Structural Modelling using Etabs 2018

The architectural drawings for a G+7 residential building in zone 5 has been provided. The floor plan is the same for all 7 floor levels. Possible column positions have also been provided. Conceptualize a framing plan layout and then model the building in Etabs. The following architectural drawings have been provided:

• Typical floor plan – The location and thickness of the brick walls and the use of the
  space (for estimating live load) can be obtained from this plan
• A building section through the staircase and lift core is provided
• Parking layout in the ground floor – the column/shear wall arrangement must not
  obstruct entry/exit of vehicles.
  The following loadings are to be taken into account:
• Brickwall made of AAC blocks
• Finishes – floor tiles of 75 mm thickness
• Live loads as per IS 875 part 2
• Water tank of 20 KL above the staircase at Mumty level
• Lift Machine room at mumty level above lift core

The structural model must comply with provisions of IS 1893 and IS 13920.
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.

Please note that the column positions shown in the architectural typical floor plan are only to provide an initial starting point for modelling. Participants will have to change its size, introduce shear walls, and add new vertical elements after running the analysis. You will have to run the analysis multiple times until a structural model is obtained that meets structural code requirements without compromising architectural functions. Also, there is no one ‘correct’ structural system for this challenge. There can be multiple possible solutions for this problem.

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.

Step 1:

Open the ETABS Software.

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.

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.

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:

Goto 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,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.

Select Display and Click on show table

Unlock the model.By using the base reactions adjust the scale factor in response spectrum.

After that run the analysis and see the inter-story drifts.The Drifts should be with in 4%.

Base Shear is grater than 80%.

Therefore analysis has been done successfully.