Project 1_Comparative study of different storey buildings for Seismic forces

Project - 1

Etabs

Question no.1:

Factors influencing the dynamic characteristics of a building

Factors influencing the Natural Period of a building

Factors influencing the Mode shape of oscillations

• Aim:

• To create structural models of various specification using ETABS software.
• To follow suggested specification
• Analys the structural models using ETABS software

• Procedure:

• Initially open the ETABS software.
• Then create new model file by clicking the new model tab in the software opening interface.
• After the this save the model with appropriate names.
• In this project we are going to model 10 structural models , each consisting different specifications.
• Specification change such as column size, column alignment and the no.of story in the model.
• Initially let us start the model with model A.

• MODEL A:

• In model A, we are suggested to create 2 story buidling with said column and beam sizes.
• So to creat 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

• After the creation of the grid data we need to edit teh story data.
• No 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
• Thus created story data is shown below

• Thus the story and the grid datas for the modelA is set up.
• 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.
• Thus created concreted concrete property is shown below.

• Now after this we need to create a material for reinforcement.
• In this project we are going to use rebar as HYSD415(Fe415) for the steel.
• Hence add new property for the steel.
• Thus added rebar property is shown below

• 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 selet 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.

• After the column creation we need to create a salb section.
• To create slab section we need seclect 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.

• After the slab creation we need to define the load patterns to be used in the model.
• 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 created 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.

• Then the load combination is set up.

• 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 elemens.
• 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.

\

• And then teh slab is placed by the same quick draw method.
• Thus the slab created is shown below.

• Then the created load is assigned in the model to the beams.
• To the slabs

• After the laod is being assigned we are assigning diaphragm to the slab

• Hence the model is created and the analysis of the structure is done.

• MODEL B:

• The modal B has the most of teh specification of the modal A.
• Hence the model is created as of the modal A.
• But in this model we are going to change the storey height and do teh analysis.
• Here we are increasing the story to 5 storey.
• Hence following the story edit settings as of model A the created story is shown below.

• And then with same loads and settings the analysis is run for the model B.
• The run analysis is shown below

• MODEL C:

• Following most of the specification as of the models created before.
• Here we are changin the dimensions of the columns.
• And then, as the created column dimension creates the column as rectangular column so changing the axes of the columns as required.
• Thus changed column sizes and axes are shown below.
• The axes change is 90 degrees

• Then following specification of previous models.
• With changed specifications in the model the analysis was run
• Thus the analysis is shown below.

• MODEL D:

• In this model we are just going to change axes of the columns created from the model before.
• In the previous model we changed the axes of the columns to 90degrees.
• And in this model we are making the axes of teh column back to 0 degrees.
• Thus the changed axes is shown below

• Then as like previous models diaphragm for the slabs is set and the analysis was run.

• Model E:

• In this model we are going to do certain changes like change in column size and story.
• So following the method of changing teh story numbers we are changing the story of the building to 10 story.
• And make the stories similar to story 1 as did before.

• After this process we are adding the new column size required for the mdol.
• We are going to create newly 600x600 column size where 400x400 is the column size we are currently using.
• Here bottom 5 stories are going to have 600x600 column sizes.
• And the remaining top stories are going to have 400x400 size columns.
• So teh column size of 600x600 is created.

• So now we are going to place the column size in the model.
• For that , as there is 400x400 column present in all teh stories we need to change the column size only is the bottom 5 stories columns.
• For that we need to go to the view tab.
• And edit the visibilty of the story setting to bottom stroey to 5th story.

• And then in the viewelemets tab we need to offf the beam and slabs.
• And then select teh bottom 5 story.
• And then columns gets selected.
• now we need to set teh new column section with dimension 600x600.
• Now after the chane we can see teh chjange in teh column names.

• Now teh vissbility setting are reset.
• And teh by the same way we need to set teh diaphragm.
• And continue to analysis.

• MODEL F:

• In thsi model we are doing some changes.
• The story of the building is increased.
• Additional 15 stories are added to teh model.
• By following the same method followed in the previous models.

• Now all the column sizes in the entire model is changed.
• The dimension of teh column is changed to 600x600.

• And teh by the same way we are running teh analysis for teh altered model.

• MODEL G:

• In this model G we are doing a change.
• By addidng different column sizes alonhg the stories
• Additionally 800x800 columns are added to teh model.
• Bottom 10 stories are set with 800x800 column size.
• And from 11 to 20 we are adding 600x600 section columns.

• And then for teh last stories 20 to 25 we are adding 400x400 columns.

• After the changes being done.
• The analysis process is takes as like the previous models.
• Thus the analysis image is shown below.

• MODEL H:

• In this model the change is going to be less.
• Here we are going to change the column dimension to all teh story.
• The model's complete columns are changed to 800x800

• After this the model is set for analysis

• MODEL I:

• In this model we are just going to add 10% of the existing imposed load.
• That we created for the model A and followed for the models till Model H.
• 3KN/m^2 was our existing load adn increased to 3.3 KN/m^2.

• And following all the other specifications of the model.
• the analysis is done.

• MODEL J:

• This model is same as Model I.
• the change is going to be increament of load to 20%.
• Thus 3.3Kn/m^2 is changed to 3.6KN/m^2.
• And teh remainaing specification is going to be the same.
• And teh analysis is done.

• Final Analysis results of the model:

• Criteria:

• Effect of stiffness on time period for Building E (10 Story with varying column size) : 1.81 s
• Effect of stiffness on time period for Building F (10 Story with uniform column size) : 1.81 s
• Effect of stiffness on time period for Building G (25 Story with varying column size) : 4.17s
• Effect of stiffness on time period for Building H (25 Story with uniform column size) : 4.41s
• Effect of mass on time period for Building H (25 Story with 3KN/m^2 imposed load) : 4.41s
• Effect of mass on time period for Building I (25 Story with 3.3KN/m^2 imposed load) : 4.42s
• Effect of mass on time period for Building J(25 Story with 3.6KN/m^2 imposed load) : 4.43s
• Effect of column orientation on time period for Building B (All floors column size 400x400) : 1.03s
• Effect of column orientation on time period for Building C (All floors column size 550x300 in X direction orientation) : 1.14s
• Effect of column orientation on time period for Building D (All floors column size 300x550 in Y direction orientation) : 1.12s
• Effect of flexural stiffness of structural elements on mode shape for Building B (Flexural stiffness of beams close to 0(Zero inertia) : 2.62s
• Effect of flexural stiffness of structural elements on mode shape for Building B (Flexural stiffness of beams(Regular) : 1.03s
• Effect of Axial stiffness of vertical members on mode shape for Building H (Axial cross section for columns is close to 0(Zero axial area) : 5.99s
• Effect of Axial stiffness of vertical members on mode shape for Building H (Axial cross section for columns(Regular) : 4.41s
• Effect of degree of fixity at column base on mode shape Building B (column support pinned(Regular) : 1.03s
• Effect of degree of fixity at column base on mode shape Building B (column support fixed : 0.941s

• Result:

• The model was created.
• Suggested paramters and specifications were used.
• Analysis was run on the model using the Etabs
• And the results from the analysis was updated