Structural Modelling using Etabs 2018

CHALLENGE 09

Aim:

To model and analyze the G+7 storey building using ETABS with application of proper load cases and load combinations for the given typical floor plan drawing.

PROCEDURE:

• Initially open the given architectural plan in Auto cad and study the plan & locate the postions of beams, column and shear walls.
  
  
  
• After done the postioning then the strctural plan should implemented in the Etabs software.

Step 1:

Open the ETABS Software.

• so, now open the etabs software and click on the new model option.
  
• It will appears a model initialization window, then select the Use Built-in settings with option and fill the units and codes as per the detailes we used.
  
• Then again it will appear another window-New model quick template. By using this tempate select the grids and storeys and respectivelty it dimensions also.

Set the Grid and storey details using editing options.Provide 4 grids at x-Direction and 6 grid at y-Direction with the proper spacing.

Step 2:

Now define each story and story height.

Step 3:

Click Define tab and select the materials.Choose the material type such as concrete for M25.

Step 4:

Similarly for Rebar material, Click define select add new material option and choose the type as Rebar.

Select Grade as HYSD grade 500.

Step 5:

Click define tab.Select frame section property

Provide the beam dimensions as 350 x 550.Then modify the rebar details.

Step 6:

Click define tab.Select frame section property

Provide the Column dimensions as 400 X 600.Then modify the rebar details.

Step 7:

Click define.Select Section properties.Click on slab sections.

Provide the thickness of the frame as 150mm.

Step 8:

Click define.Select Section properties.Click on Wall sections.

Set the thickness of the wall as 250mm.

Step 9:

By using the Quick draw column/beam option place the columns in the floor plan at each grid intersection.

Select all storey option.

Step 10:

Similarly draw the beams as per the floor plan.

Draw the shear walls in required places.

Step 11:

Click on the plan and select base.Select one story.

Slect all the column base.

Click on assign .Select joint.Select the joints as fixed.

Step 12:

By using the Quick draw floor/draw rectangular floor plan option place the floors.

Select all storey option in bottom tool bar.

Step 13:

Click on the load patterns and define dead,brick wall and live load.

Step 14:

Apply the brick wall load in all the beam component.

Step 15:

Apply live load as per IS 875.

Live load = 2kn/sq.m ( As per table 1 from IS 875 Part 2)

Live load = 3kn/sq.m for balconies ,lift area and walk -way ( As per table 1 from IS 875 Part 2)

At the roof we take only 50% of live load.

Step 16:

Similarly the reduction factor has been taken from clause 3.2.1 in IS 875 part 2

Step 17:

Click on the load patterns and define the sesimic loads.

Calculate the time period T value from IS 13920 clause no 7.6.2

Step 17:

Define mass source.

Step 18:

Select on all story option.Goto select -Objective type-Floors.Select all the floors.

Goto assign ,click on shell ,click on diaphragms.Assign the dia-phragms to all the floors.

Step 19:

Go to Define .Click on the pier labels and the pier labels.

Select the shear walls one by one and assign the pier labels.

Step 20:

Click on the load cases and define the no.of modes.

Step 21:

Click on the analyze, then click on the load cases to run.Tick mark the calculate Diaphragms centres of Rigidity.

Step 22:

Click on define ,select function and select on Response spectrum.

Define the response spectrum in both X and Y direction.

Step 23:

Select load combinations ,click on the default design combinations.

Step 24:

Select analyze and Click on check the model.After the Model checking Click on the Run the analysis.

MODAL PARTICIPATION RATIO CHECK

• After the completion of analaysis.Then Go to the display-show tables- analysis results-strctural ouitput-modal information - modal mass participating ratio.
  
• hence stasisfied the modal participation of translational mode- first two fundamental modes should be greater than the transional mode(third one).
  
  • mode1-0.6914
  • mode2-0.6396
  • mode3-0.6303

BASE SHEAR CHECK AND SCALING.

• Now, go to the base reactions.Go to the display-show tables-analysis result-strcture output-base reactions.
  
• `EQ_x= 1159.66kn & RS_x=1163.24`hence the scale factor is`1159.66/1163.24=0.996`
• `EQ_y=1265.75kn & RS_y=1128.56kn`hence the scale factor is `1265.27/1128.56=1.12`
  

CHECK FOR INTER-STORY DRIFT

• IN x direction:
  
  As per the codal provision os IS 1893: 2016 it doesnot exceed the 0.004
  we obtained 0.0022. so henece safe.
• In y direction:
  
  as per the codal provision os IS 1893: 2016 it doesnot exceed the 0.004
  we obtained 0.0023. so henece safe.

RESULT:

The structural model must completed with provisions of IS 1893 and IS 13920.
Run a modal response spectrum analysis and checked the analysis results of the etabs model for

• inter-storey drift requirements
• vertical & planar irregularities
• minimum shear wall requirements
• maximum axial load ratio for column and shear walls
• effective moment of inertia for beams and columns etc.

REPORT:

CHECKS	DESCRIPTION	REQUIREMENT	PROVIDED
1.Modal mass participation ratio	First three modes dominates at least 65%	X-direction 0.6914+0.0017+0.0038 =0.76=76%	Achieved
		y-direction 0.6396+0.1189+0.0132 =0.77=77%	Achived
2.Modal mass participation ratio	Mode1 and mode 1 are differ by at least 10%	mode1-0.6914 mode2-0.6396	Achived
3.modal mass participation ratio	Principle modes are greater than the transilational mode	mode1-0.6914 mode2-0.6396 mode3-0.6303	Achived
4.Base shear check	for x-direction	`EQ_x= 1159.66kn & RS_x=1163.24` hence the scale factor is`1159.66/1163.24=0.996`	Hence OK
	for y-direction	`EQ_y=1265.75kn & RS_y=1128.56kn` hence the scale factor is `1265.27/1128.56=1.12`	Hence OK
5.Inter storey drift check	as per the codal provision os IS 1893: 2016 it doesnot exceed the 0.004	X-direction=0.0022	Achived
		y-direction=0.0023	Achived