I have a Validation > Model > General > “Opening in slab above member” warning. Why do I get this and how do I resolve it?
Question
I have a Validation > Model > General > “Opening in slab above member” warning. Why do I get this and how do I resolve it?
Answer
An Opening in slab above member validation warning occurs if you have defined an opening in a slab that cuts into a concrete member. Tekla Structural Designer will allow you to place an opening anywhere on a slab - this includes cutting into a member, however, no account is taken of this. There is no reduction in the column/beam/wall section area to account for the opening. Because of this, Tekla Structural Designer warns about it - it is then engineering judgement what - if anything, is done about it.
If we hover over one of the problem items a tooltip is displayed “Opening does not cut into the member below the opening”. This indicates that the opening does not remove the material from the member.
We can double click the “Opening in slab above member” warning, a branch or an individual item listed under the branch. If the items exist in the active view they will be highlighted. If they do not exist in the active view then Tekla Structural Designer will automatically switch to the 3D Structure view regime and highlight the openings and members selected. Alternatively, you can right click and choose Highlight Items from the context menu.
Double clicking the branch Opening in slab above member identifies all the issues of this type in the model.
Double clicking the reference SO X, WX or SO X, CX or SO X, LBX selects the objects with the issue.
Where:
SO = Slab opening
W = Wall item
C = Column item
B = Beam item
L = Level
X = Object identifier, a unique number counter.
Issue 1 - Slab opening partially inside a concrete column
Issue 2 - Slab opening over a concrete beam
Issue 3 - Slab opening over a wall
It should be clear that the slab thickness cannot be cut out where the identified member exists. You can either ignore the warning accepting that the slab is not cut at the highlighted locations or you can amend the position of the opening so that it falls completely within the slab boundary outside of the member*
*Validation checks that the slab opening lies outside the perimeter of a concrete column. For beams and walls it checks that it does not cross the wire of the member.
Solution for Issue 1 - Slab opening within a concrete column
For the opening identified partially within the perimeter of the concrete column, to resolve you can select the slab opening and via the Properties window amend the size and/or position to ensure they do not collide.
Please note that it is good practice not to locate an opening incredibly close to, but not quite, at the column perimeter producing a small sliver of slab. This is because of possible meshing issues. Refer to the linked article in the right panel “How do I resolve meshing and mesh quality errors or warnings?” Therefore, ensure the opening is sufficiently within the slab so as not to obtain a mesh warning.
Solution for Issue 2 - Slab opening over a concrete beam
In the screenshot below the opening does not extend downwards into the adjacent slab region as much as shown previously. We do often see modelling of this nature, perhaps an error/oversite, or the model has been generated from another building information modelling package (BIM). Here, the opening on one side of the beam extends within the flange width of the beam itself.
As before to resolve, select the slab opening and adjust the Size/Position of the opening via the Properties Window.
Solution for Issue 3 - Slab opening over a wall.
Following the same principle as the other issues, the opening either sits over a wall or a beam and is therefore identified as a warning for your information.
The screenshot below, shows three highlighted areas (yellow, blue and red) where the opening extends over the three walls forming the C-shaped core wall.
While the issue could be resolved in a similar manner to issue 1 and 2 - by amending the size/position of the opening via the Properties window. It would be better modelling practice to consider smaller slab panels by using the Slab Split/Join commands to break up the single panel thus leaving a void, rather than using an opening.
Original modelling - Single flat slab panel with an opening defined within it.
Optimised modelling solution - Slab panel broken into smaller panels and panel omitted within C-shaped core wall.
This has a number of advantages including the ability to allow for pattern loading and a more optimised reinforcement design.
After making the amendments above. No validation warnings of type Openings in slab above member are reported.