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RE: Residential Design Spreadsheet

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> -----Original Message-----
> From: Swingle, Mark [mailto:Mark.Swingle(--nospam--at)dcp.state.ma.us]
> Sent: Wednesday, July 26, 2000 6:12 AM
> To: 'seaint(--nospam--at)seaint.org'
> Cc: 'mswingle(--nospam--at)earthlink.net'
> Subject: Re: Residential Design Spreadsheet
>
>
> In addition, since Dennis' spreadsheet is for multi-story
> buildings, how
> does he account for the fact that the shear walls below the
> top story will
> not be cantilevered (single curvature), but will be fixed top
> and bottom
> (double curvature)?  The shear wall deflection formula in the
> UBC is for a
> cantilevered wall.  Is it adjusted to a fixed condition when
> there are walls
> above?

That is not correct, Mark. The wall at a given floor has three components of
deflection. First, the rotation at the lower floor level (which is zero at
the foundation) from the wall below multiplied by the wall height. Second,
the deflection of the wall itself acting as a conatilever from the wall
below. Third, the deflection of the wall below.

The wall is not fixed at the floor above unless the floor and/or beams
framing into the wall are infinitly rigid and rigidly connected to the wall
to prevent rotation.

To properly figure the distribution of forces into a wall at a given level
the rigidity is calculated relative to the foundation, not relative to the
floor below. This is how Amrhein's examples work for masonry. If the
properties change from floor to floor the modeling is more difficult. In the
masonry examples the walls conveniently do not change from floor to floor
for modeling purposes.

I am not sure what Dennis did but he probably did not account for
variability from floor to floor which would be pretty complicated.

One suggestion though, when inputting data, turn off calculations until all
the data has been entered. This might help mitigate calculation errors.

Mark


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