Stiffness of Masonry Shear Wall (moment & shear) 2

[crozroz0000]

I want the stiffness of a masonry shear wall.

Construction:
Say its 10' tall, 12' long. 8" block w/ #5 @ 24" O.C.

Load:
It has a shear a the top of the wall.

Equation:
I know the bending stiffness is k = P/delta = 3EI/(L^3)

How do I find shear stiffness?
I recall it involves G (shear modulus)

 

[whyun]

Shear stiffness is AEv/1.2L where Ev is the same as G which equals 0.4Em.

I tend to see the equations involving deflection, then stiffness is just the invert.

Delta_c = Delta_m + Delta_v = Ph^3/3EmI + 1.2Ph/AEv
Delta_f = Delta_m + Delta_v = Ph^3/12EmI + 1.2Ph/AEv

Subscript c is cantilevered wall and f is for fixed wall. Shear deflection is the same for both conditions.

 

[crozroz0000]

That is perfect! Thanks whyun

 

[miecz]

The equations cited by whyun apply to a solid wall. If your wall has openings for doors or windows, the formulas need to be modified. Check out the method outlined in Appendix C of the Navy Manual, NAVFAC P-355.

 

[crozroz0000]

Thank you, jmiec

 

[JD2]

I have a two story parking structure approximately 100'x100'. Supporting the 2nd level, I have concrete walls retaining soil along two of the sides (forming an "L") and steel columns and beams along the other two sides. Due to architectural constraints, I cannot use X-bracing in these two walls (only moment frames or knee bracing).

For lateral loads, Is there a way to stiffen the steel frames to try to pull the center of rotation (reducing "e")out away from the intersection of the two concrete legs? Should I even try?

How do you determine relative stiffness when you combine (in the same direction) concrete walls and some type of steel resisting system such as x-bracing, knee bracing or a moment frame - is it based upon lateral deflection? With something this short, it would seem that lateral deflection of the concrete shearwalls would be next to nothing with no way to match that deflection with the steel.

I was thinking about designing the concrete walls to carry 100% of the load (plus torsion) and designing the steel lines to carry say 25% of the of the load (no torsion) and limit their lateral deflection to the allowable story drift given in the Code.

Any thoughts would be appreciated.

 

[UcfSE]

You should start your own thread when you have a new topic. That way we don't take over the OP's thread.