Background 

With FE Floor Analysis, you can analyze and design floors under vertical loads only independently from the global 3D building analysis. 

In this approach, the floor is isolated from the building and only gravity and imposed loads are applied. This allows engineers to simulate design scenarios where vertical loads govern.

When conduct a “FE Chase-down” analysis, where it analyze the floors (under vertical loads only) from top to bottom, iteratively applying the calculated column reactions onto the floor below. This methodology is preferred by some engineers, who would like to eliminate the 3D side effects of a global 3D FE Analysis such as the 3D frame effects and differential settlements due to relative axial rigidities. This method simulates the good old 2D hand calculation methods in a 3D environment.

For general guidance on different analysis methods, refer to :  Modelling, Analysis & Design Flowchart

There are two ways that you can run FE Floor Analysis : 

1.   Run FE Floor Analysis for selected floors only 

1. In this case, you can get meaningful results slabs using FE mesh - which can then be used to design slab using Finite element method
   
2. For further guidance, you can refer to : Slab Analysis and Design Procedure

2.  Run FE Floor Analysis Gravity Load Chasedown 

1. In this case, you need to run FE Floor Analysis of all stroreys starting from the top to bottom storey.
   
2. In addition to slab analysis results, this will also provide you with meaningful beams, columns and walls forces, due to gravity load cases. 
   
3. Once completed, you have to option to use method to design the beams, columns and walls, instead of default Building Analysis method. 
   
4. You may find this article helpful : Difference between Building Analysis and FE Floor Analysis

Perform Finite Elements (FE) Floor Analysis

Go to Analysis ribbon and pick "FE Floor analysis" (as shown below).

The FE Floor Analysis dialog will be launched : 

1. Select one or more than one floor and click "Floor Mesh and Analysis" to run FE Floor Analysis. All selected floors will be meshed and analysed at once.

1. Click “Select/Deselect All” to select all storeys or de-select all storeys.
   

1. An automated calculation is provided for this purpose; read Cracking & Creep Factor Calculator. 
   

1. A single node will be used for modelling the columns if this option is not checked, i.e. slabs will be meshed to column insertion node.  
2. The FE Analytical Model for column, beam and slab joint, with this option unchecked, is shown below : 
   

1. If this option is checked, rigid links are provided to create a rigid column outline, resulting in slab being meshed to the outline of column. 
   
2. The FE Analytical Model for column, beam and slab joint, with this option checked, is shown below (rigid links in dark blue) : 

1. This option is very useful for reducing the support moments at column nodes by considering the section of the column.
   
2. However, the analysis is more complex if this option is checked as rigid links must be created to the column outline.  As such, is there are meshing errors, try unchecking this option. 

This option applied only for columns with connected beams, i.e. beam slab systems. 

For flat slab system, i.e. column supporting slab directly (with no beams), this option will automatically be considered, i.e column outlines will always be considered.

ALL storeys must be selected and this option must be checked in order to perform chase-down analysis. This will ensure the result can merged correctly in later stage. For more details about merging result of beam/column, please refer to What is Merge FE Column/Beam result with Example

The key objective is to choose an ideal balance of Plate Element Size to produce minimum number of plates but still sufficient to an accurately replicate the "true" behavior of the slab (so analysis time is minimized). Generally, try to achieve 6 to 8 plates between the column heads. 

Post Analysis Processes and Report

1. Storey will be highlighted as green color when FE Floor Analysis is completed.
   
1. If “FE Chase-down” is performed, “▼” will be displayed next to the storey. Otherwise, it will be greyed.
   
2. After FE Floor Analysis is done, clicking "Display Analytical Model" will open "FE Floor Model" to view the visualized result for selected storey. See below under topic : FE Floor Model.
3. Other than the visualized result, FE Floor Analysis result can be viewed and generated in text form after completion of the analysis without any errors. 
   
1. The analysis result reports can be prepared for selected nodes, slabs, and/or frame members. 
   
2. In all tab pages, you select items to be included using the visible lists and then press the “Create Report” button to generate the report.
   
4. To examine the minimum and maximum of displacement, click “List Maximum Storey Displacement”.
5. After FE Chase-down is done, you will be able to merge column and/or beam result with Building Analysis result.  Please read :  What is Merge FE Column/Beam result with Example
6. After merged the result and close & reopen the dialog, "Axial Load Comparison Report" will provides a means of verifying the total dead load and live load applied to the building. It also can be used to cross-check:
1. slab loads have been correctly decomposed onto the supporting members. 
2. gravity load applied matches the Building Analysis total vertical reaction. 
3. gravity load applied matches the FE Chase-down total vertical reaction.
7. For FE Floor Analysis models, it should be noted that they don't include for the effects of pattern loading.
   
1. It is not feasible to automate pattern loading to generate every possible worst case scenario for every conceivable irregular arrangement.
   
2. If it is a concern in your design, it is suggested that amplifying the "Positive Moment Factor" (10 to 20%, i.e. 1.1 to 1.2) to allow for these effects.
   
3. Output results that viewed in "FE Floor Models" view is factored using the values entered in these fields. 
   

These factors should be defined before clicking "Display Analytical Model" in dialog. 

FE Floor Model 

1. Storeys list acts as "Storey Selector" which allows you switch the result of floors by click the relevant storey on the list.
   
1. A right arrows ">>>" symbol indicates the current selected floor.
   
2. A check sign ""means a valid FE Analysis exists for that floor while a cross sign "X" means that an  FE Analysis has been performed but it is not valid anymore.
   
3. If an FE Analysis has not been performed for a specific floor, it will still be listed however it won't accessible. 
   
2. FE Floor Analysis is performing sub-frame analysis under vertical load cases/combinations only, hence only vertical load cases/combinations will be listed in FE Floor Analysis Post-processing model. Results will be displayed for selected load case or combination.
3. "Effect" panel will appear when "Contour" is toggled on in Contour tab. 

Effects Panel

1. Displacement: Displacement of the nodes along global direction. 
2. F11: Horizontal Axial Force per unit length
3. F22: Vertical Axial Force per unit length
4. F12: Shear Force per unit length
   
5. V13: Out of plane shear force at face 1 acting towards local axis 3
   
6. V23: Out of plane shear force at face 2 acting towards local axis 3
7. M1: Moment about Direction-1 per unit length** (Local)
8. M2: Moment about Direction-2 per unit length** (Local)
9. M12: Twisting Moment per unit length
10. M1d-bot: Design Moment about Direction-2 at bottom (allows Wood-Armer Adjustment)
11. M2d-bot: Design Moment about the Direction-1 at bottom (allows Wood-Armer Adjustment)
12. M1d-top: Design Moment about Direction-2 at top (allows Wood-Armer Adjustment)
13. M2d-top:  Design Moment about the Direction-1 at top (allows Wood-Armer Adjustment)
14. As1-bot (local): Required steel area in the bottom face of the slab in Direction-1
15. As2-bot (local): Required steel area in the bottom face of the slab in Direction-2
16. As1-top (local): Required steel area in the top face of the slab in Direction-1
17. As2-top (local): Required steel area in the top face of the slab in Direction-2
18. Asd1-bot (Wood-Armer): Required steel area in the bottom face of the slab in Direction-1 (Wood-Armer Effects included) 
19. Asd2-bot (Wood-Armer): Required steel area in the bottom face of the slab in Direction-2 (Wood-Armer Effects included) 
20. Asd1-top (Wood-Armer): Required steel area in the top face of the slab in Direction-1 (Wood-Armer Effects included) 
21. Asd2-top (Wood-Armer): Required steel area in the top face of the slab in Direction-2 (Wood-Armer Effects included) 
22. Soil Pressure: The soil pressure applied on the node (only shown if ST00 is active & FE Foundation Analysis done)
23. Soil Pr. Threshold: The threshold plot of the soil pressure against the allowable soil stress value  (only shown if ST00 is active & FE Foundation Analysis is done)

Wood-Armer Effects 

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. 

Contours

Contours

If "Line Contours"  is toggled on individually, the contour line color will be shown in Black color. If it is toggled on together with " Colored Lines" , the contour lines colors will follow the contour colors itself. 

User Defined Contour

1. The "Effect" and "Loading" that selected for user defined contour. 
2. Click the "Update" button to update the intervals value according to contour count. 
3. Contour interval values will automatic generated by program based on the result and contour count. 
4. Contour Legend format that going to use in user defined contour. 
5. Input or/and select the options and click "Update" to update the interval value & label of contours. 
6. Click "Redraw" to regenerate/update the user defined contour. 

Threshold Contours

Icons ,  ,   allow you to switch on / off contours of these shell element

Display

The display icons affects the display settings. 

Transparency 

Setting to adjust transparency of the contours. 

Sync to Legend 

If "Sync to Legend" is unchecked, then "Quantity" below is enabled and you can choose how many gradation of colors to display the contour. 

If "Sync to Legend" is checked, then contours colors will match exactly with the legend.  Example, if the legend shows 5 colors, the shell contours will also show the same 5 colors. 

Show Min As in Rebar Contours (Minimum required steel area)

If this option is checked, the minimum rebar area will be calculated for each node using the selected design code formulations and the associated shell thickness. If the required rebar area is greater than the minimum, then the required rebar area will be plotted.

Otherwise, the minimum rebar area will be used for that node. This means that, if the required rebar area is smaller than the minimum for all nodes, you will see all the shells colored with a single color.

The above picture shows Top Rebar Required Area in local axis direction 2 when Show Min. As in Rebar Contours option is unchecked.Note that the maximum value is 6.25 cm2/m and minimum value is zero. The minimum value is zero because the contours are showing only the top bars. Positive moment regions are shown with zero value. 

In the picture above, the Show Min. As in Rebar Contours option is checked. Note that the minimum value in the legend is 4.03 cm2/m which is the code minimum value for the slab. The required area below the minimum value is suppressed and shown by a blue color (the color for minimum). The required rebar area values above the minimum value are colored according to the legend.

Legends

When Legend button is toggled on, a legend will be displayed at the screen. “ Index Count” can be adjusted to shows the interval value based on the contours. Position and size of the legend can easily be controlled by “ Position” and “ Size” fields in legend panel.

Details

Properties 

Detailed Contours 

Slab Strip Diagram

1. If Building Analysis is adopted in model, ensure that floors are meshed in Building Analysis. 
2. After analysis is done, select the FE Slab strip object in model view.  
3. Right-click and select "Strip Profile"
4. Alternatively, slab strip diagram also can be generated through the same menu button on the slab strip contextual ribbon tab tat appears when the slab strip is selected.  

      

1. Open Analytical Model for FE Floor Model or Building Analysis
2. Go to Result tab, select slab strip you want to review from the Slab Strip List. This will display the moment diagrams of selected strip on the analytical view
3. To view the detailed profile, select a slab strip on the analytical model, right-click > select "Slab Strip Diagram Profile"

You may find these related article helpful : 

1. Working with Flat Slabs
   
2. Slab Analysis and Design Procedure