Introduction to Etabs:
Etabs is a very useful software in the field of civil engineering. It is the most used software in structural engineering for the design of buildings, bridges and more complex analytical models. It features a powerful graphical user interface. It is used for linear, non-linear, static and dynamic analysis and design of the building systems. Etabs is best for designing of simple 2D frames as well as performing a dynamic analysis of complex high-rise structures and shear walled buildings.
Using etabs you can:
1. Create and modify a model
2. Exectue the analysis
3. Design a model as well as optimize the design
4. It displays results in graphical forms and also display real time-history displacements and generate reports.
How to Install etabs:
The installation procedure for Etabs is quite simple as compared to other structural engineering softwares, you don’t have to remember a number of steps to install and crack the software. Just follow these simple steps:
1. First of all double click the “setup.exe” file from the Etabs setup folder or CD.
2. When the installation is complete, run the “Etabspatch.exe” file.
3. Now double click the following icon on your desktop.
The program will work.
Here for sample I am using the version Etabsv9.7.1 (non-linear). All the tabs and windows shown in this tutorial are from this version.
When you open Etabs for the first time, it gives you “Tip of the Day”. Etabs gives you useful tips regarding the use of software.
You can uncheck the box at the bottom if you do not wish to receive these tips. However I recommend you to check the box.
Different Features of etabs:
1. Windows Drop Down Menu
2. Windows Tool Bar
3. Complete black screen of Graphical User Interface.
4. Command Tool Bar
5. Etabs gives you three views of your model (Plan, Elevation or 3D) and also the extruded view (click and check the box “extrusion” and “object fill” and then click apply to all windows)
6. Model can be rotated in 3D using this tab .
7. By clicking this tab repeatedly, you will be shown different sides of the 3D model or the plan one by one .
8. There are the too many zooming options. First one is for Rubber band zoom,second to Restore full view, third to Restore Previous zoom, fourth to zoom in one step and last is to zoom out one step.
9. Whichever section you want to select for a particular task e.g Replication, just go to Select→frame section or wall/slab/deck section or any one of your choice, only those section will be selected in your whole model.
Here I am going to teach you the steps for making any model in etabs. At the end you will realize how easy it was.
First step is to click on File→New Model
A dialog box will appear.
Click on Default.edb. Now another box appears.
Click on Custom Grid and then on Edit Grid. A new box appears.
Here enter all the X and Y Co-ordinates i.e the co-ordinates of plan according to the autocad drawing of the structure and click Ok. Now click on Custom Storey Data to enter the co-ordinates of Z-axis i.e elevation in the same way and click Ok. Then select your units. I have hosen Kip-ft. In the Add Structural Object tab, choose Grid Only. Click Ok. Now your grid will be displayed on screen.
Second Step is to Define the Material Properties i.e define the materials used/planned to be used in your structure. Click Define→Material Properties.
The following dialog box will appear.
Click on Add new Material. However Concrete and Steel are already defined by default. For them you can click on Modify/Show Material and set your desired properties e.g color, poisson’s ratio, coefficient of thermal expansion, shear modulus etc.
Third Step is to define the Frame Sections. Here you will define the beams and columns you have used or proposed for the building. Click on Define→Frame Sections
Now click on Add Rectangular.
Another dialog box will appear.
Type the name of the frame section e.g Beam, Column. and write down the dimensions of the beam or column.
Now click on Concrete Reinforcement and in the following dialog box select Beam for beams otherwise Column is already selected by default.
Then click “Ok” and close the dialog boxes.
Fourth step is to define the Area or Shear Wall sections. Go to Define→Wall/Slab/Deck sections.
This window appears.
Click on modify if your desired area section has been already defined or click add new slab or wall or deck.
Type the section name, material, thickness (membrane and bending) and Type. Then click Ok. Note that you will write the value of bending which is membrane thickness minus one inch.
Fifth Step is to define the loads. Go to Define→Static Load cases.
Dead and Live loads are already defined. Add other loads by writing their names one by one in Load and choose their type. For Example I have written SDEAD for Super Imposed Dead Load, and chosen the type Super Dead. Also define Earthquake Loads in X and Y directions. For them select auto lateral load according to the code you are following. I have chosen UBC 97. Now highlight the quake loads one by one and click on Modify Lateral Load. The following box will appear.
Here you can provide info about direction of earthquake, soil type, earthquake zone, time period, importance factor and overstrength factor. Set the parameters according to your structure. Click Ok to close the dialog boxes.
Sixth Step is to define Load Combinations. Go to Define→Load Combinations.
This window appears.
Click on Add New Combination.
Choose the load combination type. For ACI combinations you will choose Add.
You can also choose the default combinations already defined in the software. Go to Define→Add Default Design Combos and select according to your structure.
Seventh step is to defne Mass Source. Go to Define→Mass Source.
Choose From Loads and enter all the dead loads you have defined in the static load cases. Click Ok.
Now all the data have been added and now you have to place Beams, Columns and Slab (and shear wall). you can move up and down in each story of the building with the help of these tabs .
For a symmetric building, i.e if beams, columns, slabs etc are placed at same locations in each story then you do not have to place beams, columns, slabs etc manually one by one in each story. You can “Replicate” by making window (in window the beams should b selected) and click on Edit→Replicate. The following window appear.
You can enter the required amount of replication.
Eighth Step is to draw the line elements i.e beams.
Click on the command tool bar and the following box appears.
Now place the beams in the plan with the help of pointer according to the autocad drawing you are following.
Next draw the Columns.
Click on on the command tool bar and place columns either in plan or in elevation.
Now place the slabs in the plan. Click on on the command tool bar.
The following window appears.
The slab should be drawn by clicking once in the slab regions or also by selecting Draw Areas option from command tool bar, click one by one on the corner points in an anti-clockwise pattern and then press enter. Slab will be shown in gray color (if you have chosen ‘objects fill” discussed in the start).
Now your model is almost complete.
Nineth step is to provide joint restraints. Select the column foundations (in the Basement) by making window and go to Assign→Joint/Point→Restraints/Supports.
The following window appears.
Choose Fixed in Fast restraints and click Ok.
Tenth step is to mesh the areas. Go to Select and click on Wall/Slab/Deck areas and then choose slab. Slabs of whole model will be selected. Now go to Edit→Mesh Areas
This window appears. Division of areas into 2×2 is reasonable. Click Ok.
Then provide End Length Offsets to all the beams and columns. For this go to Select→By Frame Sections and select the beams and columns you have used in your model by holding “Ctrl” button on the keyboard.
Then go to Assign→Frame/Line→End(Length)Offsets.
This window appears. Click on Automatic from Connectivity and click Ok.
Now assign the loads one by one to the areas. Make selection of slabs of the whole model in the same way as described earlier and then go to Assign→Area/Slab Loads
This window appears. Enter the loads magnitudes.
In the same way assign all the loads one by one.
Here comes the last step, Run the Analysis.
A report will be generated. Play the animation to see the vibrations of your model under the action of different loads one by one. Find out the faults in your model. using this tab, click Start Design Check of Structure. Check from the analysis results which of the elements in your model tend to fail. To fix them, unlock your model and again go to Define Frame Sections and modify them i.e increase their sizes. Then run the analysis again. Your model should be having optimize sections.
These tabs will show you the undeformed, deformed shapes, Mode shape and member/forces stress diagram.
You can see the rendered view by clicking on View→Create OpenGL View
That was all about etabs. If you further need any guidance or have queries, do tell me, I will help you. Keep on practicing and you will explore more and more in this software. Good Luck!!