Shear Wall Without Shear

[CURVEB]

(This is strictly a theoretical topic. I would never design a shear wall assuming it takes no in-plane loading.)

My question is this: is it theoretically possible, by analysis, that you could have a shear wall supporting a rigid diaphragm and determine that the wall takes a shear force of zero? In other words, could the torsional shear be equal and opposite the direct shear, causing a net force of 0?

Has anyone ever run into this issue when reviewing analysis results from RISA, RAM, Enercalc, Etc? I like that enercalc includes the option to neglect torsional forces when they reduce the shear. It would be nice if this work possible to incorporate into other analysis packages.

 

[KootK]

My question is this: is it theoretically possible, by analysis, that you could have a shear wall supporting a rigid diaphragm and determine that the wall takes a shear force of zero? In other words, could the torsional shear be equal and opposite the direct shear, causing a net force of 0?

Yup. Near zero and sometimes opposite direction. Darn near anything is possible with a rigid diaphragm. If your walls are yielding under seismic demand, and your model considers the wall to be infinitely elastic, that will sometimes change the situation a fair bit.

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.

 

[PicoStruc]

Just saying but wind and seismic loads are reversal loading.

The accidental torsion may happen on both side of the center of mass, causing reversal of torsion component !

So, in my opinion, it is not possible to have a monolotic wall taking no shear at all in a design point of view.

EDIT : In a single elastic analysis though, you may get a zero shear but it is probably not the combination of load causing maximum shear in the wall. See explanation above.

 

[CURVEB]

Agreed.

 

[DETstru]

Definitely possible. I've had a number of cases where I had near-zero shear in a shear wall with funky floor plates. Usually it's no big deal because you have to run the combinations with the eccentricity on the other side of the CG as well.

Just for good measure I often run another analysis without the eccentricity just to see how things are otherwise behaving.