Project 1_Comparative study of different storey buildings for Seismic forces

PROJECT 1- Comparative study of different storey buildings for Seismic forces

Procedure to make any Modal

1. Open E-Tabs and go to new file
2. A new tab will open
3. Choose the built-in settings option and select the display units and codes.
4. After model intialization select the grid and story inputs from the New model quick templates dialogue box.
5. In this dialogue choose custom grid spacing and custom story data which is used to provide the inputs specified above.
6. Enetr X grid data at a distance of as per drawing.
7. Now edit the stories by using the user defined storey input, Storey 1 has be labelled as master storey and all above levels are labelled similar to that.
8. Select material properties under the define tab.
9. Define the materials of concrete M30 grade and steel of transverse reinforcement as 415 grade and longitudnal reinforcement as 500 grade.
10. Select Section properties under the define tab.
11. Click on the frame section and create a new property as beam and input the values as 300X400mm.
12. After the define properties for the column as and slab thickness as per modals
13. Next we select the slab section for the slab of 150mm
14. Go to define, select section properties, then select slab sections
15. Using the membrane property,slab size 150mm has been addded tothe list.Mebrane property will help to consider only slab weights and floor weights in analysis of structure while no stiffness component of flange advantage are considered during calculation.
16. Now define the load patterns: click on the define ta and click on load patterns.
17. Define the loads like dead load,live load,brick load,earth quake load in x direction and positive x and negative x and same loads in the Y direction also.Mention IS codes of respective load
18. Now go to mass source from the define tab.
19. Modify the mass source and tick mark the required loads.
20. Add load patterns and assign to the model
21. Now load combination will be defined
22. From the define menu-go to load combination
23. A new tab will open-click on Add default design combos
24. Select concrete frame design
25. Now we will add columns to the structure.
26. Go to bottom right corner and select ALL STORIES
27. Click on "Quick draw columns" of left side toolbars->a new tab will open
28. select the column as per modal from the property
29. select all the columns -all the columns will be applied to the grids
30. Now beam will be added-Select quick draw beams (keep the selection to ALL stories)
31. A tab will open & select the property to B300x400
32. select all the beams section-the beams will be applied
33. Now add slabs to the section-Select quick draw floors/Slabs
34. A tab will open-change the property to slab 150
35. Change the selection To similar stories
36. select all the slabs of any one floor -the floors will be applied
37. Similarly add live load of 10Kn/m2 on all the beams.
38. For that select all the beams from select object type beams.
39. Goto the frame load and click on the distributed load and enter the value as 10 Kn/m2.
40. Do the same for all the earthquake loads.
41. Assign the loads and select similar stories.
42. Click on shell load under the assign tab.
43. Click on live load and give value as 3kn/m2.
44. Click on apply.
45. For the roof we will take only 50% of the live load.
46. Now create the diaphragm by going to the assign tab then shell and select diaphragms.
47. Click on ok.
    

Result-

• Using analyze>run analysis,the model is analysed and deflection patterns,BMD/SFD patterns are cross checked logically.It is understood that the worked model provides reliable results
• Display>show tables>analysis results>structure output>modal information>modal participation mass ratios.
• The Tabe will visible for time period data.

Models and Their Comparative Analysis data for study

• Modal A- 2 storey 400 x400

• Modal B- 5 storey 400 x400

• Modal C- 5 storey 550 x300

• Modal D- 5 storey 300 x 550

• Modal E- 10 storey - upper 5 storey 400 x 400 & lower 5 storey 600 x 600

• Modal F- 10 storey - 600 x 600

• Modal G- 25 storey - upper 5 storey 400 x 400, middle 10 storey 600 x 600, lower 10 storey 800 x 800

• Modal H- 25 storey - 800 x 800

• Modal J- 25 storey - 800 x 800 imposed mass 10% larger then Modal H

• Modal K- 25 storey - 800 x 800 imposed mass 20% larger then Modal H

Effect onTime Period for all Modals

Modal A

Modal B

Modal C

Modal D

Modal E

Modal F

Modal G

Modal H

Modal J

Modal K

Effect of stiffness on T: Compare fundamental natural periods of buildings E & F as well as G & H. Why is there a marginal or significant difference in the fundamental natural periods.

Crietria	Model	Analysis Result	Conclusion
Effect of stiffness on Time Period	Building E- 10 storey with varying size of column	1.232 s
	Building F- 10 storey with uniform size of column	1.28 s
Effect of stiffness on Time period	Building G- 25 storey with varying size of column	3.36 S
	Building H- 25 storey with Uniform size of column	3.43 S

Effect of mass on T: Compare fundamental natural periods of buildings H, J and K. Have the buildings become more flexible or stiff due to change in mass

Criteria	Model	Analysis result	Conclusion
Effect of mass on Time period	Building H (25 storey with 3kn/m2 imposed load)	3.43 s
	Building J (25 storey with 3.3 kn/m2 imposed load)	3.437 s
	Building k (25 storey with 3.6 kn/m2 imposed load)	3.437 s

Effect of Building Height on T: How does the fundamental natural periods of Buildings A, B, F and H change with change in building height

Criteria	Model	Analysis Result	Conclusion
Effect of Building height on time period	Building-A (2 storey)	0.351s	Time period increases as Height of building increases. therefore Height of building is directly proportional to time.
	Building-B (5 storey)	0.729 s
	Building-F (10 storey)	1.28 s
	Building-H (25 storey)	3.43 s

Effect of Column Orientation on T: How does the fundamental natural periods of Buildings B, C and D change with change in column orientation

Criteria	Model	Analysis Result	Conclusion
Effect of Column Orientation on time period.	Building-B (All floor column sizes are 400 x 400)	0.729s	response of building in each direction is same.
	Building-C (All floor column sizes are 550 x 300 orientated in X direction)	0.806 s	response of building in x direction is more
	Building-D (All floor column sizes are 300 x 550 orientated in Y direction)	0.788 s

Effect of Flexural Stiffness of Structural Elements on mode shapes: Compare fundamental mode shape of Building B in two situations when flexural stiffness of beams relative to that of adjoining columns is very small versus when it is large.

Criteria	Model	case	Analysis Result	Conclusion
Effect of flexural strength of structural elements on mode shape	Building-B	Flexural stiffness of beam close to nil (zero interia)	1.846	If we don;t consider then the value get double
		Full Flexural stiffness of beam (Regular)	0.729s

fig: Flexural strength beam close to nil

Effect of Axial Stiffness of Vertical Members on mode shapes: Compare fundamental mode shape of Building H in two situations when axial cross-sectional area of columns is very small versus when it is large

Criteria	Model	case	Analysis Result	Conclusion
Effect of Axial Stiffness of Vertical Members on mode shapes	Building-H	Axial cross section for columns close to nil (zero axial area)	4.656
		full Axial cross section for columns (Regular)	3.43 s

fig: Effect of Axial Stiffness of vertical member

Effect of Degree of Fixity at column bases on mode shape: Compare fundamental mode shape of Building B in two situations when base of columns is pinned versus when it is fixed.

Criteria	Model	case	Analysis Result	Conclusion
Effect of Degree of Fixity at column bases on mode shape	Building-B	column support Pinned	0.729	more rigid support lesser the time period
		column support fixed	0.661

fig: Effect of degree of fixity