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Re: Kneebraced Post Design

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Chris, I was looking at your formulas, thinking about lookup tables, and just happened to notice an error in cell B15 - the value for the 0.5 inch lag screw is way out of line.

On Fri, May 9, 2008 at 6:42 PM, Chris Slater <chris(--nospam--at)jdwylieengineering.com> wrote:
Here's a better link to the spread sheet.  I think that makes clear
what we're doing, since it has a diagram in it.

http://examplecalcs.com/kneebrace.xls

On Fri, May 9, 2008 at 3:32 PM, Michel Blangy <mblangy(--nospam--at)satco-inc.com> wrote:
> Chris,
>
> This kind of thing is right up my alley. I remember doing a raised deck for
> a frat house in Boulder, CO about 10 years ago that had a hot tub on it!
> That one used knee braces and was very stout, however, I have on occasion a
> need for the type you describe. Is there anyway you could provide more
> detail of your connection?
>
> Michel Blangy, P.E.
>
>
>
>
>> -----Original Message-----
>> From: chris.slater(--nospam--at)gmail.com [mailto:chris.slater(--nospam--at)gmail.com]On Behalf Of
>> Chris Slater
>> Sent: Friday, May 09, 2008 2:47 PM
>> To: seaint(--nospam--at)seaint.org
>> Subject: Kneebraced Post Design
>>
>>
>> Tried sending this earlier, and it never made it.  I'm assuming the
>> list doesn't like attachments.  Instead, I've included a link to the
>> file on my web server.
>>
>> --
>>
>> A lot of our firm's work is residential, and of that, a moderate
>> percentage is small additions and remodels.
>>
>> One thing that we see very often (and more frequently as jurisdictions
>> start getting tougher about requirements) is small covered patio
>> additions.
>>
>> Engineering the lateral support for these is tricky.  The favored
>> solution for owners and contractors is to kneebrace the support posts.
>> We've done this in the past, and made it work for small patios, using
>> NDS combined lateral and pullout values for Lag Screws, and an R value
>> of 4.5 (UBC).
>>
>> In the new code, we have to use R=1.5, which means that even for a
>> small patio, the seismic load is fairly high, and it is very difficult
>> to make this work.  However, in an effort to not have to specify steel
>> columms for every little patio we engineer, we've tried to look at
>> other options, such as 1/4" steel side plates with either lag screws
>> or through bolts.
>>
>> I developed a spreadsheet, using the NDS equations, that gives options
>> based on what we put into it.  I've attached the spreadsheet to this
>> e-mail (actually, it's here:
>> examplecalcs.com/Kneebraced%20Post%20Design.xls)
>> and would appreciate it if any of you had time to review it and
>> offer feedback.  If you find it useful, please feel free to keep a
>> copy.
>>
>> So the request for feedback is my first request.  But I also am
>> interested in what others are doing with regard to small patios and
>> knee braced posts.  I know that this type of thing falls way below the
>> radar of many on this list, but it is something we run into very often
>> in our practice.
>>
>> Thanks,
>>
>> Chris Slater
>>
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