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
  • Ram_STAAD,

    This is the answer to your question on whether there is something you may have overlooked:

    For FLOOR LOAD, there are 2 methods:

    1) The region over which the load acts is defined by XRANGE, YRANGE and ZRANGE each of which takes on 2 numbers - a min value and a max value. Those 6 numbers form the edges of a box inside which the loaded zone lies. Additionally, one has to specify the load intensity (pressure) and the direction in which the load acts - global X, global Y or global Z

    2) The members which receive the load are clustered into a group called a FLOOR GROUP as sasa3k mentioned. There is less of a chance of any member going unloaded using this method. For this method too, one has to specify the load intensity (pressure) and the direction in which the load acts - global X, global Y or global Z

    If you have specified all these required values, your input is correct, provided that the members inside the region form closed boundaries.



  • Hello Kris.

    The technique that I employ is to calculate the tributary width for each beam on which the loading area spans and multiply the same with the applied pressure. Then I have on my hand a Uniformly Distributed Load applied on the members that support the load area. I am not sure why STAAD has set limitations on the applicability of area loads on closed panels alone. In the end, I am certain the program does the same thing that I do. determine the influence width of beams, multiply it with the applied pressure.

    The corner co-ordinates of the rectangle specified essentially demarcates the boundary with in which the load acts. The geometry of loaded area is therefore very clear. Please note that I am applying neither on a inclined surface nor on a skewed geometry. I am essentially applying my loads on regular rectangles.

    As I understand it, utilising the One Way load distribution is the more practical way of simulating the situation.

    The manual on this very clear, I will read it again and again if need be. What I do not understand is why should the specified rectangle be within a closed panel.

    If the process involved is determining the tributary width of the beams on which the area spans, multiplying it with the applied pressure and applying the associated UDL on the beams, what is the factor that necessitates the use of closed panels?

    I am by no means stubborn and if there is a way for me to work around this issue, I will. I wanted to implement sass3k's suggestion. The only thing I am worried about is that it will seriously screw up my model if I introduce dummy beams now. (I have beams that are on top of each other and hence specified with definite member offsets). Still, it's better than calculating the member loads manually.

    I will post a pic early tomorrow showing how I calculate the tributary width.

Reply
  • Hello Kris.

    The technique that I employ is to calculate the tributary width for each beam on which the loading area spans and multiply the same with the applied pressure. Then I have on my hand a Uniformly Distributed Load applied on the members that support the load area. I am not sure why STAAD has set limitations on the applicability of area loads on closed panels alone. In the end, I am certain the program does the same thing that I do. determine the influence width of beams, multiply it with the applied pressure.

    The corner co-ordinates of the rectangle specified essentially demarcates the boundary with in which the load acts. The geometry of loaded area is therefore very clear. Please note that I am applying neither on a inclined surface nor on a skewed geometry. I am essentially applying my loads on regular rectangles.

    As I understand it, utilising the One Way load distribution is the more practical way of simulating the situation.

    The manual on this very clear, I will read it again and again if need be. What I do not understand is why should the specified rectangle be within a closed panel.

    If the process involved is determining the tributary width of the beams on which the area spans, multiplying it with the applied pressure and applying the associated UDL on the beams, what is the factor that necessitates the use of closed panels?

    I am by no means stubborn and if there is a way for me to work around this issue, I will. I wanted to implement sass3k's suggestion. The only thing I am worried about is that it will seriously screw up my model if I introduce dummy beams now. (I have beams that are on top of each other and hence specified with definite member offsets). Still, it's better than calculating the member loads manually.

    I will post a pic early tomorrow showing how I calculate the tributary width.

Children
  • Hello again Kris.

    Just wanted to post the info right away.

    The concept we use to determine the tributary widths of beams on which we have loaded areas is as shown below.

    It's not very pretty, but it's the best I can manage right now. The concept is to define a simple beam element with support points that correspond to the centre lines of our loaded members. i simply load it with a unit load, run the analysis and obtain the reaction loads. The reaction loads at the support points essentially signify the influence widths of individual members in appropriate length units.

    It might not be a false proof method of working it out. But it falls within the acceptable range of tolerance and is a simple way of doing it.

    It's a easy matter then to multiply the influence width with pressure and arrive at UDLs on the beams.

  • Sincere apologies Shany.

    I am no longer authorised to access RSTAB at work. So I have to reach home to do what I promised. And my wife hates me for taking work home. :(

    This is what I had in mind.

    Can we do the same with STAAD?

    What am I missing here?

    For all its flaws, STAAD is such a robust performer. I haven't had a single program crash since I began using it. Not a single one. (OK except for cases when I would mess around with mesh refinement). I downloaded RSTAB, just did that simple model and the display driver crashed. :(

    cheers.