Retaining Wall Tow Acting as Column Footing

[dbest69er]

Hi,

I was wondering if it's common to use retaining wall toe to double as a footing for a column similar to the detail shown attached(except the wall will be in-situ concrete and not precast).

What checks would I have to perform to ensure it works. The retaining wall itself is adequate to take the retained soil but now, the concrete pedestal will be taking the soil pressure as well as the column reactions?

I'm inclined to design the pedestal as a concrete column. Does anyone have any advice or other input on anything I'm missing?

Thanks,

Keith

 

[KootK]

We're talking about a retaining wall laterally supported at the top rather than a cantilevered wall, right? I'll assume so for now.

1) I wouldn't say that it's common but it's certainly been done before.

2) I suspect that most designers would design the retaining wall as though the pedestal were absent and the pedestal and it's "footing" as though the retaining wall were absent (no soil pressure on the pedestal. This probably would not be conservative in all respects.

3) The pedestal would be the stiffer thing. Looking at it rigorously would be quite involved:

- will the wall one-way shear its way off of the pedestal? You'd need hanger stirrups like with an upturned beam.

- will the wall need dirt side horizontal bars to deal with the flexure near the pier? A certain width of wall will deliver load to the pier rather than resisting it as a retaining wall.

- the pier potentially failing in moment isn't a big deal so long as the wall can resist the soil alone.

- The pier potentially failing in shear is a bit of a bigger deal. Although, one could argue that even a shear failure in the pier wouldn't necessarily compromise its axial capacity.

- Whatever load is delivered to the pedestal, that will result in base moments at the pedestal to footing connection if that is considered a point of fixity. As such, you'd need a punching shear check there for axial + moment.

- The footing would need to be designed as as eccentrically loaded.



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.