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Without the priority system the modeling of floors would require one of two methods:
Yes.
Note: It is important that you do not abandon the process after pasting. Otherwise, you will have two supports below at various locations, which causes calculation errors.
Choose Layers > Element > Slab Summary Plan or go to the visible objects dialog box and check the "Outline only" option under slab elements.
There is no difference unless you modify their behavior. See discussion of behavior in “Slab area properties” on page 56 and “Beam properties” on page 57. The difference in only in the modeling, a beam always has two parallel edges offset from the two end points, while a slab area polygon can be any shape in plan.
There is no limit, other than the limitations of your computer. If you find the program performance too slow, consider any of the following to help:
This cannot be answered directly as it depends upon the structure and loads. The maximum is 32.8 feet (10 meters). To speed the analysis, it is useful to choose a coarse mesh for preliminary design and a fine mesh for final design.
If in doubt, you should investigate the effects of different mesh element sizes.
Depending upon the defined fixity, columns can provide rotational and lateral restraint. If the far end of a column is defined as a “roller” support (or both ends of the column are pinned) then the column does not provide any lateral restraint to the slab. Columns above the slab do not support the slab vertically, they can only restrain the slab rotationally and laterally.
Columns in Ram Concept connect to the slab finite element mesh at a single node located at the column centroid. They are not solid objects nor do they provide vertical support to multiple nodes. This is apparent viewing the Elements - Standard Plan.
As such, deflections in the slab start from that node and increase towards the face of the column. For small columns this may not matter much, but for large area columns this is significant.
To mimic the behavior of a stiff column support, we suggest modeling a thick and stiff slab object that overlays the column volume like a mini-drop cap. Be sure to assign a higher priority to this patch of concrete. It is recommended to model this patch with an elevated top of concrete elevation such that the slab centroid aligns with the mid-depth of the patch in order to avoid eccentricity at this joint.
The same approach could be taken for thick walls supporting the slab as well. A beam or slab object can be used there.
The general preference is to model the beams through the column, extended to the slab edge since it best matches the built condition and how things are formed. Stopping the beam at the column centerline results in a slightly more flexible system.
Yes, if you select Shear Wall as a property. If the Shear Wall is unchecked then the slab is allowed to slip freely over the top of the wall. The walls rotational stiffness is independent of the Shear Wall setting; use the fixity settings to control the walls rotational stiffness about its longitudinal axis.
Wall elements can be used to model the stiffness and spanning ability of walls connected to the slab. Walls above behave similarly to beams in that they stiffen the floor. One could actually model the walls above the slab as beams instead, but it is not generally recommended.
Using beam or slab elements does have some advantages over using wall elements (“wall-beams”):
When modeling wall-beams above the slab, Concept interprets some of the wall element parameters differently than for walls below.
Wall-beam elements have one advantage over slab elements.
There is no restraint at the far end of a wall above. (Even if “Rotationally Fixed at Far End” is checked, it is ignored).
You can reduce the tension by iteration. The tension gets closer to zero with an increase in the number of iterations. See “Zero tension iteration options” on page 126 for more information.
The geotechnical engineer commonly provides a value called the “subgrade modulus” or “modulus of subgrade reaction”. As a guide only: realistic values vary from 100 pci (approx. 25 MN/m3) for soft clay to 750 pci (approx. 200 MN/m3) for very dense gravel.
Note: Area springs are always assumed to be compression only springs in the Z direction, but they behave elastically in the R and S axes. Line and point springs are also linear elastic supports resisting tension or compression.
Yes, soil area spring stiffness values are cumulative. If you model two area springs with 100 pci stiffness you will get 200 pci stiffness in the intersection.
Not directly. You could draw spring supports that approximate varying soil support.
No, but it is a good idea. It ensures a node is placed at that location where there is likely to be a heavy point load. The columns also provide convenient snap points for tendons or design strips.
Yes. Use either (flexible) columns under, or point springs. Skin friction is not considered.
Yes, but the results could be very susceptible to variations in geotechnical parameters. For example, if the soil’s stiffness is overestimated, the actual pile reactions could be significantly underestimated. Use caution.
No. An oversized area spring is fine. The program applies the individual nodal springs based on the mesh tributary area.
Yes. You can vary the stiffness in two directions. See “Area spring properties” on page 55.
This is not an input parameter. You need to look at soil bearing pressure plans (which have a maxima / minima legend) to assess the maximum pressures.