STAAD Pro modeling - Structural Analysis and Design - Forum - Structural Analysis and Design - Bentley Communities

## Structural Analysis and Design

This is where you can find and contribute to discussions, ideas, and other information about Bentley Structural Analysis and Design products.
Structural Analysis and Design - Forum

• Could anyone correct me on the way of modeling? I have a slab with 300 mm thickness and beams at the soffit of the slabs. Beam sizes are 300 mm x 600 mm. I attached the simple STAAD Pro model in order to get the idea.

My doubt is whether I need to move the beam coordinate, as you can see from the Figure 1. The centroid of the beam is similar to the centroid of the slab as well. Do I need to move the beam coordinate downwards? If yes, there will be a gap between the nodes or elements. They are not connected. In that case, how to deal with this?

Figure 1

Another doubt is when I create a plate; the plate is a flat element (without thickness) as shown in Figure 2.

Figure 2

When the thickness is added as shown in Figure 3, the surface of the slab will go above the zero at Y axis. The thickness is added 150 mm above and below Y axis. Do I need to take this into account? So, am I required to move the slab coordinate as well based on the thickness of the slab? It is because I will need to add beam at the soffit of the slab, I wonder if I need to take note of these issues.

Figure 3

Best regards,

Takila

• The matter can be addressed by shifting the start and end node of  the beam in negative direction of Y and then connecting the same to the slab with master and slave command, but this process will prove to be very very tedious.In your case it would be better to adopt member offset for the beam in the negative of Y direction in order to make the beam and the slab at the same level and remain connected to each other.

All members in staad are connected at the centre line or you can say at the cg of the section. That is why it looks so. In 99% cases there is no need to take care of these issues. In steel structure it becomes important in certain cases if one wants a very precise design.

• Thanks for your reply. When I used offset function, the model showed dash line at the offset distance. What does it mean?

And, what are the difference between master slave and offset function?

Best regards,

Takila

• Dash line is the rigid connection between the two objects of the structure without altering the location of the member/element. For master slave better you refer to Staad manual.

• Alright. When I moved the beams, the nodes and supports will not move. Is this scenario normal?

Best regards,

Takila

• When you moved the beam additional node was not created. The node remained at the original location, only the object shifted.

• I see. So, that is normal situation? or i need to move the nodes? because the support will stick to the nodes. Support is not moving as well.

Best regards,

Takila

• You neither need to move the support nor the node.  The beam will be now  designed for the revised span otherwise earlier it would have been designed for the moment considering the centre to centre span.

• I see. Thanks for your information.