Challenge

Structural Modelling using Etabs 2018

SSornala Munesh28 Nov 2022

The architectural drawings for a G+7 residential building in zone 5 have 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 typical architectural 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 G+7 residential plan from given architectural drawings using Etabs 2018.
To Run a modal response spectrum analysis and check analysis results of the etabs model.

INTRODUCTION:

ETABS is an engineering software product that caters to multi-story 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.
Basic or advanced systems under static or dynamic conditions may be evaluated using ETABS.
Interoperability with a series of design and documentation platforms makes ETABS a coordinated and productive tool for designs which range from simple 2D frames to elaborate modern high-rises.
Once modelling is complete, ETABS automatically generates and assigns code-based loading conditions for gravity, seismic, wind, and thermal forces.
Users may specify an unlimited number of load-cases and combinations.
Analysis capabilities then offer advanced nonlinear methods for characterization of static-pushover and dynamic response.
Dynamic considerations may include modal, response-spectrum, or time- history analysis.

PROCEDURE:

STEP: 1

First open the etabs software.
Next click on the file option at the left side top corner and select the new model, as shown below.

After selecting the new model, the new tab opens, in that tab we have to select 'Use Built-in Settings with option, as shown below.

After setting the model Initialization the templates tab will open and, select the Grid only and press ok.

Next, we need to do the settings in Grid system data, as shown below.

Next, we need to add the stories up to 7 story in the Story Data, as shown below
The 7 stories are added in the Story Data, as shown below.

Step: 2

Next the plan views are visible in the etabs screen, as shown below.
also open the 3D view

Step 3

Now go to file option and save the project as shown below.

STEP: 4

Next, we need to define option and select material properties, as shown below
After selecting the material properties, the new tab appears, then we add new materials by selecting the Add new material option, as shown below.

STEP: 5

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

so, go to define< material properties < add new material < India< concrete < Indian < M25

Next, we need to check the material property data, as shown below.

STEP: 6

Now we need to add new material types such as rebar and grade HYSD Grade 415.
Next, we need to check the material property data, as shown below.

Now we need to add new material type as rebar and grade as HYSD Grade 500
Next, we need to check the material property data, as shown below.

STEP: 7

• Now, go to define < section properties < frame section < add new ... as shown below.

After selecting the Add New Property, the new tab appears.
In that new tab we select the rectangular shape type in concrete.

Next the frame section property data will be visible.

In that we add beam size as BEAM250x450, change the material
Next, we need to select the Modify/Show Rebar option as shown below.
After selecting the Modify/Show Rebar option the new tab appears, in that we select the design type as M3 Design only (Bearn)
Next, we select longitudinal bars with the grade of HYSD500
Next, we select Confinement bars with the grade of HYSD415

Similarly, add new material < select rectangular shape type in concrete, as shown below
Next the frame section property data will be visible, in that we add column size as BEAM300x500, as shown below.
Next, we need to select the Modify/Show Rebar option as shown below.
After selecting the Modify/Show Rebar option the new tab appears.
In that we select the design type as M3 Design only (Beam).
Next, we select longitudinal bars with the grade of HYSD500
Next, we select Confinement bars with the grade of HYSD415

STEP: 8

REPEAT SAME STEPS AS USED IN CASE OF BEAM
we have to add the column size as 400x600 in the frame section property data, as shown below.

STEP: 9

Next FOR slab section from section properties
go to define < section properties < SLAB section < add new ... as shown below.

Next the slab properties tab will be visible.
In that we select the Modify/Show Property option, as shown below
After selecting the Modify/Show Property option, the new tab appears.
In that we need to put the slab name as Slab 125, it means slab with the thickness of 125mm.

And we take the concrete grade as M25, as shown below.
Next, we have to click the ok option.
Similarly, we take the slab thickness separately for staircase with the thickness of 200 mm

STEP: 10

go to define < section properties < wall section < add new ... as shown below.
Next, we have added the wall properties in the wall property data

STEP: 11

Next, we need to add the columns using the quick draw column option as shown below.

Next, we need to add the beams using quick draw tool

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

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

STEP: 11

Now we go to the base plan and select all base joints.
Next, we select the Restraints from joint option, as shown below.

Now we need to select the fixed joint and click on apply and then click on close button, as shown below.

STEP: 12

Next, we need to select the load patterns from the define option, as shown below.

Now we should add Dead load, live load, Brick wall load, and earthquake load, as shown below.

STEP: 13

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

Then after the new tab will appear, in that we select load pattern as Brick wall, and we take uniform load as 3 kN/m and then click on the apply button and close.

STEP: 14

Next, we have to click on the assign option and then select shell loads, from the shell loads we select the Uniform option, as shown below.

Here we apply the live load for the staircase portion, Varanda, and lift core area.

Next, we apply the live load for the remaining portions in the residential building, as shown below.

STEP: 15

• 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

STEP: 16

• 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.

STEP: 17

• 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

STEP: 18

• 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.

STEP: 19

Next, from the define option we select the load combinations, as shown below.

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, as shown below.

STEP: 20

Next, we select the Modal cases from the Define option, as shown below
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.

STEP: 21

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

After the model is checked, then the warning tab will be visible and it tells that there are no warning messages, as shown below

STEP: 22

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

After selecting the Response 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 modify show 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.

STEP: 23

• Next, we have to select the Load cases from the Define option, as shown below.

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 have to do the run analysis

STEP: 24

Next, from the display option we select the show tables option, as shown below.

After selecting the show tables option the new tab will be visible.
Now we select the Base Reactions and click on the ok button, as shown below.

The Base Reactions table will be visible, as shown.

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.]
After we enter these values for response spectrum as scale factors at X and Y directions in load case data, then the EQ is closer to the RS from the base reaction table, as shown below

STEP: 25

Next, from the display option we select the show tables option, as shown below.

After selecting the show tables option the new tab will be visible. Now we select the Modal Participating Mass Ratios and click on the ok button, as shown below.

Now the Modal Participating Mass Ratos table will be visible, as shown below

STEP: 26

Next, we select the Story response plots from the Display option, as shown below.

The story response for max story drift at X and Y direction, should not be more than 4%

STEP: 27

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 earthquake load towards X-direction (EQX) in the load case, then click on the ok button 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:

The structural model of the G+7 model is designed for given architectural planning using Etabs.

A frame model which satisfies both code provisions is analyzed

Columns, shear walls, and beams are provided in a possible symmetrical way without many offsets.

Analyses are done for modal number, base shear story drift aspect ratio, irregularity, etc.,

As per the analysis result, the building is a bit flexible on the y-axis, as Shear walls are sufficient to add additional columns as provided in the y-direction to meet the maximum story drift limit.

Structural Modelling using Etabs 2018

Ship work like this
in your own course.

Talk to a career counsellor

Ship work like thisin your own course.

Talk to a career counsellor

Ship work like this
in your own course.