AREA LOAD and FLOOR LOAD

Hi Good Day STAAD GURUs

My questions are:

 1. When using the AREA LOAD or FLOOR LOAD to represent the load beeing carried by the slab does STAAD automatically convert those loads to equivalent loads and then automatically impose those equivalent loads to the beams bordering the slab? or do i have to manually solve for the equivalent load then manually impose those loads (from the slab) to the beams. Actually thats what our instructor taught us, manually solve the equivalent load then put in on the beams supporting the slab. but doubt it[*-)]

2. On the command  "selfweight -1" does that selfweight include the weight of the slabs even if the slabs were simply modeled as plates?

ex: ....

meter kn

Element Incidences

1 1 2 3 4

Element Property

1 thickness 0.15

3. Attached file shows how to correct improperly connected plates. We added nodes 9 and 10 to beam 1 4 supporting plate 1 to correct the improper connection of plates 2 and 1. Just for discussion purposes lets us consider PLATE 1 before we break it into 3 plates as a TWO WAY slab. After breaking it to 3 slabs, the resulting plates from plate 1 are plates 3 4 and 5. Sir/Ma'am if i'm gonna load these slabs using FLOOR LOAD / AREA LOAD. Do i have to load them individually as one way for plates 3 and 5 then two way for plate 4? or should i just apply the floor load over these plates?

Thanks a lot

Mac

 

Parents
  • Hi,

    1.

    When you apply a floor load to a slab pannel, the programme calculates the equivalent load and apply the load to the beams bordering the slab as a uniformly distributed load. You do not have to calculate the equivalent load manually and apply them to the beams. Like in the attached figure a floor load of 10kN in the –GY direction is applied on the slab and the programme converts the load to equivalent distributed load and apply them to the beams.

    Basically, the commands like Floor load or Area load are used when the entity transmitting the load, such as a slab, is not part of the structural model. The Area Load or One way Load may be used for modeling one-way distribution and the Floor Load may be used for modeling two-way distribution. For details please go through the Technical Referrence Mannual section 5.32.4.

     

    2.

    If you want to include the self weight of the plates then you have to assign the plates to the Self Weight command. The self weight command include the self weight of every active member and applied as a uniformly distributed member load.

    The self weight of a plate is placed at the joints, regardless of plate releases. If you want to transfer the load from the plate to the connecting beam as a uniformly distributed load then you have to mesh the plate.

     

     

     

    3.

    As in your case you use plates in your model. So it is preferable to use “Plate Load” command in place of Floor Load or Area load command.

    It is preferable to assign an area load for a one way slab. But there is no strict rule about this. You can assign a two way load also for those pannels.

    If in your structure there are a number of one way slab, then you can create a Floor group considering those slabs and assign a one way load distribution for them. 

     

  • Good Afternoon Ruddranil.

    I would like to ask something about Plate Load because you mentioned it in your above reply.

    I modeled a Mat foundation using plate elements. And I have an Equipment Foundation on top of the Mat Foundation. Can you teach me which kind of load is much better to use Area Load, Surface Load or Plate Load. Because I cant find any explanation in the Help menu about the difference of this load type. And since I used Plate elements in my mat fdn i just used the Plate loads command.

    In the Plate Load command menu, STAAD ask for the local and global direction of the loads. SInce my load is just the weight of the foundation I have the Y-Direction only, but Im confuse with the Local Y and GY(i suppose this is Global Y) directions. Which one should I use?

    Thanks.

  • For specifying loads on elements , use the PLATE LOAD option . The area load command is now not used any more, it is superseded by the Floor load command , which is a better method of distributing the slab load to the beams .

    Every member and plate has its own set of axis . Now the load may be applied to the member / element as per the Global Axis ( denoted by GY GX GZ) or the local axis of the individual member .

    Right click on the GUI, go to Labels and check in the option to see the Beam Orientation and Plate Orientation



  • Greetings Shany.

    Is there a provision in STAAD to apply an Area Load on the Structure by simply specifying the bounding plane within which it must be applied? 

    Please see the attached file for RSTAB. 

    I just specify the magnitude of the load, the direction of the load and specify which Area the load has to act.

    I have seen the Floor Load, One Way load and Area Load in STAAD and they are too complicated a way of putting the loads in.

    If there is a way in which I can simplify this, I will appreciate it if you can tell me.

    Cheers.

Reply
  • Greetings Shany.

    Is there a provision in STAAD to apply an Area Load on the Structure by simply specifying the bounding plane within which it must be applied? 

    Please see the attached file for RSTAB. 

    I just specify the magnitude of the load, the direction of the load and specify which Area the load has to act.

    I have seen the Floor Load, One Way load and Area Load in STAAD and they are too complicated a way of putting the loads in.

    If there is a way in which I can simplify this, I will appreciate it if you can tell me.

    Cheers.

Children
  • How far accurate an approximation would it be if I specify thin surface elements where I need my area loads and apply those loads on those surfaces as surface loads rather than Area loads?

  • Hello RAM

    I am not sure why you are finding the FLOOR LOAD command complicated, but I guess its very easy to use. You just need to specify a closed panel using the X Y and Z Range and give in the load intensity, the rest is done by the program.



  • Shany,

    The objective is to work around the tedium of calculating individual member loads (based on tributary widths)  for each and every member subjected to a pressure load.

    Please see the attachment. As per the STAAD convention, I need to specify the co-ordinate values of each and every of those rectangles (in colour) and later on specify the direction in which the load should be considered (one way loading - 'towards'). Honestly, that is mind boggling when considering I have quite a lot of those closed panels you mention. And the program requires me to enter the corner co-ordinates of each and every of those rectangles for it to apply the corresponding member load?

    You might have noticed the delay in my reply. That's because I have been calculating those member forces manually!

    Seriously, I believe there is another way around it that I have missed.

    In RSTAB, it is possible for me to specify a bounding plane with four nodes, specify the load magnitude and specify the members that are associated with the loading. I can simply copy paste those nodes without calculating their co-ordinate values!

    Can I do something similar in STAAD?

    cheers.

  • I suppose it will no do harm to explain the design environment.

    The objective is to impose access loads, loads of chillers etc. etc. on say gratings laid over steel joists/girders as area loads. The design situation is thereby different from the slab loads you had in mind. There are designated areas meant for storage, designated areas meant for superimposed loads, areas where we have a combination of both etc.

    The loading is therefore not uniform! Not in magnitude nor in the size of area to which it is confined.

    It is not a complicated thing by any means, but if one has to calculate those forces manually after determining the tributary widths of individual members, it becomes very tedious.

    I tried to work by determining the co-ordinate values and entering them. But STAAD repeatedly gives me the message "Load cannot be generated".

    The way I see it, STAAD requires me to enter the ranges or corner co-ordinates of those rectangles, the magnitude and the direction towards which the force should act. Despite doing all this, I am still stuck at the Load cannot be generated stage.

  • Just a typical design scenario for me Shany.

    The line layout represents the loading area.

    Can you please suggest a way to achieve it?