Slab Design Settings

Slab Design Settings

General

Slab design setting is important to preset before starting to design any slabs. Presetting these design parameters can save users significant amount of time. This is to ensure the slabs are correctly designed based on the project criteria.

To access the Slab Design Setting, user can go to "Building Setout" tab > "Settings Center" > "Slab".

Design

Basic design settings are controlled on this tab.



  1. Support Top Steel : To define top support bars extension length calculated from inner surface of support. These multipliers are applied to the span lengths of the slabs. Also, user can define minimum of moment of span to be taken into account in designing the slab.
    1. Extend by 'd' :  Extend length of top support with slab depth, d.
  2. Slab Span Lengths in Analysis : Choose either "Use Clear Span" or "Use Centerline Span" (spans calculated between centre-line of beams) as slab span length for slab strip direction.
    (Transverse direction will always use clear span")
  3. Parameters : 
    1. Ribbed Slab Filler Blocks Unit Weight : To set unit weight of filler blocks when ribbed slab s-block used.
    2. Slab Steel Concrete Cover : To define depth of concrete cover for slabs.
      If you leave this field as zero then the concrete cover will be determined based on active codes.
  4. Column Node Interpretation (FE Strip design) : Option to define stress concentration effects when FE strip analysis is applied. For more detail refer section below. 
  5. Slab Design Combinations : Option to include/ignore lateral combination in slab design.
  6. Wood-Armer Effects in Design (FE design) : To have the design moments to include the torsion effects based on Wood and Armer methodology in slab design. 
The conception of determining equivalent moment is authored by Wood and Armer which takes into account twisting or torsional moment, on top of the pure bending moment in the principal orthogonal direction. Details concerning the method can be found, for instance, in R.H.Wood, "The reinforcement of slabs in accordance with a pre-determined field of moments", Concrete, February 1968, August 1968]. We recommend users consider the Wood-Amer effects in the design of slabs as it is generally recommended by most design references. 
  1. Ribbed Slab Result Collection : Options are "From All Rib Lines" or "From Closest Rib Line to the Strip"

Rebars

Steel bar selection and layout settings are controlled on this tab.


  1. Steel Bar Selection : 
    1. Slab Steel Pattern : To choose slab rebar detailing pattern which shows on plan view.
    2. Min. Steel Bar Size : To set minimum allowable slab rebar size.
    3. Bar Spacing (Min/Max) : To set Minimum and maximum steel bar spacing for slabs.
    4. Steel Bar Spacing Step : Steel bar spacing values will be incremented by the amount specified in this field during iterations.
    5. Steel Bar Length Step : Steel bar lengths values will be incremented by the amount specified in this field during iterations.
    6. Steel Bar Edge Clearance : To specific parallel distance between slab steel bars (ie. first/last rebar) and the edge of the slab.
  1. Curtailment : 
    1. Make Bob for Top Steel Cantilevers : To allow top steel bars in cantilever slabs end with bend of bar. Otherwise, the steel bars will end as straight bar at the end of the cantilever slab.
    2. Put Slab Support Bars to 1st Layer in Both Directions : To put all the support bars to 1st layer at both direction. Otherwise, the program will determine the layer of the bars based on the slab dimensions.
    3. Curtail Support Bars Based on Short Edge Length : To use short edge slab length Lx as the effective length for curtailment extension length calculation (Refer to Slab Design Setting > Slab > Design > "Support Top Steel").
    4. Extend Support Bars Symmetrically When Slab Spans Vary : To extend the support bars symmetrically at inner support to the slabs. If this option is checked, larger effective span length is used to calculate the extension length of the support bar.
    5. Put Bent-up Bars Along Long Edges of One-way Slabs : By default, bent-up bars are not placed along the long edges of the one-way slabs. Check this option to put bent-up bars along the long edges of the one-way slabs.
    6. Slab Steel Bars Cut Length : To enter the cut lengths of the steel bars. The length of the bars will then be checked against this value. Rebar exceeds this length will provide a lap.
    7. Default Bob Length : To set default bend of bar length for slab rebars.

Appearance

This tab is used to control how the steel bars are displayed.

  1. View : 
    1. Print Steel Bar Total Length : The length of steel bar will be printed beside of Bar Label.
    2. Show Steel Bar Span Lines : This option shows the line of spanning range of steel bar.
    3. Show No. of Bars in Bar Label :This option shows the number of rebars in front of the bar label.
    4. Print Alternative Layer Information (B1==BB, B2=BT, T1=TT, T2=TB) : This option will change rebar marking from number into alphabet in the back of bar label.
      Following texts will be printed as steel bar layer information:
      1. TT: 1st Layer of Top Steel (T1)
      2. TB: 2nd Layer of Top Steel (T2)
      3. BB: 1st Layer of Bottom Steel (B1)
      4. BT: 2nd Layer of Bottom Steel (B2)
  1. Transverse Rib Insertion Conditions : A transverse rib will be inserted to one-way ribbed slabs if the first limit is exceeded and a second rib will also be inserted if the second limit is exceeded. This option can be activated using the properties of the slabs.
  2. Slab Hole : To indicate slab hole on drawing by either present as "X" or "L".
​

Column Node Interpretation



Since columns are modelled using a single node and walls are modelled using a series of nodes, undesired stress concentrations may occur on these locations, resulting unexpectedly high support moments. Only a single negative and positive maximum moment are returned from “Fixed Band” slab strips. The area covered by these strips is designed using a single top and bottom steel to resist these moments. When the column nodes are considered in the design, all the area covered by a Fixed Band Strip will be based on a very high moment.

Following options may be used alternatively for taking into account the stress concentration effects in these strips:

Include Column Node Results

If the Finite Element Analysis Post-processing Form is used with this option selected, then the results obtained in the column nodes and wall end nodes will be returned for being taken into account during design.
This option is recommended for all slab strip types other than the "Fixed Band" strips.


Ignore Column Node Results

If the Finite Element Analysis Post-processing Menu is used with this option selected, then the results obtained in the column nodes and wall end nodes will be ignored and will not be taken into account during design.
This option can be used for "Fixed Band" strips. In this case, additional support steel may be necessary and can be inserted manually after design based on the maximum column node moments.


Average with Nearest Node Results

If the Finite Element Analysis Post-processing Form is used with this option selected, then the results obtained in the column nodes and wall end nodes will be ignored and will not be taken into account during design. Alternatively, values obtained by averaging the column node (or wall end node) with the first neighbour nodes around the column (or wall end). This way, the moment reduction effect of the finite column and wall dimensions will be taken into account in a better approach.

This option is recommended for the "Fixed Band" strips. In this case, additional support steel may be necessary and can be inserted manually after design based on the maximum column node moments.





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