Defining a New Slab

Before inserting a Slab member its reference axes should be defined.

To define a new Slab member:

1. Display the storey level in the drawing area which will contain the slab.
   
2. Press the “Slab” button located in "Modelling" ribbon.
   
3. Slab "Properties” dialog will appear 
   
1. If load cases and combinations has not been defined, there will be a prompt to generate them.
   
4. Edit the fields in the "Slab Properties" form. For example, enter the Slab Label in the "Label" field (max. 11 characters) and modify the slab thickness "h".
   
5. Press the “Loads” tab in the “Slab Properties” form to access the next page and define the dead and imposed loads of the slab. 
   
6. In either the plan or 3D view, pick the position of the slab.
   
1. By default, "Beam Region" is set as the insertion method. So, picking a closed region surrounded by beams and/or walls will be sufficient to define the slab boundaries. For the other insertion methods see related topics further in this section.
   
7. Edges of the slab will be numbered in counter-clockwise direction and displayed in Graphic Editor, as first edge being the lower edge on plan.
   

Editing an Existing Slab

In order to edit an existing slab:

1. Select the slab.
   
2. Right-click and select “Properties”. (“Properties” can be accessed alternatively by pressing the “Slab” button).
   
3. Modify the fields such as "Label", "h" and/or loadings in the "Slab Properties" form.
   
4. Press the "Update" button in the form.
   

You can repeat this process with as many members as you wish. One member at a time can be edited by this method. In order to update several slabs at once, you can use the "Slab Table" via right-click menu.

Insert Slabs Automatically

Multiple slabs can be automatically inserted adjacent to selected beams.

To insert slabs automatically:

1. Multiple select any beams at the boundary of intended slabs.
   
2. Click on Slab Properties icon & input the required data. 
   
3. Click on  Insert Slabs Automatically   in "Modelling" ribbon . 
   

Setting Slab Types Automatically

Slab types are used by the analytical analysis procedures. You can use “Set Slab Types Automatically” form to assign the slab types considering the neighbour panels in the plan.

In order to initiate this function,

1. Right click to the “Slabs” node in the “Structure Tree” and select "Set Slab Types Automatically " menu option. In this case, the function will be applied to all slab panels in the model.
   
2. Select one or more slabs and load the short-cut menu using the right mouse button and select “Set Slab Types Automatically” option. In this case, the function will be applied to selected slab panels (or all slab panels if “Determine the Types of All Slabs in the Storey” is checked).
   

The slab types will be assigned when the “OK” button is pressed.

This option cannot determine the types of cantilever slabs and slab panels with more than 4 edges.

Slab Table

You can use the "Slab Table" in the right-click menu to modify one or more existing slabs. All cells in the table are editable. You can use the cursor keys or mouse cursor to select a cell and edit the contents.

The "Search" button can be used to find a specific member after typing the label to the "Member" field.

You can close this dialog window using “Close” button. All the changes made in this window will be applied immediately. 

Slab Load Decomposition

ProtaStructure transfers the loads from slabs automatically using the yield line theory. Optionally, FE slab load decomposition can be applied.

Beam loads may be viewed, edited or printed at any time selecting a beam and using the "Edit Member Loads" option in the shortcut menu accessed by right clicking the mouse

Slab Properties

" Slab Properties " will be loaded when the " Slab " option in the "Modelling" ribbon is selected. A new slab can be defined by arranging the fields in the form and then by clicking on one or more regions surrounded by axis elements in the plan window.

The “Slab Properties” form can also be accessed after selecting an existing slab and then by right-clicking and choosing the “Properties” option in the shortcut menu. You can select a slab member by using one of the “Member Selection” methods described previously.

When the “Slab Properties” form is open, right clicking a new slab member and selecting the “Select and Load Properties” option in the shortcut menu will load the properties of the new member in the same window.

The "Slab Properties " form has two tab pages named “General” and “Loads”. You can shift between the pages by pressing the related tab heading.

The General tab comprises the following fields:

Slab Label

Slab Type

The boundary conditions of the slab are determined from its entry. "Slab Type" codes are used for the design of uniform slabs using the moment coefficients method.

Available Slab Panel Types

A button menu that contains all the possible types will appear when this field is clicked. You should make a selection from the menu according to the boundary conditions of the slab.

Slab Types 12 is reserved for the "Cantilever Slabs”. This is used by the Finite Element Slab Strips as well. For normal slabs, any other slab type selection (i.e. All Edges Continuous) can be selected.

The  slab type in the list is used for modelling the one-way slabs. Prefabricated slabs whose two parallel edges do not transfer load to the system, can be classified in this category.

The hatched edge in the panel types define as the slab continuity at the edge (Not beam).

Slab Thickness (h)

You can enter the thickness of the slab ("h") in this field. The slab thickness value will appear in the plan window. If the thickness of the slab is smaller than the minimum slab thickness required, the program will sound an alarm and a warning note will appear in the status bar.

Relative Level

In order to define the relative top level of the slab you can use this field. According to the negative or positive values you entered, the slab will be lowered or raised from default top storey level.  By this way, you can define slab systems with different elevations.  

Apply Z to Analytical Model

Concrete Cover

This field can be used to specify the nominal concrete cover measured from the bar face to the edge of the slab. The effective depth of the slab is calculated using this concrete cover, the size of the bars used and the layer number of the tension reinforcement.

A global control of nominal concrete covers can be achieved by going to  tab "Building Setout" > "Settings Center" > "Slab" > "Design" > "Parameters".

Label Position

Slab label will be placed at the center of slab by default. Slab label position will shows in differently location based on the button. Red circle in the button represents the label position.

Angle

Primary reinforcement direction angle of the slab can be defined using the “Angle” field. The “M1” moment contours and “M1d” design moment contours of the slab will be generated along this direction in Finite Elements Floor Model Post-processor Window. The “M2” and “M2d” contours will be generated along perpendicular to the direction defined by this global angle.

Note that “Mx” and “My” moment contours are generated along global x and y directions respectively.

The direction defined by the “Angle” field is measured in degrees counter-clockwise with positive x-axis to be “0”.

Slab Insertion Methods

A standard slab can be inserted in a region bounded by beams or by axes. The selection of slab insertion methods can be accessed by clicking the dropdown button.

Note that, these methods are not applicable for the insertion of cantilever slabs.

Axis Region

Beam Region (Default)

Pick Axis

Pick Points

In the case of an error while using this method, all previously defined axes can be deleted by pressing the “Delete All Axes” button then you can restart the definition of the slab.

Pick Closed Slab Edge

Loads tab

Self Weight

The Self-weight (per area) of the slab will be calculated automatically using the "Unit Weight of concrete" defined in "Materials" section and "Slab Thickness".

The calculated value cannot be manually edited. In order to neglect the self weights of the members you have to set "Unit Weight of concrete" defined in "Project Parameters" section to zero. Alternatively, a negligible (very small) "Self Weight" value may be entered in this field.

Dead Load (Additional)

The calculated weight (per area) in the above field does not include any additional covers. To add additional weights such as ceiling plaster, fake ceiling, floor finishes, the "Dead Load" field under "Loads" tab can be used.

Imposed / Live Load

The imposed live loads (per area) on the slab can be defined using this field. Right-clicking on this field will provide access to standard imposed loads defined in the codes.

Slab Does Not Contribute To Floor Diaphragm

Usually in the analysis of the building systems, slabs are considered to behave infinitely rigid in their planes, thus, forming rigid diaphragm action.

If “Slab Does Not Contribute to Floor Diaphragm” is checked, that slab will not participate in rigid diaphragm action. By this way, all the nodes linked to the corners of this slab will displace independent of rigid diaphragm.

Subgrade Co-efficient (Foundation Level slabs only)

Creating of Rectangular Cantilever Slab

1. Click on Slab icon & choose Type = 12. 
   
2. Go to cantilever tab, input values, example cantilever length accordingly. 
   
3. Pick first intersection of axis to define start of cantilever slab (i.e. "I" node of supporting beam)
   
4. Pick second point to defined end of cantilever slab (i.e. "J" node of supporting beam) 
   
5. Move cursor to the side where it is to be inserted (a grey preview will be shown)
   
6. Pick third point to confirm and insert the cantilever slab. 
   

Cantilever tab 

Cantilever Sab Dimension "d" , "b-Slab", "L-Cant" 

1. "d" is the distance from the reference point to the beginning of the slab. The reference point of the slab is always the first point picked during the insertion of the cantilever slab.
   
2. b-Slab" is the width measured along the supported edge.  If "b-Slab" = 0 then the slab is defined as spanning completely between the insertion points.
   
3. "L-Cant" is the cantilever length. 
   

Creating Irregular Cantilever Slab

1. Click "Polyline Slab / Column Edge" icon in "Modelling" ribbon
   
2. Pick a point to define start of cantilever slab. Click continuously to define the edge of the cantilever slab. The method to draw the slab edge lines are similar to multi-segment axis.
   
3. At the last point, right-click and select "Finish" to end the insertion and the slab edge lines will be drawn.
   
4. Click on the Slab icon. In the Insertion Option, ensure that Beam Region is selected.
   
5. Ensure the selection of slab type is "Type = 1".
   
6. Click anywhere within the slab edge line and a new slab will be created.