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Wind Load force to be used in the design of isolated free standing black masonry foundation piers

Wind Load force to be used in the design of isolated free standing black masonry foundation piers

Wind Load force to be used in the design of isolated free standing black masonry foundation piers

(OP)
The National Building Code of Canada (NBC-2010) User's Guide Commentary "I" on wind pressures, Fig I7 (low rise buildings), note (4) states that "For the design of foundations, exclusive of anchorages to the frame, only 70% of the effective load is to be considered".

Question:
For free standing (i.e. little or no soil surrounding the piers) block masonry piers at about 6 feet average centres, can the 70% factor be applied i.e. reduce the wind load force applied to the top of the piers, from the wind on the cottage above, by 30%?
See attached sketch and excerpt from the User's Guide.

RE: Wind Load force to be used in the design of isolated free standing black masonry foundation piers

(OP)
Perhaps I have found the answer to my own question - the NBC definition of a "Foundation unit" is as attached ("Foundation unit means one of the structural members of the foundation of a building such as a footing, raft, or pile"). So it seems that the 70% factor for wind on foundations cannot be applied to the block piers. Do you agree?

RE: Wind Load force to be used in the design of isolated free standing black masonry foundation piers

IMO, yes.

In case of freestanding walls, design wind effects are considerably larger, than those for normal building walls (e.g., ASCE 7-05), and critical as well. As such, wind effect reduction is not likely, for these walls or their foundations.

A good structural engineer is often a blessing for others.

RE: Wind Load force to be used in the design of isolated free standing black masonry foundation piers

(OP)
Thanks PSEPK.

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