Concrete Wall Twisting Moment

[ChiEngr]

Hello,

I am working on a complicated retaining wall structure for a Bioretention area. I have modeled the structure using plates in RISA-3D. Given the lengths of the walls, I have chosen to implement a strut between walls to relieve the flexural demands on the walls resisting the lateral earth pressures. When designing the walls for vertical and horizontal reinforcement, I am considering the plate moments Mx and My, however I am confused when it comes to Mxy.

My understanding is that the Mxy moments are out-of-plane twisting moments on the wall. Is this synonymous with torsion on the wall? I have never designed a wall for torsion and am quite confused as to how these twisting moments are resisted. Has anyone ever experienced this or have any guidance? Below is a screenshot of my model. Thank you in advance!

 

[WARose]

Twisting moments are generally combined with orthogonal moments to get your design moment. One of the most popular methods to do so is the Wood-Armer method. (You can probably do a search on here and find some threads discussing it.) Personally, I just add the absolute value of the twisting moment to the [absolute value of the] Mx or My moment and run with which ever one is higher. (Which is similar to the Wood-Armer method.)