Structural Modelling using Etabs 2018

Question -

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.

Answer -

Aim -

To model and analyze the G+7 Residential building from the given architectural drawings.

Introduction -

Etabs is na engineering software product that caters to multy storey building analysis and design.

Modelling tools and templates, code-based load prescriptions, analysis methods and solution techniques, all coordinate with the grid like

geometry unique to this class of structure.

Modelling features that sreamline analytical model generation and simulate advanced seismic systems.

Once modelling is completed, Etans automatically generates and assigns code based loading conditions for gravity,seismic,wind and thermal

forces.

Procedure -

Step 1.

First we have to open the ETABS software.

Next click on the file option at the left side top corner and selelct the new model.

After selecting the new model new tab opens, in that tab we select Use built with setting with option.

After selecting the model initialization the tempates tab will opens and select the grid only and press ok.

Next we need to do the setting in grid system data.

Next we need to add the storeys upto 7 Storey in storey data.

Step 2.

Next the plan view are visible in the etabs screen.

Next we need to open the D view.

Step 3.

Next we need to define option and select the material properties.

After selecting the material properties the new tab appears, then we add new materials by selecting the add new material option.

Step 4.

Now we need to add material type as concrete and grade as M25.

Next we need to check the material property data.

Step 5.

Now we need to add material type as rebar and grade as HYSD 415.

Next we need to check the material property data.

Step 6.

Now we need to add material type as rebar and grade as HYSD 500.

Next we need to check the material property data.

Step 7.

Now we need to slelect the section properties and click on the frame sections.

Step 8.

After selecting the frame section new tab will be visible, in that we selelct the add new property.

After selecting the add new property new tab appears.

In that new tab we select the rectangular shape in concrete.

Next the frame section property data will be visible, in that we add the beam size as 250 x 400.

Next we need to select the Modify/show rebar option.

After selecting the Modify/show rebar option, new tab appears, in that we select the design type as M3 design only.

Next we select the longitudinal bars with grade of HYSD500.

Next we select the Confinement bars with grade of HYSD415.

Again we select Rectangular shape type in concrete.

Next the frame section property data will be visible, in that we add the column size as 300 x 500.

Next we need to select the Modify/show rebar option.

After selecting the Modify/show rebar option, new tab appears, in that we select the design type as M3 design only.

Next we select the longitudinal bars with grade of HYSD500.

Next we select the Confinement bars with grade of HYSD415.

Step 9.

Next we add column size as 400 x 400 in the frame section property data.

Again we have add the column size as 400 x 600 in the frame section property data.

Step 10.

Next we add the slab section option from the section properties.

Next the slab property tab will be visible, in that we select the Modify/Show property option.

After selecting the Modify/Show property option, the new tab appears.

In that we need to put the slab name as Slab 1, it means slab with thickness of 125mm.

And we take the concrete grade as M25.

Next we click on the ok option.

Now we take the slab thickness seperately for staircase with the thickness of 200mm.

Step 11.

Next we have the add wall properties in the wall property data.

Step 12.

Next we need to add the Column using the Quick draw column option.

Step 13.

Next we need to add the Beam using the Quick draw column option.

Step 14.

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

Step 15.

Next we need to add the shear walls in required locations in the residential buildings.

Step 16.

Next we need to add the Slabs using the Quick draw column option.

Step 17.

Now we go to the base plan and select all the base points.

Next we select the restraints from the joint option.

Next we need to select the fixed joint and click on apply and then click on close button.

Step 18.

Next we need to select load patterns from define option.

Now we should add the dead load, Live Load, Brickwall Load and Earthquake Load.

Step 19.

Next we need to select the distrubuted load from the frame loads.

Then after the new tab will appear, In that we select load patterns as Brickwall and we take uniform load as 3.5 kn/m and then click on the

apply button and close.

Step 20.

Next we have to click on assign option and then select shell loads, from the shell loads we select the uniform option.

Here we apply the 3kn/m^2 live load for the staircase portion, varandha and lift core area.

Here we apply the 2kn/m^2 live load for the remaining portion of the residential building.

Step 21.

Next we have to select live load reduction factors from the design option.

Now we add the reduction factor by decreasing 10% from the 1st Floor to 7 Floor.

Step 22.

Next, from the define option we select the mass source.

Next we add the load patterns in the mass source data.

Step 23.

In the select option we select object type option.

After selecting the object type option, new tab will be visible, in that select the floors and click on the select button and close.

Next we have to select the Diaphagrams from the shell option.

After selecting the diaphagrams the new tab will be visible, in that select D1 and click on the apply buttton and close.

Step 24.

Next we have to select the pier label from the shell option.

Before going to the shear wall design we have to assign the names for the shear walls.

Step 25.

Next, from the define option we select the load combinations.

After selecting the load combinations the new tab is visible, in that we select Add default design combos option.

Next we select concrete frame design and concrete shear wall design in the add default design combinations.

Next we can see here that the load combinations are visible.

Step 26.

Next we have to check the model by clicking the check model option.

After the model is checked, then the warninng tab will be visible and it tells that there is no warning messages.

Step 27.

Now we select the response spectrum from the functions from the define option.

After selecting the Response spectrum the new tab is visble, in that we choose IS 1893- 2016 from the Choose function type and click on the

Modify/Show spectru option.

After selecting Modify/Show spectru option the new tab is open, in that we give the Function name as IS FUNCTION and remaining details

will be set by the software itself, we dont need to change any of the details in that response spectrum function tab.

Step 28.

Next we select the load cases from the define option.

Next the load cases tab will be visible, in that we select the Add new case.

Now we have to enter the details of the load case in the load case data.

Now we have to run the analysis.

Step 29.

Next from the display option we select the show table option.

After selecting the show table option the new tab will be visible.

Now we select the Base reactions and click on the ok button.

Next the base reaction table will be visible.

Here we have to check that EQ should be closer to the RS, to get the closer to each other we should calculate that (EQ/RS) x Scale factor of

Response Spectrum.

Now putting the values from table X directions and Y direction.

At X direction we get 30969.6

At Y direction we get 27835.5

We put the above values as scale factor for response spectrum at X and Y direction in the load case data.

After we eneter the values for response spectrum as scale factor at X and Y directions in the load case data, then the EQ is closer to the RS

from the base recation table.

Step 30.

Next, from the display option we select the show table option.

After selecting the show table option the new tab is open.

Now we select the modal participating mass ratio and click on the ok button.

Now thw modal participating mass ratio will be visible.

Step 31.

Next we select the storey response plots from the display option.

The storey response for maximum strey drifts at X and Y directions should not be more than 4%.

Step 32.

Next we open the plan view tab and select the base floor.

Next we have to open the reactions tab, then we select the earthquake loads towards X directions in the load case and click on the Ok

button

Now the base shear reaction will be appear.

When we divide the base shear taken up by the shear wall divided by the total base shear of building will get the % of the shear forces taken

up by the shear wall.

And if that is less than 80% then the more shear walls we need to add the structure.

Result -

The G+7 building has been modelled and analyzed successfully.