Project 1_Comparative study of different storey buildings for Seismic forces

Aim : To study and compare the results of

• Factors influencing the dynamic characteristics of different storey building for seismic force
• Factors influencing the Natural Period of different storey building for seismic force
• Factors influencing the Mode shape of oscillations of different storey building for seismic force.

 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. 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. 

Procedure:

Model A:

Step 1:

• In this , we are suggested to create 2 story buidling with said column and beam sizes.
• So to create the model.Open the new model and save the model as Model A.
• Now first of all we need to set the story and grid data to place the beams, column and slabs in the model.
• So go to edit setting in the tool bar and open edit story and grid settings.
• In that change the setting to customize grid and stroy data.First let us customize the grids which is going to be permanent grid setting throughout the model.
• As suggested we need 5 grids in the X direction adn 4 grids in the Y direction.
• The grid distance to be set in 4m between all grids.
• Thus created grid data is shown below

 

Step 2:

• After the creation of the grid data  we need to edit the story data.
• Now by choosing the edit story option.We need to creat 2 story excluding plinth and base.
• The story distance here we are setting as 3m between each story as standard story heights.
• To add story we need to right click on the arrow mark on the left side of the last story and edit the additional story settings.
• After adding the story to the existing story data.We need to make the story1 as master story not the plinth or base.
• As the remaining story to be marked as the similar story to story 1.

• Now we need to define the material properties of the components to be used in the model.
• To define the material prperties of the components we need to define the material to be used.
• So, go to the define option on teh tool bar and in the define option choose material properties.
• In material properties create a new material by clicking add new material.
• Now we need to create concrete material, in this whole project we are going to use M30 grade concrete as teh standard concrete grade.
• Hence setting the grade as M30., and checking all other parameter of the concrete we can the add teh created material property.

Step 3:

• In this whole project we are going to use the above created material properties as the standard property for all the models to be created.
• Hence the material property was created.
• Now let us create the modeling elements like , beams, column and slab.
• The size of the column, beam and slab varies with each model.
• For the model A we are goin to create column size as 400x400mm, Beam as 300x400mm and slab thickness as 150mm.Initialy creating the beam.
• To create the sections go to the define option in the tool bar and then select section properties.
• In section properties we need to add the required section.
• First is beam so seelct the concrete rectangular section.And then add the sizes and add the material type in teh sections.Thus the beam is created.

• After the beams create the column section.
• By adding the new section property as concrete section.
• And setting up teh required column size for the model A.
• And adding the required material for the section.
• Thus the column is created. 

• To create slab section we need select define option as did before and section properties in that slab sections.
• And selecting slab section we need to add property and name the section as S150 and edit the section property 
• And provide modeling type as membrane.then input the required slab thickness.
• Thus the slab is created.The created slab is to be used in all the models in this project.

• The creating load patterns will be used in the rest of the models in the project.Add wall load, EQX and EQY.
• Other loads like Live load and Dead loads preexists in the software o we can add according to our requirement.
• EQX and EQY are assumed to be seismic loads and the load pattern reference is set to IS1893:2016.
• thus load pattern is shown below

• After setting up teh lload pattern we need to set up mass source.
• In mass source we are setting up load multplier of the load pattern created. 
• Thus created mass source is shown below.

• Hence the pre modelling settings are done and teh modelling of teh structural model can be stared.
• Now the model is started by placing the elements.Column sections are placed on the required grid points and the beams are placed on the  grid lines .
• Both the columns and beams are placed by using quick draw tool.Thus the placed model is shown below. 

• Asign slab fot the structure ,select the similer story option because we dont want slab at plinth level 
• click on Set plan View ,select Story 1 
• Click on APPLY and OK

• Then go to the Quick Draw Slab Option ,properties dialogbox is open .From that select S150 

 

• Assign Loads for the structure,so that Go To The Select Option 
• Click on Properties ,select the Frame section 
• Select the Beam Properties shown below 

• Then go to assign tab,click on Frame Loads 
• then click on Distrubited, then one dialogbox is open 
• fromthat select the load pattern as wall and give the wall load as 10 kN 

• apply 3 kN live load on slab , so that Click ON Select Option 
• then select properties and slab section 

• select it and then close it,Then go to the Assign tab 
• click on Shell Load, Then Uniform 
• A dialog box is open as shown below form that select the load pattern as Live load and give the load as 3 KN. 

 

• Assign diaphragms to calculate center of mass and rigidity of the structure is calculated . 
• so that select the all slab and go to the select tab 
• click on properties  then slab section 
• select the slab.

• then go to Assign tab and Click on Shell option 
• then Click on Diaphragms  select D1 option

• click on Apply and Then Ok 

RUN ANALYSIS :

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Model B:

Step 1:

• Now to model building B, we need not create a new ETABS file from scratch.
• Rather we will save a copy of the building A file and do the alterations needed for building B.
• we can increase the number of stories to 5 by editing the story data within the copied file. So, the complete procedure to do so in ETABS is below

Step 2:

• Increase the story of the buildig 
• Click on Edit ,edit story on grid 
• one dialogbox will be open 

Step 2:

• from this dialogbox click on,click on Modify/ Show story data 
• one new dialogbox is open , click on add story 
• add 3 more story

 Step 3:

• Checked whether load is applyed or not 
• so that click on Display Shell Load Assign , one dialogbox will be open 
• select the load pattern as live load 

• Then check the wall load, so that click on 
• Display Frame Load Assign tab and select the load pattern as wall load 

• Assign Diaphragms , so that first select the slab section 
• click on Select tab  and then properties and then slab section 
• one dialogbox will be opened click oK 

• click on Select 
• then click on Assign tab , then click on Shell and then diaphragms 
• one dialogbox will be opened then click on D1 

• Then click on APPLY And then ok 

 Run Analysis 

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Model C:

Step 1:

• The story and grid data for building c will remain still.
• we need to change the column size and orient the same in the X-direction.
• Change the column size of the building .so that , go to Define tab
• Then Section Properties , Then Frame Section one dialogbox is open 
• click on c400x400

• then click on Modify/Show Properties 
• new dialogbox is open 
• From that give the name as C550x300
• depth of column is 550 and width of column is 300

• then click okand again one dialogbox is open 
• from that click ok 

Step 2: 

• select the columns , for that go to Select tab 
• then Properties , then frame section 
• one new dialogbox is open 

• click on Select option and then close

Step 3:

• Rotate the columns at 90 degree 
• so that , Go to the assign tab then click on Frame and Then Local Axis 
• one dialogbox is open click ok

• so that first select the slab section 
• click on Select tab 
• then properties and then slab section 
• one dialogbox is open

• Selcect the slab , go to the Select tab 
• then Properties Then Slab section , click on Slab150 and then click ok 
• Select the diaphragms and go to Assign tab 
• click on shell and then diaphragms

Run Analysis:

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Model D:

Step 1:

• In this model, we don't need to change anything other than the column orientation.
• The sizes of the column will remain the same,we have to shift the column orientation from X to Y direction. 
• Click on File tab , Then click on Save As and Give the name of the file as Model D and then save it 
• Change the column to Y axis.so that , first select the column  
• click on Selct tab, then click on Properties and Frame Section 
• Then click on c550x300 and select it and then close it .

Step 2: 

• Change the direction x to Y, so that click on Assign tab 
• click on Frame and then click on Local axis 
• A dialog box is open from that change the angle 90 degree to 0 degree and click on APPLY and then ok 

Step 3:

• Select the slab first  and click on Select tab 
• Then properties and then Slab section, select the S150 and then close it. 
• Check for diaphragms and click on Assign tab 
• Then shell option and then click on diaphragms and click on Apply and then OK 

Run analysis :

 

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Model E:

Step 1:

• In this model, we need to add up 5 more storeys to our model.
• In addition, we also need to assign different column sizes on different floors.
• First save the ETABS file for building D as a new model as Model E.
• Then, edit the story data as we have done for our previous models in ETABS.
• Then, we need to add two new column sections with the required directions and assign them at appropriate floors in our model as specified.
• Add 5 more story in previous structure,so that go to the Edit option 
• click on Edit Story And Grid System and one dialogbox will be appear
• from that click on Modify Story Data option and add 5 story there shown below 

Step 2:

• Check the wall load and floor load of the structure 
• click on Display shell load assign and select the load pattern as live load 

• again click on Display Frame Load Assign and select the load pattern as wall load, Click on Apply and then OK

Step 3: 

• Change the column size as 600x600 ,so that click on Define tab 
• then Section properties and Frame section, select the c550x300 
•  click on Modify section and one dialogbox is open is shown below 
• Give the property name as c600x600 and give the depth as 600 and width as 600 

• click OK . 
• Then Add one more new column size 400 x 400, so that click on Add new proprties 
• Enter the name as c400x400 and then width of column as 400 and depth as 400

Step 4:

• Select the column only then hide the beam and floor 
• click on set view point tab and unselect the beam and floor and then click ok

Step 5:

• Select the column from floor 6 to 10. So that , click on view tab and Then click on Set Building view Limits 
• One dialogbox appears, from that select the Top story as Story 10 and base story as story 6

• Select the all columns, then click on Assign tab 
• then click on Frame and then click on Section Properties, a dialogbox appears

• select the c400x400 and then click on APPY and then ok 

Step 5:

• Then checked for diaphragms, so that select the slab first and go to the select option 
• Then click on properties and slab section and a dialog box appears.

• click on seect and then close it, then click on Assign tab 
• Then click on shell and then diaphragms, a dialog box will appear

• click on Appy and then OK 

Run Analysis:

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Model F:

Step 1:

• Hide the beams and floor, so that click on Set Display Option and just unselect the Beams and floor 
• click on Apply and then OK.

Step 2: 

• Select the columns from story 6 to 10, so that click on View tab 
• Set Building Limits then dialog box will appear 
• from that click on story as 10 story and base story as 6 story 

Step 3:

• Change the columns size as 600x600, so that select the columns 

• click on Assign tab 
• then click on Frame and then Section Properties 
• then a dialob box appear from that click on c600x600 columns 

• click on APPLY AND THEN OK .
• Then click on view tab, then click on Set Building View Limits 
• A dialog box will appear,from that select the top story as 10 story and bottom as base story

Step 4: 

• Again select the beams and floors, click on Set Display Option 
• A dialog box will appear, from that click on Beam and slab and then click ok 

Step 5: 

• Check for diaphergram, for that first select the slab 
• click on Select the tab and click on Properties 
• Then Slab section, a dialog box appear
• select the slab150

• Then click on Assign tab 
• click on Shell and the diaphergrm and click on D1

Run Analysis:

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Model G:

Step 1:

• Click on File menu and then click on Save As then file name as Model G 
• Add more 15 story and click on Edit, then click on Edit Story And Grid System Data option 
• A dialog box will appear

• from this click on Modify /Show Story data and add more 15 story 

• click ok 

Step 2:

• check the live load and wall loads of the structure 
• Check Live load and click on Display Shell Load Assign and
• select the load pattern as Live load 

• click on Apply and then OK . 

• Check wall load ,click on Display Frame Load Assign tab 
• A dialog box will appear, select the load pattern as wall load 

Step 3:

• define columns as c400x400, c600X600 and c800x800 . 
• Click on Define tab and then Frame section 
• A dialog box will appear, create a new column as c800x800

Step 4:

• Apply different size of columns for each story, so that click first hide the beams and floors of the structure . 
• click on Set Display View tab and unselect the beam and floors option 
• click on Apply and then OK .

Step 5:

• Click on assign tab and then click on Frame and then Section Properties 
• A dialog box will appear, select the c400x400

• Provide column size as 600x600 and click on View option, then click on Set Building Limits option 
• A dialog box will appear and select the top story as story 20 and bottom story as story 11.

• click on OK and then click on Assign tab 
• Then click on Frame and then Section Properties.

• again click on View Option 
• click on set building view limits

• then Make visible beam and slab of the structure, click on Set Display Views Option and select the Beam and Slab Option and then click OK.

Step 6:

• select the slab click on Select tab 
• then again click on Select and then properties , next is slab section 
• A dialog box will appear ,click on Slab150

• click on Select and then closed it, click on Assign tab, select Shell and then Diaphragms 
• A dialog box will appear, from that select D1

• click on APPLY and the OK

Run Analysis:

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Model H:

Step1:

• First click on File option , then click on Save as and Give the file name as Model H and the save it 

Step 2:

• First hide the Beam and floor and the click on APPLY and the OK 

Step 3:

• Assign all columns as 800x800, so that first select the columns

• Click on Assign tab, then click on Frame and then section properties 
• A dialog box will appear, From that select c800x800

Step 4:

• Select the beam and slab and click on set display option 
• Then select the beam , floor and diaphragms option 

Run Analysis:

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Model J:

Step 1:

• Select all the slab and click on Select tab 
• Then click on select tab then section properties and slab section 
• A dialig box will appear, from that click on Slab150
• then click on Select and then close 

Step 2:

• Increase the 10 % of live load and click on Assign tab 
• then shell load, then click on Unifom 
• A dialog box will appear and give the load as 3.3

Run Analysis:

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Model K:

Step 1:

• Click on File tab then click on Save as give the file name as Model K 
• And then save it . 

Step 2:

• Increase the live load by 20 %, click on Select tab  and then again click on Select and then properties and then slab section .
• A dialog box will appear, select Slab150.

Step 3:

• Assign load, click on Assign tab 
• Then click on Shell load select  on Uniform 
• A dialog box will appear, from that select the load pattern as live load and then give the load 3.6.

Run Analysis:

Result:

Model A:

Model B:

Model C:

Model D:

Model E:

MOdel F:

Model G:

Model H:

Model J:

Model K:

Criteria :

• Effect of stiffness on time period for Model E (10 Story with varying column size) : 1.73 s
• Effect of stiffness on time period for Model F (10 Story with uniform column size) : 1.74 s
• Effect of stiffness on time period for Model G (25 Story with varying column size) : 3.57s
• Effect of stiffness on time period for Model H (25 Story with uniform column size) : 3.57s
• Effect of mass on time period for Model H (25 Story with 3KN/m^2 imposed load) : 3.57s
• Effect of mass on time period for Model J(25 Story with 3.3KN/m^2 imposed load) : 3.57s
• Effect of mass on time period for Model K(25 Story with 3.6KN/m^2 imposed load) : 3.58s
• Effect of column orientation on time period for Model B (All floors column size 400x400) : 1.03s
• Effect of column orientation on time period for Model C (All floors column size 550x300 in X direction orientation) : 1.14s
• Effect of column orientation on time period for Model D  (All floors column size 300x550 in Y direction orientation) : 1.12s
• Effect of flexural stiffness of structural elements on mode shape for Model B (Flexural stiffness of beams close to 0(Zero inertia) : 2.62s
• Effect of flexural stiffness of structural elements on mode shape for Model B(Flexural stiffness of beams(Regular) : 1.03s
• Effect of Axial stiffness of vertical members on mode shape for Model H (Axial cross section for columns is close to 0(Zero axial area) : 5.96s
• Effect of Axial stiffness of vertical members on mode shape for Model H (Axial cross section for columns(Regular) : 3.57s
• Effect of degree of fixity at column base on mode shape Model B (column support pinned(Regular) : 1.03s
• Effect of degree of fixity at column base on mode shape Model B (column support fixed : 0.941s

Conclusion:

• All the 10 buildings were modelled and analysed successfully.
• Suggested paramters and specifications were used.
• Analysis was run on the model using the Etabs
• And the results from the analysis was updated

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