Bearing Walls vs. Building Frames

[palves]

I'm looking at Table 12.2-1 in the ASCE7 and see that "Special Reinforced Concrete Shearwalls" can be used as both a Bearing Wall or a Building Frame system. I never would think to classify a concrete shear wall as a bearing frame system, but can anybody give me real world examples of the differences between the two? Because of the different R factors the bearing frame system would be more advantageous and I would like to use that if I had the choice.

 

[WillisV]

http://www.gostructural.com/print-magazinearticle-code_simple__asce_7_05_table_1-4940.html

 

[JAE]

Read WillisV's link - basically it defines the difference - that being that shear walls can work in both systems - one where the walls themselves support the majority of the gravity loads and the other where the frame supports the gravity loads and the shear walls primarily take the lateral forces...but may support some limited gravity loads.

 

[palves]

Thanks guys. That article really helped out. I was thinking along those lines, but thought it a little unusual to detail beams and columns integrally into a concrete wall in order to satisfy a "building frame" definition. Other than the decreased R value are there any other advantages to adding those integral members into the wall? The 2 examples given in the article were relevant to high rise structures (not my area of expertise) so maybe there are some other considerations there that I'm not thinking of.

 

[palves]

I meant to say either "increased R value" or "decreased base shear". Two different thoughts mixing together.

 

[Teguci]

I remember that very question being asked in one of Ghosh's classes I took. This response is better.

Just to add my own interpretation:
Design a fully framed structure that takes all vertical loads (columns and beams are detailed to the corresponding level - ordinary, special..). Add reinforced infill walls (again with appropriate detailing) to take the lateral shear loads. During a seismic event assume the shear walls will crack and fail in shear tension, but will still be present to provide a diagonal compression strut to prevent full building failure. This shear failure will allow more seismic force absorption (larger R value) and higher deflections (larger cd factor).

The two concerns not covered is dealing with the resultant compression strut into the framing members, and weak story effects after the ground floor infill panels have initially failed.

This reminds a lot of confined masonry thats used in Central and South America. Have a look.

http://flyashbricksinfo.com/constru...onry-buildings-resist-earthquake-effects.html