surface load

[farukpolat3535]

I am modelling an existing building and I have wondered that How can I apply surface load or area load my floors Instead of applying beam uniform load.

[Clarabella]

Dear Faruk,
you can use the command surfaceload. See the attached picture

surface.png (14.51 KiB) Viewed 4977 times

Regards

[farukpolat3535]

Firstly thank you for your answer and your kindness. I would want to know that should I apply the load to a master node or is there any oher option to apply that load ? For instance in Etabs you can draw a slab and you use this slab for loading. But in stko we just create a diaphram and master nodes and I suppose that I should use master node to apply slab load am I wrong ?

[Horace Horsecollar]

Could you please explain what you would like to do?
For the gravity load, you can apply the loads to the nodes, edges, or surfaces. If you like to perform a pushover analysis you can use (if you have a rigid diaphragm) a master node and apply there the load.
Please describe your problem and we will try to guide you

[farukpolat3535]

I want to apply the surface load to the floor. But I have just rigid diaphram and master node at the center of diaphram. Lets say 2KN/m2 we have on floors and when I open the condition tab +loads+generic+Surfaceload there are 3 quetions for me
1) one way or two way means that behaviour type of slab ?
2) unsupporting selection set is the area borders of my slab ?
3)and projection box What is it used for?

Regards

[STKO Team]

1) one way or two way means that behaviour type of slab ?

1 way means that the slab is able to carry load only in 1 direction, so only the beams orthogonal to the slab direction will be laoded.

2) unsupporting selection set is the area borders of my slab ?

Sometimes you need to draw internal small beams in your slab, that however are not supposed to carry the vertical load. In this case you can tell the floor load not to put load onto those beams using this selection set.

3)and projection box What is it used for?

Projection is only useful when your slab are inclined with respect to the XY plane. By default the pressure load is referred to the real area of the surface slab. If projection is checked, then the pressure load is referred to the projected are onto the XY plane.

Here is an example of a simple 1 floor 1 bay building loaded with a 1-way foor load.

FloorLoads.zip

(99.84 KiB) Downloaded 267 times

As you can see from the image, choosing 1-way, and direction = 90°, the 1-way slab direction will be = Y, so only elements 2 and 4 will be loaded. The pressure load (2 kN/m^2) will be automatically converted to equivalent beam loads with a Wz = 4 kN/m (since the slab size in the Y direction = 4 m)

fload_2.png (21.93 KiB) Viewed 4951 times

fload_1.png (96.68 KiB) Viewed 4951 times

[farukpolat3535]

Thank you for your answer. I tried to do the same thing that you sent me to my existing building but there is a problem about faces. Firstly I created using with Face3/4 command for my rectengular slabs. After that I realise I can't create slab which has more than 4 vertex with this command and I tried to use Planar as you can see on my model. But when I need to get tcl there was something going wrong about distributing load to the beams. I would be happy ıf you answer my question.


Best Regards.

[marafini.f]

Dear faruk,

Thank you for notifying us of the issue you encountered. The surfaceLoad application for non rectangular faces is in fact a method we are still developing, as a re-partition rule which can encompass all possible shapes is quite complex to implement.
As for your current issue, unfortunately, you can use the surfaceLoad only on rectangular faces.
On a side note, we noticed your faces and structure frame are separated in terms of geometry, remember you have to merge everything for the model to be interconnected.

We will be developing the surfaceLoad command further and update you on the progress.

The STKO Team

[farukpolat3535]

Thank you for your answer. I Merged my model and I made some changes. Firstly I have changed locations of some columns and beams. Secondly my slab shapes are became rectangular type. I use 3/4 face commend for all slabs. But when I need to get tcl there is an error shown in picture. Face 0 defined a two-way floor but is not rectangular. Can you help me about it.


Regards.

[marafini.f]

Dear faruk,

Shapes with more than 4 vertices are not considered rectangular by the surface load command, each border segment is part of the shape, and the script that is implemented for now requires 4 borders/lines with 4 vertices.

If you really want to continue with the surface load in this type of structure you'll need to portion the structure even further, and obtain 4 vertices rectangular shapes. But I have seen that you choose to model the beams with a concentrated plasticity approach, this does not work if you for example portion a beam in two, you'll have a hinge where you don't want one.
Moreover, you see that the mesher created nodes in the center of the face, and even if you apply a structured mesh, you will still have problems with additional nodes or missing faces (when elements are not meshed, they kind of disappear in the mesh view in STKO, to signal that it couldn't build a coherent mesh). These floating nodes are not part of your structure, so you'll have a singularity when you manage to run your analysis.

You are at a crossroad: you can either calculate your load by hand for each slab and apply edgeloads (you could test your skills in the Python API and develop a script to do the calculations for you, we can support you in that) or you can model your slab as a shell element.

(On another side note, when you changed all your beams you forgot to re-apply the element properties, remember they get lost most of the time when you alter the geometry).

Let us know how you decide to progress.

Francesca