CMU Shear Wall Analysis

[SteveGregory]

I have RAM Structural System v.13. The program allows you to model the structure with concrete, masonry or other shear wall types. I do not have the license that does the concrete shear wall design. However, RAM SS Frame module will analyze any shear wall as long as you input the "correct" properties. The shear wall design from the analysis will be manual.

The program is looking for E, thickness, density and Poissons ratio. For our typical jobs, E=1,350 ksi for f'm=1,500 psi strength masonry. Should I use this E or some percentage reduction for cracking and what about Poisson?

 

[DaveAtkins]

I don't think E should be affected by cracking.

I don't think Poisson's Ratio matters that much.

DaveAtkins

 

[SteveGregory]

Modifying the E to an "Effective E" seems to be the only good way to adjust the stiffness of the masonry shear wall to a realistic value.

This may not make any difference when all of the lateral resistance is in the form of shear walls. But it could make a big difference in a building with a mixture of shear walls, braced frames and steel moment frames.

The other possibility is modifying the wall thickness to an "effective thickness". Although the thickness of the wall contributes to the wall stiffness, it is also used by RAM for self-weight calculations.

 

[concretemasonry]

The 1500 psi f'm is about as low as you can get. I have been involved with 4500 psi hollow (about 52% solid) prisms.

Dick