Structural Modelling using Etabs 2018

AIM:

To model and analyze the G+7 residential building from the given architectural drawings using the ETabs software

INTRODUCTION:

ETABS is an engineering software product that caters to 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 unique to this class of structure. Basic or advanced systems under static or dynamic conditions may be evaluated using ETABS. For a sophisticated assessment of seismic performance, modal and direct-integration time-history analyses may couple with P-Delta and Large Displacement effects. Nonlinear links and concentrated PMM or fiber hinges may capture material nonlinearity under monotonic or hysteretic behavior. Intuitive and integrated features make applications of any complexity practical to implement. 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 modeling 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. P-delta effect account for geometric nonlinearity.

Given enveloping specification, design features will automatically size elements and systems, design reinforcing schemes, and otherwise optimize the structure according to desired performance measures.

STEP 1:

First we have to open etabs software and select new model in the file option at the left side top corner as shown below

Model intialization interface appears and select USE BUILD IN SETTINGS and make the below mentioned settings

An interface appears as shown in picture. Click the custom grid spacing and maintain the spacing as 4m in both x and y direction

In X direction draw 4 grids and in Y draw 6 grids as shown in the picture below

Click OK, a box appears

Now we need to add the stories upto 7 story in the story data. Enter the stories upto 7 maintaining height of 3m expect for base to plinth which is at 1.5m and 1st storey is entered as master story

STEP 2:

Next the plan views are visible in the etabs screen, as shown below

Next we need to open the 3d view as shown in the figure below

STEP 3:

Now go to define option in toolbar and select material properties as shown

After selecting the material properties the new tab appears and we add new materials by selecting the Add new materials option as shown below

STEP 4:

Go to add new material property option for M25 concrete

The properties of M25 as per IS code defined before gets displayed

STEP 5:

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

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

STEP 6:

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 selection properties and click on frame sections

STEP 8:

After selecting the frame sections the new tab will appear in that we need to select the add new property 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 as shown below

Next the frame section property data will be visible , in that we add a beam of size B250X450

Next we need to select the modify/show rebar option as shown

After selecting the option the new tab appears in which we select the design type as M3 desgn only (beam)

Next we select longitudanl bars with the garde of HYSD500

Next we select confinement bars with the grade of HYSD415

Again we have to select rectangular shape type in concrete as shown

Next the frame section property data will be visible , in that we add a beam of size B300x500

Next we need to select the modify/show rebar option as shown

After selecting the option the new tab appears in which we select the design type as M3 desgn only (beam)

Next we select longitudanl bars with the garde of HYSD500

Next we select confinement bars with the grade of HYSD415

STEP 9:

Now we have to add column size 400x600 in the frame section property data as shown

Now we have to add column size 400x400 in the frame section property data as shown

STEP 10:

Next we select the slab option

Go to Define > Section properties > slab section

Next the slab properties will be visible.In that we select the Modify/show property option as shown below

After selecting the option the new tab appears

In that we put the slab name as slab125 as the thickness of the slab is 125mm

We take the concrete grade as M25

Click OK

Now we take another thickness of the slab for the staircase as 200mm

STEP 11:

Next we have to add the wall properties in the wall property data, as shown below

STEP 12:

Next we need to add he columns using the uick draw columns option as shown below

STEP 13:

Next we need to add the beams using quick draw beams option as shown below

STEP 14:

Next we need to add the secondary beams by using quick draw secondary beams option as shown below

STEP 15:

Next we add the shear walls in required locations as shown below

STEP 16:

Next we need to add the slabs using quick draw slabs option as shown below

STEP 17:

Now we go to the base plan and select all base joints

Next we select the restraints from the joint option as shown below

Now we need to select the fixed joints and click aplly and close button as shown below

STEP 18:

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

Now we add dead load, live load, seismic loads, wall load as shown below

STEP 19:

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

Then after the new tab appears in that we select load pattern as brick wall and we take uniform load as 3.5KN/m and then click on apply 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 load option as shown below

Here we apply the 3KN/m2 live load for the stair case portion, veranda and lift core area

Next we apply 2KN/m2 live load on the remaining area of the residential building

STEP 21:

Next we have to select live load reduction factor 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 22:

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

Next we add the load pattern in the mass source data as shown

STEP 23:

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 disphgram from the shell option in the assign option in toolbar

After selecting the diaphgram the new tab will appear in that select D1 and click apply and close button

STEP 24:

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 as P1,P2......P7 as shown below

STEP 25:

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 assign "Add default design combos" option

Next we select "concrete frame design" and "concrete shear wall design " in the add default design combinations as shown below

Now we can see here the load combinations are visible as shown below

STEP 26:

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 and we give the maximum number of modes as 20 as shown below

STEP 27:

Next we have to check the modal by clicking the check modal as shown

After the modal is checked the the warning tab wll appear and it tells that no warning message is shown

STEP 28:

Now we select the resonse 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 option as shown below

After selecting the modify/show spectrum option the new tab will appear.In that tab give the function name as IS FUNCTION and remaining details will be set by the software itself we dont need to set hem up.

STEP29:

Next we have to select the load cases from the define option as shown below

Nex the load cases tab will appear 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 run anaysis as shown below

STEP 30:

Next from the display option we select the show tables option as shown

After selecting the shw tables option the new tab will appear

Now we select the base reactions and click on the ok button as shown below

Next the base reactions table will be visible as shown below.

Here we have to check the EQ showld be closer to RS to get closer to eah other we should calculate that (EQ/RS)XSCALE FACTOR OF RESPONSE SPECTRUM

Now substuting the values from the table at X direction (2844.6348/900.7656)x(9806.65)

At y direction (2844.6348/1002.1982)x(9806.65)

At x direction we get, 30969.6

At y direction we get 27825.15

We put the above values as scale factor for respnse spectrum at X and y directions in the load case data

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 RS from the base recation table

STEP 31:

Next from the display option we select the show tables options 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 ok

Now the modal participating mass ratios tables will be visisble as shown below

STEP 32:

Next we select the story response plots from the display option as shown below

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

STEP 33:

Next we open the select plan view tab and select the base floor as shown below

Now we have to open the reactions tab then we select the earthquake load towards X direction then click on ok button

Now the base shear reactions will appear as shown below

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

And if that is less than 80% then the more shear walls are needed to be added to the structure

RESULT:

The G+7 residential building has been modelled and analyzed sucessfully using Etabs software