Structural Modelling using Etabs 2018

Question:- STRUCTURAL MODELING USING ETABS

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 residential building in zone 5 from the given architectural drawings using the ETABS 2018.

INTRODUCTION :-

ETABS is an engineering software which is used to design multi-story building analysis and design. Modeling tools and templates, code-based load prescriptions, analysis methods and solution techniques, all coordinate with the grid-like geometry are all the features of this Etabs software.

PROCEDURE :-

1.Open Etabs software and go to File then New model then click on that.

After that Grid system data dailog box will open .Provide the grids as shown in attached picture.

Then click ok.

Enter the story details as per mentioned in the question.Make story 1 as master story and other stories similiar to story 1.

Then click ok to proceed.

Now you can see the model has been created as a grid system as per data entered.

Go to Define then Materials to create materials required for the model.

A dailog box will open ,click on the Add new material and enter the details of the required materials.

Then go to Define again then Section properties then Frame sections to add the frames for the model.

Create a new frame and name it as per data required. For beams select the M3 Design option and define the rebar material as Longi.bars as HYSD500 and Confinement bars as HYSD415.

then click ok.

Similarly do the same steps for columns also.

And then click on the Modify/Show modifiers.

For slab,

Go to define then section properties then slab sectiions

Then for wall sections

Go to Define then Section properties then wall sections.

Now to assign the columns

Click on the Quick draw column option and draw the columns as required

Select from the properties option and assign the columns

We need to add beam using the quick draw option.

Next we need to add secondary beams using the quick draw beams option.

Add the shear walls in required locations in the residential building.

Add the slab using the quick draw floor/wall option.

Then go to the base plan, Select all the base points. after that Go to assign, then joints, then click restraints. Then choose Fixed Joint and click apply, ok.

Now add dead load, live load, brick wall load, and earthquake load.

Select load pattern as Brickwall and take the uniform load as 3.5 kN/m. then apply ok.

Use the select option to choose all the floors. From the Shell option select the diaphragms

RESULT :-

Hence the model has been analysed and the following results are achieved for given conditions

1.Modal Mass Participation for first 3 modes must be 65%

Hence achieved.

2.Mode 1 and 2 differs by 10%

It is also achieved.

Principal modes must be greater than Torsional mode.

Achieved.

Inter storey drifts must be limited to 0.004

ACHIEVED

Now open the reactions tab, then select the eartquake load towards X-direction(EQX) in the load case, then click on ok .

The base shear reactions are now shown

When we divide the base shear which is taken by shear wall divided by the total base shear of building , it will get us the % of shear force taken up by the shear wall.

If it is less than 80%, then more shear walls are need to be added.

Here in our building it is sufficient.

Hence the modal has been created and analyzed successfully.