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CMU Shear Walls

CMU Shear Walls

CMU Shear Walls

(OP)
I am a new RAM user and need a little help

The manual is not very helpful on modeling CMU shear walls or bearing walls. We specify C90 lightweight concrete block with f'm = 1500 psi and the steel reinforcing is typcally #5 @ 48. How should I enter the properties?

Some block shear walls are only connected to the floor slab or roof deck without any connection to the columns or beams. In this case, the shear walls are the only lateral-force resisting members for the structure.

On another job, some of the shear walls are also bearing walls. In this case, the joists run parallel to some walls (non-bearing) and perpendicular to the other walls (bearing). I am expecting to use all of the walls for shear.

I understand that the shear walls should be designated as lateral members and laid out on the wall centerlines. How do I model these CMU walls. Does RAM know or expect the walls to be attached to the nearest diaphragm? Am I missing something?
 

RE: CMU Shear Walls

Which RAM software are you using?  Typically, most 3D analysis programs won't handle CMU walls directly.  And I believe RAM is no exception for their Structural System package.  If you are using RAM Advance, then you can enter you wall as CMU, along with all your floor and roof framing, in your 3D model.  The program will then calculate the loading (in-plane, out-plane, gravity) on the wall, then export each wall to its Masonry Wall Design module.  In here, you will design the wall reinforcing for the calculated loads.

 

RE: CMU Shear Walls

(OP)
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?

The Frame module in RAM SS automatically meshes these walls and allows you to cut sections anywhere you need analysis results.

RE: CMU Shear Walls

You should check out RAM Advanse (Here are some highlights from the last two releases):

•    Masonry Block Database: The masonry block dimensions have been fine-tuned using NCMA TEK 2-1A.

•    Hybrid Masonry (and Steel) Design: Steel frames with reinforced masonry infill walls can now be designed in RAM Advanse. The user can specify different releases between the beam and the wall or between the columns and the wall to account for axial, shear and or moment transfers. This feature was driven by the International Masonry Institute according to their specifications.

•    ACI 530-05: The requirements of the Masonry Standards Joint Committee Code (ACI 530-05/ASCE 5-05/TMS 402-05) have been incorporated for bearing walls, shear walls, retaining walls, masonry columns and lintels.

•    Joint Reinforcement: Wire joint reinforcement can now be specified for masonry walls in lieu of horizontal reinforcing bars. The program can handle ladder type and truss type reinforcements.

 

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