Modelling of 25 storey building with the specified properties using ETABS

AIM: ETABS modelling of a 25 storey building

Model a 25 storey building on ETABS with structural properties as specified below. Ground floor or plinth floor level can be taken at a height of 1.5 metres from the base. Each of the successive 25 storeys has a storey height of 3 metres.

PROCEDURE: 

STEP1

• Open E-Tabs ->new file
• A new tab will open
•  
• Use built in settings ->change the units and codes as per indian standard->Click Ok
• A new tab will open

STEP2

• Click on custom grid spacing->Edit grid data->A new tab will open

• Enter the grids ordinates in X direction And Y direction
• Click on Add to made more grids as pers requirement->Click on Ok
• You will be brought back to the previous page(Quick templates page)

• Click on custom storey data->A new tab will open

• Right click on and select "add new story"->Enter number of story you want->enter distance between them
• Select story 1 as the  master story and all athers as No(as shown in the above pic)
• Select siimilar to "Story 1"->SO that all other story will be similar to story 1
• Click Ok

 STEP3

• Will be taken to template page->click Ok
• The main page will open showing the building structure you designed(shown below)

STEP4 

• Click on Define bar->material properties->a new tab opens

• after selecting material properties->new tab will open

STEP5

• Click on add new material->New tab opens-.selct as per the standard(concrete/rebar etc.)

• Next we need to check material property data

STEP6

• Next we need to add rebar as the materail

• we need to check material property data of the HYSD bar

     

• click on OK                         

STEP7

• Also do the same for 415 rebar similar ot the abive 500HYSD

STEP8

• After adding the material properties->we have to add the column and beams sections
• Go to define->section properties->frame sections

• a new tab will open->Click on Add new property

 STEP9

• After click add new property->A new tab open ->from here select the rectangular concrete and click ok
• To add new beam and column frames

• Next a frame section property data will open->you have to enter the data for the beam and columns
• Change the property name as pers given data B300x400->change material in to M30
• enter the depth and widht of the sections

• Click on Modify/show rebar->to enter the rebars types and numbers
• A new tab will open->click on M3 design only
• Change longitudnal bars and Ties bar types to the one you made before
• Enter the covers distance ->click on OK

 STEP10

• Again on frame sections->Add new property
• Select the rectangular concrete section->click on OK
• A new tab open->rename the property as C800x800
• Enter the width and depth of the column

• Click on modify/show rebar->To enter the bars type of clumns
• A new tab will open->click on P-M2-M3 design->Enter longitudnal and tie bars type
• reinforcement  to be designed->Enter the number of bars your want in 2&3 direction

 STEP11

• Next we select the slab section for the slab of 150mm
• Go to define->section properties->slab sections

• A slab properties tab will open->Click on slab1 ->modify/Show property
• Slab property data tab will open->rename the slab as Slab150
• select the slab material as M30->Modeling type as "membrane" 
• enter the thickness of the slab->click OK

 STEP12

• Now we will add columns to the structure.
• Go to bottom right corner and select ALL STORIES
• Click on "Quick draw columns" of left side toolbars->a new tab will open
• select the C800x800 from the property

• select all the columns ->all the columns will be applied to the grids

STEP13

• Now beam will be added->Select quick draw beams (keep the selection to ALL stories)
• a tab will open->select the property to B300x400
• select all the beams section->the beams will be applied

STEP14

• Now add slabs to the section-Select quick draw floors/Slabs
• a tab will open->change the property to slab 150
• Change the selection To similar stories
• select all the slabs of any one floor ->the floors will be applied

STEP15

• Now joints will be added to the base
• Goto Assign bar->Joints->Restraints

• A new Joint assignment tab will open->select the pin joint

• Now the pin joint is assigned to the base of the columns

STEP16

• Now we need to define load patterns->Go to Define Bar "Load patterns"
• Add dead load ,live load,brickwall load and earthquake load as shown below

• Now we have to modify the earthquake load as per the direction of applications
• To modify ,click on earthquake loads "EQx-"  ->CLick on Modify lateral load
• A new tab will open-> select only the Load direction you want(X dir-eccentricity in this case)
• Select Site III as suggested in the question & time period user defined 0.5 sec

//Do this for all the earthquake directions,just change the eccentricity and direction in the above

STEP17

•  Now we have to assign the live load to the slabs and brick wall loads
• Select all the slabs of any floor
• Go to Assign->Shell loads->Uniform

• A Shell load assignment will open->Input a live load of 3 KN/m^2 as per the question
• Make sure the similar stories are selected

• Now the live load is applied to all the floors

STEP18

• Now the live load will be applied on the roof
• Go to the roof plan->Change the selection into One story
• select all the slabs of the roof
• Go to assign->shell loads->Uniform
• Put live load of 1.5KN/m^2 (the roof has live load of 50% of the floor)

STEP19

• Now assigning the brickwall load to the beams                       //Make sure u change the selection to all stories
• GO to select menu->object types->select beams(all beams will be selected)

• Now go to Assign menu->Frame load->distributed

• load assessment tab will open->select the brickwall from the selection
• enter the value of 10KN/m

• brickwall is districbuted all over beams

STEP20

• Now we define mass source
• Go to Assign Menu->MAss source
• A new tab will open->Click on Modify/show mass source
• modify tab will open->select specified load patterns
• Input dead=1,brickwall-1,live=0.25

STEP21

• Now load combination will be defined
• From the define menu->go to load combination
• a new tab will open->click on Add default design combos
• Select concrete frame design 

• Click oK

STEP22

• MAking the diaphragm of the structure
• Go to select menu->object types->seelct the floors
• Assign->Shell->Diaphragm

• A new tab will open->in that select D1 and apply

STEP23

• Now we check the model for errors
• Go to analyze menu->check model
• A new tab opens->tick all the checks

• A no error mesage will be shown if there are no errors in the structure

STEP24

• Now Go to analyze menu->run analysis->analysis will take some minutes

• Go to "Show deformed shape or F6"->Tab will open and select any case(live/dead,earthquake) you want view the deformed shape

//Check on all other cases and see the deformed shapes

STEP25

• click on Display menu->Show tables->TAbles display will open
• select anaylysis results->structure output->modal information->Modal participation mass ratios

• A Modal participation mass ratios table will appear with all the mass ratios action on the builidng

• From table Natural time period of mode1 is noted and torsional DOF is noted
• Tx1=4.6sec,Ty1=4.394sec and Txy=3.436sec
• so it is clear from the table that the torsional time period is less than the two translational time period as required by IS 1893 provision table 5

CONCLUSION:The analysis is done and the result is within the range