Footings For A Plaza Sign - Part 9 Ontario Building Code or Part 4?

[trvvs18]

Hi to those who come across this,

Does a steel frame plaza sign require a geotechnical assessment if the footings are poured caissons such that it would fall under Part 4 of the OBC, or would this be applicable under Part 9? The sign is about 20 feet tall and 12 feet wide.

From past experience, some engineers were adamant about getting soil data for signs and others did not require it if it was for street lamps / lights (city work). Thank you.

 

[jayrod12]

Often this is dependent on the AHJ. At least in my experience. Locally, the Winnipeg plans examiners have tended to let signs go without geotechnical input. However your local authority might be stingier.

 

[STpipe]

Are you referring to using the allowable bearing pressures from Table 9.4.4.1.?

It seems to me that the code would allow you to use the values in that table, and you would need to indicate what assumed bearing pressure you used in the drawings. Whether a subsurface investigation is required would be entirely dependent on the AHJ however.

 

[trvvs18]

I guess Table 9.4.4.1. would be the go to if i can make it applicable to Part 9. Volume 2 explains an in situ test that you can perform to determine the type and condition of the soil, but who really does that? lol (i am open to doing that as it would back up my assumption i think)

If i can get away without having to do the subsurface investigation and retrieving soil data under Part 9, then i am golden. Part 4 is fine with me as well. I was just wondering if there is a code that i missed that clearly addresses this. Its understandable that it would depend on AHJ .

Thank you both by the way.

 

[STpipe]

Looking at it again, sign structures should be Part 4.

1.3.1.1.(1) The following structures are designated for the purposes of clause (d) of the definition of building in subsection 1(1) of the Act:
1.3.1.1.(1)(e) signs regulated by Section 3.15 of Division B that are not structurally supported by a building

3.15.3.1. Except as provided in this Section, all sign structures shall be designed in accordance with Part 4 (the exclusions are traffic signs, small signs, painted signs etc.)

4.2.1.1.(1) This Section applies to excavations and foundation systems for buildings

4.2.2.1.(1) A subsurface investigation, including groundwater conditions, shall be carried out, by or under the direction of a person having knowledge and experience in planning and executing such investigations to a degree appropriate for the building in its use, the ground and the surrounding site conditions. (See Appendix A.)

Reading all of these statements together makes me think the design of the foundations should be done to Part 4, which requires a subsurface investigation.

However, the Appendix does give you an out where it states "Where acceptable information on subsurface conditions already exists, the investigation may not require further physical subsurface exploration or testing". So if the sign is near a building where the AHJ would have those records, then you could get around that.

 

[EngDM]

Reading all of these statements together makes me think the design of the foundations should be done to Part 4, which requires a subsurface investigation.

However, the Appendix does give you an out where it states "Where acceptable information on subsurface conditions already exists, the investigation may not require further physical subsurface exploration or testing". So if the sign is near a building where the AHJ would have those records, then you could get around that.

I agree with the statement above, this is how we have typically done it. However, depending on AHJ we have also done it assuming values that are deemed conservative for our area (I think we use 75psf bearing) and note that on the drawings.

 

[jayrod12]

(I think we use 75psf bearing)

I assume you mean in the lateral direction? 75 PSF is lower than quicksand. There's a larger than 75 PSF bearing load under my shoes.

 

[trvvs18]

[Reading all of these statements together makes me think the design of the foundations should be done to Part 4, which requires a subsurface investigation.

However, the Appendix does give you an out where it states "Where acceptable information on subsurface conditions already exists, the investigation may not require further physical subsurface exploration or testing". So if the sign is near a building where the AHJ would have those records, then you could get around that.]

Thank you all for the input and assistance. I think the above has answered my question and provides direction.

[There's a larger than 75 PSF bearing load under my shoes.]
This made me laugh. Thank you.