Etabs Tutorial MSc Nguyen Thanh Tu
Example 5
Using Etabs to determine natural frequencies, mode shapes and the internal forces of the
building with plans as follow? The building has 15 floors and a basement. The depth of the
top of foundation is 1.5 m. The height of the basement is 3m, the bottom height is 4m, the
others are 3.3m, the height of all slabs is 120 mm, the width of the concrete wall is 300mm.
The main beams are reinforcement concrete with 300x600 mm; secondary beams are
250x400 mm; columns are 600x600 mm. Concrete: B20: E = 2,7e7 Pa, =0.2. Loads are:
- Dead loads (DL) include: self-weight, wall loads and super dead load.
o Super dead load: Super dead loads are basically superimposed dead loads which
are applied on a structure. So e.g. self-weight of the slab is dead load while the
loads of any finished, partitioning, cladding, false ceiling are all super dead loads
Thickness Weight per unit Overload Calculate load
No. Layers of floor 3
(mm) (kN/m ) factor (kN/m2)
1 Tiles 10 18 1.2
2 Flooring mortar 20 20 1.2
3 Ceiling mortar 15 20 1.2
Ceiling, technical
4 0.5 1.1
pipeline
Sum kN/m2
o Wall loads: assume that wall (bwall= 100mm) will be built on all the beams
Calculate wall loads:
Basement: Main beams: WL100 = (kN/m).
Secondary beams: WL100 = (kN/m)
4m story: Main beams: WL100 = (kN/m).
Secondary beams: WL100 = (kN/m)
3.3m story: Main beams: WL100 = (kN/m).
Secondary beams: WL100 = (kN/m)
- Live loads (LL): calculated uniform load on all slabs is 2.4 kN/m2.
o Calculate uniform Live loads in houses: 2×1.2 = 2.4 kN/m2.
o Calculate uniform Live loads in corridors: 2×1.2 = 2.4 kN/m2.
o Calculate uniform Live loads in the terrace: 0.75×1.2 = 0.9 kN/m2.
- Wind Loads (WL) The building will be constructed in II-A area.
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Tutorials
I. DEFINE MODEL
1.1. Open Etabs program.
1.2. Change Unit.
Choose kN-m
1.3. New Model Initialization.
Menu File > New Model
Choose “NO”
Edit the gird of model Edit the story height of model
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Set Elevation view: Menu View → Set Elevation or click:
Note: remember to Save file regularly. Each model should be in a folder.
Edit girds: Menu Edit→ Edit Grid Data→ Edit Gird or right-click on screen and
choose Edit Grid Data
Edit story height: Menu Edit→ Edit Story Data→ Edit Story or right-click on screen
and choose Edit Story Data.
Insert or delete story: Menu Edit→ Edit Story Data→ Edit Story, choose Insert Story or
Delete Story
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1.4. Define parameter
a. Define material
Menu Define > Material Properties or click
b. Define frame section.
Menu Define > Frame Sections or click
Note : Beam : Bbxh
Column : Cx×y
T3:
T2 :
c. Define wall/ slab/ Desk Sections (*)
Define slab: Menu Define > Wall/Slab/Deck Sections
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Define wall: Menu Define > Wall/Slab/Deck Sections
d. Define Static Load Cases
Menu Define > Static Load Cases or click:
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e. Define Load Combinations
Menu Define > Load Combinations or click
No Load Combination Load combination Case Name Scale factor
Name Type
1 DL Add SW; WL; SDL 1;1;1
2 Comb1 Add DL; LL 1;1
3 Comb2 Add DL; WX 1;1
4 Comb3 Add DL; WX 1;1
5 Comb4 Add DL; WY 1;1
6 Comb5 Add DL; WY 1;1
7 Comb6 Add DL; WX; WY 1; 0.63; 0.63
8 Comb7 Add DL; WX; WY 1; 0.63; -0.63
9 Comb8 Add DL; WX; WY 1; -0.63; 0.63
10 Comb9 Add DL; WX; WY 1; -0.63; -0.63
11 Comb10 Add DL; LL; WX 1; 0.9; 0.9
12 Comb11 Add DL; LL; WX 1; 0.9; -0.9
13 Comb12 Add DL; LL; WY 1; 0.9; 0.9
14 Comb13 Add DL; LL; WY 1; 0.9; -0.9
15 Comb14 Add DL; LL; WX;WY 1; 0.9; 0.63; 0.63
16 Comb15 Add DL; LL; WX;WY 1; 0.9; 0.63; -0.63
17 Comb16 Add DL; LL; WX;WY 1; 0.9; -0.63; 0.63
18 Comb17 Add DL; LL; WX;WY 1; 0.9; -0.63; -0.63
11 Enve Enve Comb1; comb2; 1;1; …;1
… comb17
f. Define MASS SOURCE
Menu Define > Mass source or click
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II. MODELING AND ANALYSIS
2.1. Modeling columns, beams, walls, slabs…
a. Draw walls:
- There are 2 ways to draw walls in a plan:
M1: Menu: Draw→ Draw Area Object →Create Walls in Region or at Click
(Plan) or click.
M2: Menu: Draw→ Draw Area Object →Create Walls (Plan) or click
- Need to draw points (at begins and ends of walls) (menu Draw → Draw Point Object
or click )
- Add grids at all new points:
Select all points.
Menu Edit → Edit Grid Data → Add Grid at Selected Point; choose Parallel to X.
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Similarly, select all points, Menu Edit → Edit Grid Data → Add Grid at Selected
Point; choose Parallel to Y.
- Draw wall in center:
Set plan view: Story 2
Draw walls: Menu Draw→Draw Area Object →Create Walls in Region or at
Click (Plan) or click to draw as follow:
- Draw spandrel:
Add Reference Plans at the height -0.8m; 2.2 m; and 6.2m. Menu: Edit→ Edit
reference Plans
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Set elevator view: elevation 3.
Divide walls at reference the plan. Select 3 walls as the picture. Menu: Edit
→Mesh areas
Draw spandrel in the elevation 3: Menu Draw→ Draw Area Object → Draw
rectangular Areas (Plan, Elev) or click.
Draw similarly for story 3,4.
Copy walls in story 4 to remain stories.
- Draw other walls:
Set plan view: Story 2
Choose All Story
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Menu: Draw→ Draw Area Object →Create Walls in Region or at Click (Plan)
or click
b. Asign pier label:
Choose one or many walls.
Menu: Assign → Shell/Area → Pier label
c. Draw main beams of model:
Set plan view > Story 1
Turn into mode: all Stories
Menu Draw > Draw Line Objects > Draw Lines in Region or at Clicks (Plan,
Elev, 3D) or click
Or Menu Draw > Draw Line Objects > Draw Lines (Plan, Elev, 3D) or click
d. Draw Columns of model:
Modify similar story in Edit story data: menu Edit→ Edit Story Data→ Edit
Story or right-click on screen and choose Edit Story Data.
Set plan view > Story 1
Turn into mode: Similar Stories
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Menu Draw → Draw Line Objects →Create Columns in Region or at Click
(Plan) or click
Turn into mode: One Story
- Set Building View Options:
Menu View →Set Building View Options hoặc Click
e. Draw slabs of model:
- Draw slabs:
Set plan view > Story 1
Turn into mode: all stories
Menu Draw → Draw Area Objects.
- When drawing slabs, remember to MESH SLABS
Select slabs (usually all slabs).
Menu Asign→Shell/ Areas/ Asign Object Auto Mesh Options
Checking Mesh slabs: View →Set Building View Options or Click
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Note: need to add more secondary grids to get the better result of meshing slabs.
Select the point that the gird will go through
Menu: Edit → Edit Gird Data→ Add Grid at Selected Points
Mesh slabs again.
Divide a slab into separate slabs
Select a slab needed to be divide (select a line if want to divide at this line)
Menu Edit →Mesh Areas
- Assign ridgid diaghram
Choose all slabs. Men Assign → Shell/Area →Ridgid Diaghram or click
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2.2. Assign Restrains (Supports)
Choose points that need restrains.
Menu Assign → Joint/Point→ Restrains (Supports) or click
Fully supported: All degrees of freedom are restrained
Pinned: All three translational degrees of freedom are restrained
Roller: Only the vertical (translation 3) degree of freedom is restrained.
Fully free: All degrees of freedom are unrestrained.
Note: if there is a wrong restrain, ......
Checking the model before assigning loads:
- Checking model: Checking numbers, sections, restrains…
2.3. Assigning loads
There are 3 ways of loads regarding objective that loads affect: Joint/Point loads;
Frame/Line Loads and Shell/Area Loads. And Frame/Line Load includes Points or
Distributed Loads.
DEAD LOAD includes self-weight; wall loads and super dead load.
- Super dead load:
Select slabs.
Menu Assign → Shell/Area Load→ Uniform
- Wall loads
Turn off slabs and columns. Select beams
Menu: Assign →Frame/Line Loads → Distributed or click
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LIVE LOAD
Select slabs.
Menu Assign → Shell/Area Load→ Uniform
2.4. Show/display Loads
Show point loads or distributed loads of Frame/line Loads: Menu Display > Show Loads >
Frame Lines> Show Frame/Line Loads
Show loads of Shell/Area Loads: Menu Display > Show Loads > Shell/Area Loads
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2.5. Set analysis Options and Run.
- Menu: Analyze→ Set analysis Options:
- Save and Run: Menu Analyze → Run Analysis or press F5
III. NATURAL FREQUENCY AND MODE SHARP
3.1. Natural frequency.
Menu: Display >Show table > Choose table for display and choose Modal
Information and Building Output
a. Modal Information Factors
Note: unit of periods is “s” (second)
b. Building Mode
Note: there is no unit of displacements.
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c. Center Mass Rigidity
Note: unit of Mass is kN_s2/m
3.2. Mode sharp.
Menu: Display > Show mode sharp
Mode 1 Mode 2
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Mode 3 Mode 4
Mode 5 Mode 6
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IV. WIND LOADS AND INTERNAL FORCE
4.1. Wind loads.
Unlock Model by clicking symbol
Wind load X: Menu Define > Static Load Cases and modify:
Wind load Y: Menu Define > Static Load Cases and modify:
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Note: X-Ord; Y-Ord coordinate of the wind force.
- Save and Run: Menu Analyze → Run Analysis or press F5
4.2. Internal force.
a. Show Deformed Shape
Menu Display→ Show Deformed Shape or click:
b. Show Member Forces/Stress Diagram.
Display objective that is wanted to display.
Menu Display > Show Member Forces/Stress Diagram >
Frame/Pier/Spandrel Forces or click and choose Frame/Pier/Spandrel
Forces
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c. Show Support/Spring Reactions
Menu Display > Show Member Forces/Stress Diagram > Support/Spring
Reactions or click-left and choose Support/Spring Reactions
d. Export to Execl.
Menu Display →Show tables
Choose Displacement or/and Reaction or/and Frame Output.
Choose Load Cases.
After click “Ok” There is a dialogue box
Note: Copy (Ctrl + C) to excel to handle.
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e. Export to File.txt.
Menu File → Print Tables → Analysis Output.
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