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Grade beams supporting concrete shear walls 2

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Okiryu

Civil/Environmental
Sep 13, 2013
1,094
Hi, a question from a geotechnical guy: I am just looking at some structural plans, and noted some 300 mm thick shear walls with loads ranging between 40 kN/m to 50 kN/m. These walls are supported in continuous footings. I was thinking that since loads are not too high, it may be possible to support these walls in grade beams? or shear walls should be supported always by footings? Any special reasons on doing one or the other? Thanks in advance for your input.
 
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and treat the wall load as a point load on the grade beam due to the relative stiffness of the wall:beam. I've done numerous 20 storey buildings using that approach.

Dik
 
@Kootk, thanks for taking the time to explain this. Right now, the design shows continuous footings supporting the shear walls. The width of the footings is small (0.5m), footings thicknesses are 0.3m. Not sure how the EOR is modelling the walls-foundation, but if plastic hinges occur and therefore large punching shear will develop, appears that the current footings are too small?

@dik, that is interesting, so you just assume a large point load acting at the middle of the span of the grade beam?
 
Okiryu said:
plastic hinges occur and therefore large punching shear will develop, appears that the current footings are too small?

Truly, I don't know enough to speculate meaningfully. It could be a rocking foundation, a squat wall system, a low seismic foundation, or a foundation beneath a deep basement. I wouldn't invest any time in this until you get clarification from the EOR regarding their intent.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.
 
Thanks Kootk, will talk with the EOR next week and see how it goes.
 
Okiryu:
Not in the middle of the span, but at the ends of the shear wall... As I noted, any dowels from the grade beam to the shear wall are in tension due to the relative stiffness of the wall to the beam. The beam is designed, however, for any construction loading prior to the concrete setting... generally not significant.

Dik
 
dik, thanks for the clarification. Your approach follows Kootk comments about shear forces at the end of the walls. Good to know it.
 
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