Rule of Thumb for column & wall loads?

[RJ62]

Dear Structure friends,

We often get requests for geotech investigations for buildings that are not off the drawing board. Size, placement, and loads are usually not yet decided.

Are there rules of thumb that I can use to guesstimate column and wall loads, ie 1 story wood frame: columns 50 kips, walls 3 k/ft to give the client some idea of bearing capacity and settlement?

Jefferys

 

[jike]

Since these loads can vary all of over the place, I think that it is important to get the structural engineer involved early to help estimate these loads. Often, owners, architects, project managers, etc. think that they can save money by ordering the soil borings without having sufficient load information. Realistic load information will also help the geotech determine how deep he should drill to support that load.

I think that you should explain to the person ordering the borings that it is important to have realistic load information from the structural engineer. This includes the possibility of future vertical expansion.

I have seen where some geotechs request that an information sheet be filled out before with the borings are scheduled. This sheet includes load information and building description, etc.

 

[J1D]

I doubt there is a simple chart like that, all are variables. The investigation request should come with architectural layout and structural load information. If the construction area is new, the structural engineer is somehow blind about the foundation type, depth, etc. You will then provide options and suggestions based on your findings. If the site is familiar, the new bore holes are usually for confirmation. Anyway, structural engineer should be involved in the first place. The drill is usually much deeper than the foundation or pile could reach.

 

[born2drill]

Speaking of rules of thumb, does anybody know what the guideline is for how deep a boring should be taken below the proposed subgrade of the new construction?

 

[jjeng2]

I agree with the first two posts but....It is possible and I have seen it done to use some guidelines in estimating column and footing loads. I would use a dead load of 15 psf min. for wood framing, 65 psf min for steel and conc. framing. Residential live loads of 40 psf. Office live loads of 80-100 psf. Add up your dead and live loads per use/construction and multiply by column tributary area and then multiply that by the number of floors. Im not sure if geotech guys take live load reductions or not but in an estimate I cannot see that being a major factor until you get to several stories. Exterior wall loads are based on the material. You would need an Architectural set or at a minimum guidance from thae arch. as to what they wanted to do and use the actual material weights multiplied by the square footage or height to get a plf load. Keep in mind all of this is just a guess and you will not know actual loads until you are significantly into the design process.

 

[RJ62]

Thank you everybody. I need to emphasize to our development companies that I need the architect and structural engineer involved.

Born2drill - It's been my experience that for single-story structures, borings of 15 to 20 feet are sufficient. For heavier structures, the borings need to penetrate the settlement influence zone (its deeper than the bearing influence zone) ie. 45-foot diameter oiltank, a center boring of 90 feet would be preferred.


Jefferys