Bill of Quantities, IfcSlab OuterSurfaceArea

steverugisteverugi
in General

IfcColumn and IfcBeam formworks area calculation

in preparing a Bill of Quantities I can get the formwork area of columns and beams using the OuterSurfaceArea from Qto_ColumnBaseQuantites, also available in the dropdown menu in the Elements pane of the Cost Item Quantities

in this simple case the column has 200x400 sides or 1.2m perimeter, each 3m column has therefore a 3.6m2 outer area (total of 4 cols = 14.40 m2 in the BoQ)

the same principle applies to beams, so far so good!

IfcSlab formworks area calculation

Conversely Qto_SlabBaseQuantities set doesn't have similar value, though it can be easily obtained (perimeter x depth)

At the moment I can use the formwork rate adapted to be used on a particular depth ($70/m2 per area or $14/m if applied to a 20cm strip arond a slab)

Questions

  1. is there any other way of entering quantities applying some calculation instead of hardwiring the depth component as I showed above?
  2. Can cost items be multiplied/divided among themselves before being added to a summary cost?

as always, thanks for your kind support

Tagged:
carlopav

Comments

  • steverugisteverugi
    1. is there any other way of entering quantities applying some calculation instead of hardwiring the depth component as I showed above?
    2. Can cost items be multiplied/divided among themselves before being added to a summary cost?

    also needed when it comes to quantifying areas of formworks since they need to be adjusted (beams for instance need their area deducted 2x by the slab thickness if not external and 1x if external..) to reflect their actual quantity

  • steverugisteverugi

    Maybe it's better with an image..

    this is an example of beams used to support a slab (dims are just random)

    and this is the takeoff issue when I use OuterSurfaceArea from Qto_ColumnBaseQuantities

    the red beam is marked as IsExternal the yellow one is not (therefore is internal)

    Question:

    In a Cost Item, how to make use of quantities extracted using beams (or slabs) to factor the adjustment due to

    • slab thickness to be multiplied by perimeter to find formwork area in slab
    • account for slab thickness to be deducted 1x in external beams and 2x in internal beams

    thanks for your help

  • MassimoMassimo

    Questions
    1. is there any other way of entering quantities applying some calculation instead of hardwiring the depth component as I showed above?
    2. Can cost items be multiplied/divided among themselves before being added to a summary cost?

    @steverugi well, regarding question n.2, you can perform math operations with nested cost item.
    First create a summary cost item (lets say A), and then create, for example, 2 nested sub cost item (let's say A.1 and A.2).
    In order to perform math operations with the sub items, you have to define the sub cost item value as category (instead of fixed).
    So for example, define the cost A.1 as category FIRSTCATEGORY and applied value 2.
    After that, define the cost A.2 as category SECONDCATEGORY and applied value 4.
    Then select the summary cost and modify the formula as: FIRSTCATEGORY() * SECONDCATEGORY()
    You will obtain that the summary cost item will be the multiplication between A.1 and A.2.
    You can also ofcourse specify whatever fomula you want ...

  • steverugisteverugi
    edited January 2024

    @steverugi well, regarding question n.2, you can perform math operations with nested cost item.
    First create a summary cost item (lets say A), and then create, for example, 2 nested sub cost item (let's say A.1 and A.2).
    In order to perform math operations with the sub items, you have to define the sub cost item value as category (instead of fixed).
    So for example, define the cost A.1 as category FIRSTCATEGORY and applied value 2.
    After that, define the cost A.2 as category SECONDCATEGORY and applied value 4.
    Then select the summary cost and modify the formula as: FIRSTCATEGORY() * SECONDCATEGORY()
    You will obtain that the summary cost item will be the multiplication between A.1 and A.2.
    You can also ofcourse specify whatever fomula you want ...

    thanks @Massimo always available to assist me :)

    If I am not mistaken we discussed this method in a past thread blenderbim-ifccostitem-composition-2021-yt-video

    I am fairly OK with item cost value operations, it was rather the quantity aspect, like deducting a certain quantity from a different element/item (like slab thickness) to calculate formwork area of a beam.

    In my example above the thickness of the slab needs to be subtracted from the external beam outer area once, or twice from the internal beam outer area. I hope it is more clear now, cheers

    Massimoatomkarinca
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