How to connect a beam with a shear wall???

[kellez]

Hello everyone,

I am trying to model a five storey Reinforced concrete structure. The structure is mostly supported by shear walls interconnected with RC beams and a solid slab.
What i am trying to achieve right now is to make the sap2000 model as accurate as possible.

What i mean is that when i create a shear wall of 1.5 meters width the insertion point is in the middles of the wall which is not the case with the real structure
so i moved the insertion point of the wall to achieve the same position as the one of the real structure.

Then i repeat the same with the beams so that the top of the beam is in the middle of the slab and at the top of the columns therefore achieving a composite behaviour.

Next step is the End (offset)length for beams. I have a 1.5 meter long shear wall connected with a beam 4 meters long which in reality is 2.5meters long therefore i
offset the beam 1.5 meters to achieve this. Now the problem is that when i run the analysis and check the deformation of the structure the beam is not actually
connected into the shear wall and the wall and beam deform independently.

How can i set the connection of the beam at the start of the shear wall and not at the insertion point? please see the picture below to understand what i mean.

 

[kellez]

http://i58.tinypic.com/23jj3tc.jpg[/IMG]]

 

[kellez]

anyone?

 

[stressed]

kellez, I'm not sure you understand how the insertion point and end length offsets work. Insertion point, in this example would typically be used to assign top center of your beam. You didn't mention which element type(s) you used. Did you model the beam using a beam/frame element? If the beam was modeled as a beam/frame and wall modeled using shell elements, why not connect the beam directly to the wall joint(s)?

 

[kellez]

The beam and wall are both assigned as frame elements, so i should model the wall as frame element?

 

[stressed]

That was an important detail that you left out in your initial posts, particularly because your screenshots were in extruded view which leads people to think the wall was modeled with shell elements. Usually walls are modeled with shell elements. If you want to model the wall using a frame/column element, then draw your beam to the point where you want to connect at the outside of the wall, a point which would be disconnected from the column half the width of the wall. Attach beam end point to the column by selecting beam end joint and column joint, then assign a joint constraint (Body type). The joint constraint will account for the offset distance (and resulting moment differential) between wall/column centerline and the beam end point.

If you modeled the walls using shell elements you wouldn't have to worry about assigning joint constraints because you could connect directly to the shell/wall joint(s). With shell elements, you would need to mesh in order maintain proper connectivity and to obtain reasonable results, probably dividing the mesh areas to be 4' X 4' or smaller. You can add gridlines and mesh by gridline to help you define mesh lines for connectivity.

 

[kellez]

Thank you for the great information, i will try to model the wall as a shell tomorrow and see how it goes.

 

[kellez]

Hello stressed, i followed your instructions and modelled the walls as shell elements. I carried the analysis at this stage and the beams are not connected to the walls which was expected.

I am not really sure how to connect beam-walls using your proposed approach by mesh.

However i tried something different, i have assigned edge constraints to all walls (create constraints around object edges). I run the analysis and the beams are now connected to the walls, however i am not sure if this is the correct approach.

Something i have noticed is that with this approach the beam is not completely connected to the wall, the cross sectional area of the beam is not fully connected to the wall. The beam and wall are only connected at the insertion point (grid point)

 

[stressed]

kellez, if your beam was not connected to the wall, that means that you did not draw the beam to connect to a shell joint. It's as basic as that - the wall must have a mesh point where it connects to the beam or there will be no connectivity.

Edge constraint is an approximate method that works well if joints are close together, but doesn't work so well if joints are far apart. Since you are learning how to do basic modeling, I would recommend that you learn how to properly model without relying on edge constraints. Use Joint constraints if you're modeling with column/frame walls.