Structural Modelling using Etabs 2018

Structural Modelling using Etabs 2018Structural Modelling using Etabs 2018

Aim:

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

Procedure:

Step1: Creating a new file and saving it

• Open the etabs software
• Create a new model
• Now click cutom grid data and custom story data
• Enter the grid and storey data

• Now plan view is visible

• After that save the the model from the file tab
• Next we start the modelling

Step 2: Define the material Properties

• Now we define the material properties
• Goto define tab and select material properties
• Define concrete material M25, rebar material HYSD415 and rebar material HYSD500

Step 3: Define section Prperties

• Now we define section properties
• Goto define tab and the section properties
• select frame sections <rectangular section

• Select add new prperty
• Now add beam 250x450(B250x450), Beam 300x500(B300x500),Column 400x400(C400x400) and Column 400x600(C400x600)

• Now we add slab section
• Add slab of 125 mm thick as Slab125 and slab 200mm thick staircase slab as STR.slab which is a one-way slab

• Also define walls of thickness 250 and 300

Step 4: Apply the frames including the shear walls where required

• Now we add columns using quick draw column

• Next we need to add the beams using quick draw tool
• Also we use move and replicate commands to draw secondry beams as well

• Next we add the shear walls in required location in the residential building

• Next we need to add the slab using quick draw floor/wall option

• Goto the base view and select joints
• make the joints as a fixed joint

Step 5: Define and Assign Loads

• Now we define the load patterns

• Now we assign loads
• Next we need to select the distributed load from the frame loads, as shown below.

• Add 3.5 KN/m of Brickwall load

• Assign Live load of 3 KN on the slab

• Next we have to select live load reduction factors from the design option, as shown below.

• Now we add the reduction factor by decreasing 10% from 1st floor to 7th floor as shown below

• Next, from the define option we select the mass source, as shown below.

• Next we add the load patterns in the Mass Source Data, as shown below.

• In the select option we select object type option, as shown below.
• After selecting the object type option, the new tab will be visible. In that select the floors and click on the select button and close

• Next we have to select the Diaphragms from the shell option, as shown below

• After selecting the diaphragms the new tab will appear, in that select D1 and click on the apply button and close

• Next we have to select the Pier label from the shell option, as shown below

• Before going to the shear wall design we have to assign the names for the shear walls(P1 P2 P3 P4 P5 P6 P7 P8) as shown

• 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 & concrete shear wall design in the Add Default Design Combinations as shown below
• Now we can see here that the load combinations are visible

• Next we select the Modal cases from the Define option
• After selecting the Modal cases the new tab is visible. In that we give modal case name as Modal 1 & we give the maximum number of modes as 20, as shown below.

• Next we have to check the model by clicking the check model option as shown below

Step 6: Adding response spectrum, Run analysis and check the results

• Now we select the Response spectrum from the Functions from define option, as shown below

• After selecting the Respnse spectrum the new tab is visible, in that we choose IS 1893 2016 from the Choose function type and click on the Modify/Show spectrum option
• After selecting the modifyshow spectrum option the new tab will be visible. In that we give the Function name as IS FUNCTION and remaining details will be set by the software itself we don't need to change any of the details in that response spectrum function tab

• Next we have to select the Load cases from the Define option
• Next the Load cases tab will be visible, In that we select the Add new case as shown below

• Now we have to enter the details of load case in the load case data as shown below

• Now we run the Ananlysis

• Next, from the display option we select the show tables option

• After selecting the show tables option the new tab will be visible.
• Now we select the Base Reactions and click on the ok button.
• The Base Reactions 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) * Scale factor of Response spectrum.]

• Next we select the Story response plots from the Display option
• The story response for max story drift at X and Y direction, should not be more than 4%

• Next we open the select plan view tab and select the base floor, as shown below
• Next we have to open the reactions tab, then we select the eartquake load towards X-direction(EQX) in the load case, then click on the ok buttion as shown below

• Now the base shear reactions will appear, as shown below.
• 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 shea forces taken up by the shear wall
• And if that is less than 80%, then the more shear walls we need to add to the structure

Result

Hence, the G+7 building has been modeled with all the required conditions as per Residential building and has been analysied succesfully using ETABS.