How to Model and Analyze Structures Using ETABS
Prepared by: Yamen Ammar Dannan
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Steps for ETABS 2013
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Install ETABS 2013
Open ETABS
MAIN STEPS 1. New Model
Press (File -> New Model)
Choose the following settings
Design the (Grid Only) according to building plan of beams. (Spacing method). It is better to fill the uniform grid spacing, and then modify it with the custom grid.
Define story data (similar stories, heights). It is advised to fill in the simple story data, and then modify it using the Custom story.
Press Ok. The project is ready to start.
2. Define Materials “Steel and Concrete” from (Define -> Material Properties) Use default numbers (only change Strength of concrete(Fc’) if needed)
Note: (4000psi is the Concrete), and (A992fy50 is the Structural steel), and (A615Gr60 is the Rebar Steel).
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3. Define your Beams/Columns (Define -> Section property-> Frame Sections)
Press Add new Property…
Choose section shape
Name the section
Choose material (4000psi)
Define Dimensions
Press “Modify/Show Rebar” button -> If it’s a column, you can choose the reinforcement, and choose “to be checked”, or leave it as default and choose
Choose section type (Beam or Column)
FOR BEAMS (Special Purpose): Set Modifiers as shown
FOR COLUMNS (Special Purpose): Set Modifiers as shown
Repeat steps for as many beams/columns as required
4. Define your Slabs (Define -> Section property-> Slab Sections -> Add new Property)
Modeling type (Shell - Thin)
Type -> Slab and choose required thickness.
FOR SLABS (Special Purpose): Set Modifiers as shown
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5. Define your Walls (Define -> Section property-> Wall Sections -> Add new Property)
Modeling type (Shell - Thin)
Choose thickness.
FOR SHEAR WALLS (Special Purpose): Set Modifiers as shown
Make sure you select the correct type of adding, depending on modeling choice.
6. Realistic View: To get a visible view of the building components while drawing, go to (View -> Set display options -> check (Object fill + Extrusion)
7. Start drawing columns (Draw ->Draw Beam/Column/Brace -> Quick Draw Columns) then select the previously defined Column from the (Property Drop list).
And start placing them on the “Master story”. Or by dragging the cursor over all the nodes which have columns to be placed on them
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8. Draw the beams (Draw ->Draw Beam/Column/Brace -> Draw Beams/Columns/Braces) then select the previously defined beam sections from the (Property Drop list).
Start drawing the beams extending from corner to corner, depending on required design.
IMPORTANT NOTE: after you’re done drawing Columns and Beams, It is essential to release the moments at the end of continuous beams, to make them semirigid….Being Fully Rigid decreases the negative moment at the middle supports, which results in wrong design….
The Solution is to release the edge moments, and apply them as a point Moments. As shown in the following diagram.
which is done by selecting the continuous beams which have fixed ends, and going to (Assign -> Frame -> Release ->
Then select the end (Points) and go to (Assign -> Joint/Point Loads -> Force -> select LIVE -> Fill in MOMENT GLOBAL XX AND YY, with M =
.
Where “w” is the standard live load which you transfer on the beam as KN/m. (THIS MOMENT IS RELATIVELY SMALL, AND THIS STEP CAN BE PARTIALLY NEGLECTABLE IF YOU KNOW HOW MUCH EDGE REINFORCEMENT YOU SHOULD USE)
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1 Ref:(ACI-318-11, Section 8.3.3)
9. Draw the Slabs on the plan view (Draw -> Draw Floor/Wall objects -> Quick Draw Floor/Wall) then select the previously defined slab from the (Property Drop list). And start placing them on the “Master story”. And fill the openings with the “Opening” Property from drop list….. Or use the mouse dragging method to draw multiple Slabs on all Areas within the selection.
10. Draw the Shear walls on the plan view (Draw -> Draw Floor/Wall objects -> Quick Draw Walls) then select the previously defined wall from the (Property Drop list).
Don’t draw beams and columns; in the same places you draw shear walls. Overlapping causes wrong designs.
Further Modeling Notes:-
11. Meshing: An important Slab related modification is called “Meshing” which is breaking the slab into small segments, to get a more accurate analysis and for the finite element method to act correct. This is done by (Select -> Select -> by Object type -> Floors -> Select -> close) then (Edit -> Edit Shells -> Divide Shells -> change the numbers into 4 by 4 Areas.
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Assigning Loads on model
12. Define Loads: Go into (Define -> patterns)
Don’t change the dead and live load, (dead load will be automatically calculated by ETABS, and live will be assigned manually by us).
Add a new kind of load by writing into the empty box (Super) and Choose (Super Dead) from the drop list -> set weight multiplier to 0 -> press Add/new Load.
Add another kind of load called “Wall” with same options as “Super”.
Press Ok to close the window.
13. To add live load, check the local standard depending on the building purpose. And follow these steps:
(Select -> Select -> by Object type -> Floors ->Select -> close)
(Assign -> Shell Loads -> Uniform)
Load case: Live -> Load = from standard (ignore number is the picture) -> Direction: Gravity -> Ok.
14. To add wall load, calculate the wall load per meter, and apply it as follows:
Wall Load per meter = 1.7 Ton/m3 x 9.81 x Story height x Wall thickness = KN/m.
(Select the beams that have walls on them).
(Assign -> Frame loads -> Distributed)
Load case name : Wall -> Load = Wall Load per meter ( calculated, ignore number in picture)
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15. To add super imposed load, check the local standard depending on the building purpose. And follow these steps:
(Select -> Select -> by Object type -> Floors -> Select -> close)
(Assign -> Shell Loads -> Uniform)
Load case: SUPER
->
Load = from standard
->
Direction: Gravity ->
Ok.
16. To add wind load, follow the following steps:
IMPORTANT NOTE: Use “UBC-97” For wind and earthquake loads.
Go into (Define -> load patterns)
Add a new kind of load by writing into the empty box (WINDX) and Choose (WIND) from the drop list -> set weight multiplier to 0 -> press Add/new Load.
Press on the WINDX that was added into the list, and click “Modify Lateral Load” button
Keep the values default, and only change the Wind speed and exposure Type, according to your country standard, and press “OK”.
Add another new load by writing into the empty box (WINDY) and press Add/new Load.
Press on the WINDY that was added into the list, and click “Modify Lateral Load” button
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Only change the Angle from its default value to “90” and keep the rest as WINDX.
17. To add earthquake load, follow the following steps:
Go into (Define -> Patterns)
Add a new kind of load by writing into the empty box (EQX) and Choose (QUAKE) from the drop list -> set weight multiplier to 0 -> press Add/new Load.
Press on the EQX that was added into the list, and click “Modify Lateral Load” button.
Choose “X Dir + Eccen Y” and change the over strength factor according to the standard or simply use “4.5” for general cases. And Press “OK”.
Add a new kind of load by writing into the empty box (EQY) and Choose (QUAKE) from the drop list -> set weight multiplier to 0 -> press Add/new Load.
Press on the EQY that was added into the list, and click “Modify Lateral Load” button.
Choose “Y Dir + Eccen X” and change the over strength factor according to the standard or simply use “4.5” for general cases. And Press “OK”.
By The end of adding loads, you should have this.
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10 | P a g e Creating Load Combination
18. To add load combinations, preform the following steps:
Go to (Define -> Load Combinations)
Add a new combo.
Name the combo, and select Add.
Choose a case, and input the scale factor, and press add.
Choose another case, and input its scale factor, and press add.
Press Ok.
Repeat the steps by adding a new Combo, for as many combinations as required by standard.
You can use the auto generated load combinations from (Define -> Load Combinations -> Add default design combos -> choose according to model characteristics -> Press Ok)
Meshing the Shear walls
19. Meshing the shear walls is very important for a more realistic analysis, and effective design, it requires some effort to be done, but can be fairly easy using these steps:
(Select -> Select -> by Object Type -> Walls -> Select)
(View -> Show selected objects only)
Go to 3D view
Use the cursor and drag to select all the shear walls in the drawing
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(Edit -> Edit Shells -> Divide Shells -> change the numbers into 3 by 1 Areas.)
After meshing all the walls, go to 3D view; select all of the walls near each other, (walls that transfer loads to each other vertically), by dragging across them as shown in the picture
(Assign -> Shell -> Pier Label -> select P1 ->Apply -> Ok)
Repeat these steps for other wall collections required and assign them to new Piers as well (example P2, P3 …etc.)
Once done…(View -> Show all objects)
Assigning Diaphrams
20. Assigning Diaphram is a meant to make a single story rigid, to transfer lateral load through all of it sides, such as wind load or seismic load.
(View -> set 3D view -> Press xz -> (Aperture = 0)
Select the first floor from dragging the cursor from left to right, as shown.
(Assign -> Shell -> Diaphrams -> D1 -> ok)
Select the second floor similar to method used for first floor.
(Assign -> Shell/Area -> Diaphrams -> Modify show definitions -> Add New Diaphram-> Ok -> select the new created Diaphram -> then Ok)
Repeat for desired number of stories.
When you have two or more separate structures, with some floors separated. Make sure you do the assign floors as different Diaphrams
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Correct Diaphram
Wrong Diaphram
Offsetting and Rigidity Modifications
21. When drawing beams/columns/walls/slabs they are drawn from center line to center line, which makes an overlap whenever two sections are joined. To fix this we apply the following:
(Select -> Select -> All)
(Assign -> Frame -> End (Length) offsets.)
Leave the default setup as it is
Press Ok
22. In real life, the beams and columns aren’t 100% fixed; they have a limited degree of flexibility which ETABS doesn’t consider unless we change the following.
(Select -> by Line object type -> Beam -> Ok.)
(Assign -> Frame -> End (Length) offsets.)
Change the Rigid Zone Factor to (0.5).
Press Ok
Auto line constraint
23. It is essential to merge the mesh lines in order to transfer loads equally in a realistic way, therefore this step should be done in the end before the start of any analysis.
(Select -> Select -> All)
(Assign -> Shell/Area -> Auto Line constraint)
Leave the default setup as it is
Press Ok
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13 | P a g e Sequential construction
24. In real life, construction of the building is done on steps, usually (floor by floor), so the appliance of load isn’t sudden, to simulate such real life case, we add a sequential construction case by:
(Define -> Auto Construction Sequence case)
Check the “Replace Dead Type Load cases with this load case…….” As True.
Press Ok.
The Analysis
25. Once done of the all the steps, you can start running the analysis.
(Analyze -> Run Analysis)
This may take several seconds to minutes.
(Design -> Concrete Frame Design -> Start Design/Check)
(Design -> Shear Wall Design -> Start Design/Check)
(Detailing -> Start Detailing)
Once done, you can show the following results:o
Show deformed shape due to any load case or combination you choose
o
Right click any beam in the model, to view, Shear/Moment diagrams. And observe the maximum values, and design for them.
o
Show result tables, and generate a report of them.
o
Display ratio of steel required in each reinforced beams, shear walls, and columns
o
Display suggested sections for steel beams.
o
Display maximum deformations.
o
Display Slabs Stress diagrams as a contour sketch.
o
Display detailed shear wall reinforcement and rebar spacing.
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14 | P a g e
Steps for ETABS 9.7.4
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15 | P a g e
Install ETABS 9.7.4
Open ETABS
MAIN STEPS 26. New Model
New model initialization (Press No)
Choose project units (KN/m)
Design the (Grid Only) according to building plan of beams. (Spacing method). It is better to fill the uniform grid spacing, and then modify it with the custom grid.
Define story data (similar stories, heights). It is advised to fill in the simple story data, and then modify it using the Custom story.
Press Ok. The project is ready to start.
27. Define steel standard (Options -> Preferences -> Steel Frame design) (local standard = BS 5950)
28. Define Concrete standard (Options -> Preferences -> Concrete Frame design) (local standard = ACI-318)
29. Define Shear wall standard (Options -> Preferences -> Shear wall design) (local standard = ACI-318)
30. Choose Rebars sizes available in market: (Options -> Preferences -> Reinforcement bar sizes -> delete what’s not available in country)
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31. Define Materials “Steel and Concrete” from (Define -> Material Properties) Use default numbers (only change Strength of concrete(Fc’))
32. Define your Beams/Columns (Define -> Frame sections -> click to-> Add/Wide flange > Add Rectangular)
Name the section
Choose material (Concrete or Steel)
Define Dimensions
Press Reinforcement button -> If it’s a column, you can choose the reinforcement, and choose “to be checked”, or leave it as default and choose
FOR BEAMS (Special Purpose): Set Modifiers as shown
FOR COLUMNS (Special Purpose): Set Modifiers as shown
Repeat steps for as many beams/columns as required
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33. Define your Walls and Slabs (Define -> Wall/Slab/Deck -> Modify the default walls and slabs to your design requirements)
(Note: choose “Shell” while modifying a Wall/Slab)
FOR SLABS (Special Purpose): Set Modifiers as shown
FOR SHEAR WALLS (Special Purpose): Set Modifiers as shown
Now that we’re done defining sections to be used. Make sure before you start modeling, that you select the correct type of adding, depending on modeling choice.
34. Realistic View: To get a visible view of the building components while drawing, go to (View -> Set building view options -> check (Object fill + Extrusion).
35. Start drawing columns (Draw ->Draw lines object -> Create Columns) then select the previously defined Column from the (Property Drop list). And start placing them on the “Master story”. Or by dragging the cursor over all the nodes which have columns to be placed on them
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36. Draw the beams (Draw ->Draw lines object -> Draw lines) then select the previously defined beam sections from the (Property Drop list). And start placing them on the “Master story”… Or use the mouse dragging method to draw multiple beams on all lines within the selection.
IMPORTANT NOTE: After you’re done drawing Columns and Beams, It is essential to release the moments at the end of continuous beams, to make them semirigid….Being Fully Rigid decreases the negative moment at the middle supports, which results in wrong design….
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19 | P a g e
The Solution is to release the edge moments, and apply them as a point Moments. As shown in the following diagram.
which is done by selecting the continuous beams which have fixed ends, and going to (Assign -> Frame/Line -> Frame Release ->
Then select the end (Points) and go to (Assign -> Joint/Point Loads -> Force -> select LIVE -> Fill in MOMENT GLOBAL XX AND YY, with M =
or
Where “w” is the standard live load which you transfer on the beam as KN/m. (THIS MOMENT IS RELATIVELY SMALL, AND THIS STEP CAN BE PARTIALLY NEGLECTABLE IF YOU KNOW HOW MUCH EDGE REINFORCEMENT YOU SHOULD USE)
2Ref:(ACI-318-11, Section 8.3.3)
37. Draw the Slabs on the plan view (Draw -> Draw Area objects -> Create Areas at Click) then select the previously defined slab from the (Property Drop list). And start placing them on the “Master story”. And fill the openings with the “Opening” Property from drop list….. Or use the mouse dragging method to draw multiple Slabs on all Areas within the selection.
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20 | P a g e
38. Draw the Shear walls on the plan view (Draw -> Draw Area objects -> Draw walls) then select the previously defined wall from the (Property Drop list).
Don’t draw beams and columns; in the same places you draw shear walls. Overlapping causes wrong designs.
Further Modeling Notes:-
39. Meshing: An important Slab related modification is called “Meshing” which is breaking the slab into small segments, to get a more accurate analysis and for the finite element method to act correct. This is done by (Select -> by Wall/Slab -> *name of Slab*) then (Edit -> Mesh Area -> change the numbers into 4 by 4 Areas.
Assigning Loads on model
40. Define Loads: Go into (Define -> Static load cases)
Don’t change the dead and live load, (dead load will be automatically calculated by ETABS, and live will be assigned manually by us).
Add a new kind of load by writing into the empty box (Super) and Choose (Super Dead) from the drop list -> set weight multiplier to 0 -> press Add/new Load.
Add another kind of load called “Wall” with same options as “Super”.
41. To add live load, check the local standard depending on the building purpose. And follow these steps:
(Select -> by Wall/Slab -> *name of Slab*)
(Assign -> Shell/Area Loads -> Uniform)
Load case: Live -> Load = from standard (ignore number is the picture) -> Direction: Gravity -> Ok.
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21 | P a g e
42. To add wall load, calculate the wall load per meter, and apply it as follows:
Wall Load per meter = 1.7 Ton/m3 x 9.81 x Story height x Wall thickness = KN/m.
(Select the beams that have walls on them).
(Assign -> Frame/Line loads -> Distributed)
Load case name : Wall -> Load = Wall Load per meter ( calculated, ignore number in picture)
43. To add super imposed load, check the local standard depending on the building purpose. And follow these steps:
(Select -> by Wall/Slab -> *name of Slab*)
(Assign -> Shell/Area Loads -> Uniform)
Load case: SUPER -> Load = from standard -> Direction: Gravity -> Ok.
44. To add wind load, follow the following steps:
IMPORTANT NOTE: Use “UBC-97” For wind and earthquake loads.
Go into (Define -> Static load cases)
Add a new kind of load by writing into the empty box (WINDX) and Choose (WIND) from the drop list -> set weight multiplier to 0 -> press Add/new Load.
Press on the WINDX that was added into the list, and click “Modify Lateral Load” button
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22 | P a g e
Keep the values default, and only change the Wind speed and exposure Type, according to your country standard, and press “OK”.
Add another new load by writing into the empty box (WINDY) and press Add/new Load.
Press on the WINDY that was added into the list, and click “Show Lateral Load” button
Only change the Angle from its default value to “90”.
45. To add earthquake load, follow the following steps:
Go into (Define -> Static load cases)
Add a new kind of load by writing into the empty box (EQX) and Choose (QUAKE) from the drop list -> set weight multiplier to 0 -> press Add/new Load.
Press on the EQX that was added into the list, and click “Show Lateral Load” button.
Choose “X Dir + Eccen Y” and change the over strength factor according to the standard or simply use “4.5” for general cases. And Press “OK”.
Add a new kind of load by writing into the empty box (EQY) and Choose (QUAKE) from the drop list -> set weight multiplier to 0 -> press Add/new Load.
Press on the EQY that was added into the list, and click “Show Lateral Load” button.
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Choose “Y Dir + Eccen X” and change the over strength factor according to the standard or simply use “4.5” for general cases. And Press “OK”.
By The end of adding loads, you should have this.
Creating Load Combination
46. To add load combinations, preform the following steps:
Go to (Define -> Load Combinations)
Add a new combo.
Name the combo, and select Add.
Choose a case, and input the scale factor, and press add.
Choose another case, and input its scale factor, and press add.
Press Ok.
Repeat the steps by adding a new Combo, for as many combinations as required by standard.
You can use the auto generated load combinations from (Define -> Add default design combos -> choose according to model characteristics -> Press Ok)
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24 | P a g e Meshing the Shear walls
47. Meshing the shear walls is very important for a more realistic analysis, and effective design, it requires some effort to be done, but can be fairly easy using these steps:
(Select -> by Wall -> *name of wall*)
(View -> Show selection only)
Go to 3D view
Use the cursor and drag to select all the shear walls in the drawing
(Edit -> Mesh Area -> 3 by 1 -> ok)
After meshing all the walls, go to 3D view; select all of the walls near each other, (walls that transfer loads to each other vertically), by dragging across them.
(Assign -> Shell/Area -> Pier Label -> Type name -> Press Add New Name -> Press Ok)
Select other wall collections required and assign them to new Piers as well.
Once done…(View -> Show all)
Assigning Diaphrams
48. Assigning Diaphram is a meant to make a single story rigid, to transfer lateral load through all of it sides, such as wind load or seismic load.
(View -> set 3D view -> Press xz -> (Aperture = 0)
Select the first floor from dragging the cursor from left to right, as shown.
(Assign -> Shell/Area -> Diaphrams -> D1 -> ok)
Select the second floor similar to method used for first floor.
(Assign -> Shell/Area -> Diaphrams -> Add/New -> Ok)
Repeat for desired number of stories.
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25 | P a g e
When you have two or more separate structures, with some floors separated. Make sure you do the assign floors as different Diaphrams
Correct Diaphram
Wrong Diaphram
Offsetting and Rigidity Modifications
49. When drawing beams/columns/walls/slabs they are drawn from center line to center line, which makes an overlap whenever two sections are joined. To fix this we apply the following:
(Select -> All)
(Assign -> Frame/Line -> End (Length) offsets.
Leave the default setup as it is
Press Ok
50. In real life, the beams and columns aren’t 100% fixed; they have a limited degree of flexibility which ETABS doesn’t consider unless we change the following.
(Select -> by Line object type -> Beam -> Ok.)
(Assign -> Frame/Line -> End (Length) offsets.
Change the Rigid Zone Factor to (0.5).
Press Ok
Auto line constraint
51. It is essential to merge the mesh lines in order to transfer loads equally in a realistic way, therefore this step should be done in the end before the start of any analysis.
(Select -> All)
(Assign -> Shell/Area -> Auto Line constraint)
Leave the default setup as it is -> Press Ok
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26 | P a g e Sequential construction
52. In real life, construction of the building is done on steps, usually (floor by floor), so the appliance of load isn’t sudden, to simulate such real life case, we add a sequential construction case by:
(Define -> Add sequential construction case)
Keep options default unless advised.
Press Ok.
(This has to be run separately after running the normal analysis, by going to (“Analyze -> Run sequential construction analysis).
The Analysis
53. Once done of the all the steps, you can start running the analysis.
(Analyze -> Run Analysis)
This may take several seconds to minutes.
(Design -> Concrete Frame Design -> Start Design/Check)
(Design -> Shear Wall Design -> Start Design/Check)
Once done, you can show the follow results:o
Show deformed shape due to any load case you choose
o
Right click any beam in the model, to view, Shear/Moment diagrams. And observe the maximum values, and design for them.
o
Show result tables, and generate a report of them.
o
Display ratio of steel required in each reinforced beams, shear walls, and columns
o
Display suggested sections for steel beams.
o
Display maximum deformations.
o
Display Slabs Stress diagrams as a contour sketch.
o
Display detailed shear wall reinforcement and rebar spacing.
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For more questions
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27 | P a g e
The End o This guide contains both steps for version 9.7.4 and 2013. o The guide only serves as an introduction, and more effort should be considered to master such complicated software. o Always comply with your region/country standards, and ignore numbers provided in the tutorial when they differ from the advised values. o This guide isn’t a bible, so feel free to ask or disagree with the author. o ETABS can be best learned through:
Trial and Error
Video tutorials
Books
o Main reference used:- (Eng. Makar Nageh, 2007, How to model and design high rise buildings using ETABS) “The book is available with the author of this guide as a PDF in case you need it” o Obtaining the ETABS software is your responsibility, and illegal distribution isn’t encouraged by any means. o The author is a civil engineering student, and isn’t a certified trainer, but holds a certificate from the UAE Society of engineers, to design using ETABS. o Feel free to contact the author “Yamen Dannan” for any inquiries related to the software. at (
[email protected])
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