Structural Modelling using Etabs 2018

Structural Modelling using Etabs 2018

AIM:-

1. Conceptualize a framing plan layout and then model a G+7 residential building in zone 5 using Etabs software.
2. The structural model must comply with provisions of IS 1893 and IS 13920
3. Finally Run a modal response spectrum analysis and check 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.

PROCEDURE:-

STEP 1.

• Carefully analyse the floor plan and section of given residential model.
• Open Etabs software and open new file.
• Make the settings as below.

• Now enter all the sufficient grid and storey details in the following window.

• Then grid appears as follows in the screen.

Step 2:-

• Now go to define tab.
• define materail properties as follows.

Step 3:-

• Now again go to define tab.
• Then define all section properties such as Beams(B300x400),column(400x600) , (slab 115 and str 200) and shear walls.

1.Beams(B300x400)

2.Column(400x600) and (400x400)

3.(slab 125 and str 200)

4.Shear walls.

STEP 4:-

• Placing appropriate elements on the grids.

1. Placing Column(400x600)

2. Placing Beams(300x450)

3. Placing Shear walls(300)

3. Placing slab membranes.4

Step 5:-

• Now go to base floor and select all joints.
• Then go to Assign>joints>restraints>fixed.

Step 6:-

• Go to define>load patterns.
• Load patterns- dead,live,wall,floor finishes and seismic loads.

1. Brick wall - 3.5 KN/m^2
2. floor finishes - 1.5 KN/m^2
3. Live load - 2 KN/m^2 and 3 KN/m^2.

1. Brick wall - 3.5 KN/m^2

2. Live load - 2 KN/m^2 and 3 KN/m^2.

3. Floor finishes.

Step 7:-

• Select live reduction factor for each storeys as per IS code specification.

Step 8:-

• Define mass source as follows.
• 
• 

Step 9:-

• Define responce spectrum function.
• Go to deine>Responce spectrum>Func name_RS>OK.
• Then go to load case>add new case>Rsx(U1)>load case type>Response spectrum>Then fill load applied details.
• Similarly add another load case Rsy(U2).

Step 10:-

• shear walls are marked with appropriate names as follows.

Step 11:-

• Analyse>Check model.

• Run analysis

Step 11:-

• Go to Display>structure output>Base reactions.

From the table;

Eqx = 3766.2361 KN

Rsx = 1134.7834 KN

Hence scale factor = Eqx / Rsx = (3766.2361/1134.7834 )= 3.31.

similarly

Eqy = 3766.2361 KN

Rsy = 907.6078 KN

Hence scale factor = Eqy / Rsy = (3766.2361/907.6078 )= 4.14.

Now change the scale factor in the load case by mulitiplying the values obtained above.

Here we can see that the Eqx and RSx values are almost equal.

STEP 12

• Again Go to Display>structure output>Modal information>Modal participationg mass ratios.

Mode 1:- 29.31 %

Mode 2 :- 69.42 %

Mode 3 :- 28.32 %

First 2 fundamental modes are greater than the third mode.

Step 12:-

• Go to display>story response plot > Maximum story drift.
• Masimum story drift for Rsx and Rsy are as follows.

• Drift values are slghtly greater than 4%.

Step 12:-

• Go to base floor>Click on reaction tab>select load case and tick on display results for these componeents.

Eqx

Eqy

• Base shear taken up by the shear wall divided by total base shear of buliding will get the % of the shear forces taken up by the shear wall.
• And if it is less than 80% more shear walls have to be added.

Axial force diagram

• Display>Force stres diagram >Frame/pier/sprandel/link.

Result:-

• Hence G+7 Building has designed as per IS 1893 and IS 13920
• After framing the layout,analysis has been carried out.
• All the checks as per IS code has carried out.