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Re: Cracks in Blocks in Fire Tower

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Gary,

        Assuming the eye bolts stick out of the top of the parapet a
possible fix might include a cap channel on top of the wall.  8" concrete
blocks have an actual dimension of 8.5 to 8.625 depending on
manufacturer, therefore, putting a C8x11.5 (C200x17) on top (flanges
down) should require only a moderate amount of block grinding to get a
secure fit.  The channel could be continuous (best) or in increments of a
foot or two depending on spacing of the eye bolts.

        If the eye bolts are on the face of the parapet you might
consider a face plate (or a channel with he flanges embedded in the grout
lines.  Use a through bolt with a washer or back plate on the back of the
parapet.

        Another thing: fall arrest devices in the construction industry
commonly require extremely large safety factors.  I don't know the code
requirement for your application for 2004; but you may want to review the
5/8" eye bolts and possibly replace them with something larger.  You
should design this thing for at least 5,000 pound loading.

Regards,

H. Daryl Richardson

Gary Hodgson & Associates wrote:

> Approximately 10 years ago, I designed a 4 storey fire training tower
> for the City of Niagara Falls.  The construction was 8" reinforced
> block with a 42" high parapet.  In the parapet I embedded 5/8" eye
> bolts to be used for anchoring rapelling ropes for climbing down the
> tower.  Almost every one of theses bolts has radial cracks around the
> bolt shank circulating out 2" to 4".  The fire department cut off the
> eye bolts to stop their use.  There are still U bolts in the roof
> slab so they can still train.  However, they want to have the eye
> bolts or an equivalent re-installed in order to have different means
> of anchoring for training.  I guess not all buildings are the same.
>
> Does anyone have any suggestions as to the cause of the cracks in the
> block or alternative means of anchorage to the parapet wall?  Photos
> are available if anybody's interested.
>
> thanks,
> Gary Hodgson
> Niagara Falls, ON
>
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