <gtg740p(--nospam--at)gmail.com>
• Date: Tue, 11 Nov 2008 21:08:42 -0500

```So what roof level should be used when calculating the period of the
building for wind or seismic loads? I am trying to think about it
behaving dynamically with the modes of freedom it would have along
either axis. Could the gable roof building have different periods in
each direction?

On Tue, Nov 11, 2008 at 1:58 PM, David Topete <d.topete73(--nospam--at)gmail.com> wrote:
> Okay, that's what I was thinking as well, although it doesn't seem to
> jive...
> I am looking at a URM (unreinforced masonry, err... brick) building.  The
> pony wall along the long edges which the rafters bear is the URM wall,
> extending only 4 courses above the second floor sheathing, about 12".  The
> gable end walls are brick that extend to the roof ridge.  Seismic will
> govern either force direction due to its mass.
> any other thoughts given some more detailed information?  Thanks again for
> everyone's input.
>
> On Tue, Nov 11, 2008 at 9:26 AM, William Haynes <gtg740p(--nospam--at)gmail.com> wrote:
>>
>> My first impression is the same as what Gordon states.
>>
>> Will H
>>
>> On Tue, Nov 11, 2008 at 10:57 AM, Gordon Goodell
>> <GordonGoodell(--nospam--at)harmonydesigninc.com> wrote:
>> > David,
>> >
>> >
>> >
>> > Are you taking roof height for wind or seismic?  For wind it would be
>> > the
>> > average height, ½ way between eave and ridge.  For seismic, roof height
>> > is
>> > where the diaphragm attaches, so at the plate, top of your pony walls.
>> >  And
>> > it's a stretch to call this a single storey...You've got a roof
>> > diaphragm
>> > and an upper floor diaphragm, even though for equivalent lateral force
>> > procedure your h values for each level are only separated by 18".
>> >
>> >
>> >
>> >
>> >
>> > regards,
>> >
>> > Gordon Goodell
>> >
>> >
>> >
>> >
>> >
>> > From: David Topete [mailto:d.topete73(--nospam--at)gmail.com]
>> > Sent: Monday, November 10, 2008 6:55 PM
>> > To: SEAINT
>> > Subject: Roof height for A-Frame
>> >
>> >
>> >
>> > Where would the "roof height" be defined for a "single-story" structure
>> > with
>> > enough volume below the roof (12:12 pitch) that creates a second floor?
>> >  The
>> > gable ends extend to the roof ridge, while the rafters bear on a pony
>> > wall
>> > +18" above the second floor.  The second floor is 11'-0" above the
>> > ground
>> > floor.  Any thoughts would be much appreciated.  TIA.
>> >
>> > --
>> > David Topete, SE
>> >
>> > ExchangeDefender Message Security: Check Authenticity
>> >
>
>
>
> --
> David Topete, SE
>
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