Project 1_Comparative study of different storey buildings for Seismic forces
1.
Aim
To design a different storey of building with different column sizes as shown
And to get the results for
Procedure
- Open Etabs software.
- Then give the Indian settings and Code books.
- Then give grids and storey heights as required.
- Create material properties for concrete and steel.
- Then create section properties for beam and column section.
- Then create slab properties.
- Then provide load pattern as dead load, live load, wall load, earthquake load etc.
- Give mass source and dead load as 100%, Wall load as 100% and Live load as 25%.
- Then create load combinations.
- Use quick columns commends and select the column size and place it on the grids. Check all storey is selected.
- Then use quick beam commend and select the beam section and click on each grid the beams will be created. Check all storey are selected.
- Then give slab properties for similar selection.
- Then select beams and assign uniform wall load of 10kN.
- Then select slab and assign uniform live load as 3kN
- Then assign diaphragm for the structure.
- Once everything is assigned, then save and run analysis.
- Then go to file and save as the project and change the column size and assign the columns. Then run analysis.
- Then repeat the same procedure and modify the necessary changes given in the question.
- Do the same procedure for 10 given buildings with different parameters.
Output
Building A Column 400x400 Storey 2
Model B 5 Storey Building
Model C Storey Building with Column 550 x 300
Model D Column size 300 x 550
Model E 10 Storey with Column size 600x600 and 400x400
Model F Column 600x600
Model G 25 Storey with Column C400x400 C600x600 C800x800
Model H 25 Storey C800x800
Model I 25 storey with increase in the imposed load to 10%
Model J Increase in Imposed load to 20%
Thus, all the 10 models have been analyzed.
Result
|
Criteria |
Model |
Analysis Result Mode 1 Sec |
Conclusion |
|
Effect of stiffness on time period |
Building E (10 storey with varying column size) |
1.731 |
In Building E and F there is a marginal difference in Time period since the storey are less |
|
Building F (10 Storey with uniform column size) |
1.735 |
||
|
Effect of stiffness on time period |
Building G (25 storey with varying column size) |
4.17 |
Height of building is more the varying column size building is more stable than the uniform |
|
Building H (25 Storey with uniform column size) |
4.416 |
||
|
Effect of mass on time period |
Building H (25 Storey with 3kN/m imposed load) |
4.416 |
While changing the imposed mass for overall building there is marginal change in the time period. There is no significant difference in the time period. |
|
Building I (25 Storey with 3.3kN/m imposed load) |
4.425 |
||
|
Building J (25 Storey with 3.6kN/m imposed load) |
4.435 |
||
|
Effect of Building Height on Time period |
Building A (2 Storey) |
0.5 |
With increase in the height of building the Natural Time period also gets increases. When compared with 5 storey the natural time period will increase by 75% similarly there is a increase in time period of 60% when compared with 10 Storey |
|
Building B (5 Storey) |
1.036 |
||
|
Building F (10 Storey) |
1.735 |
||
|
Building H (25 Storey) |
4.416 |
||
|
Effect of Column orientation on time period |
Building B (All floor columns are 400 x400) |
1.036 |
In Building B the deflection is similar in both direction since the size of column is same. But in Building D the deflection is higher when compared to b, since the size of column in X direction is smaller in Building D |
|
Building C (All floor columns are 550 x300) oriented in X direction |
1.145 |
||
|
Building D (All floor columns are 300 x550) oriented in Y direction |
1.12 |
||
|
Effect of Flexural stiffness of structural element |
Building B Flexural stiffness of beams close to nil |
2.627 |
When we reduce the stiffness of beams then it will lead to lateral failure of building |
|
Full flexural stiffness of beams |
1.036 |
||
|
Effect of Axial stiffness of vertical member |
Building H Axial cross section for columns is close to nil |
5.991 |
Column is very important structure for taking the gravity load. If the cross section is close to zero then the structure will undergo complete collapse |
|
Full axial cross section for columns |
4.416 |
||
|
Effect of Degree of fixity of column bas on mode shape |
Building B Column Support Pinned |
1.03 |
The more the fixity of column the time period will get reduced. |
|
Column Support Fixed |
0.941 |