Project 1_Comparative study of different storey buildings for Seismic forces

Project 1 on _

Comparative study of different storey buildings for Seismic forces

Factors influencing the dynamic characteristics of a building

Answer:-

• Buildings oscilate during the earthquake shaking. The oscilation causes the inertia force to be induced in the building.
• The intensity and the duration of the oscilation , and the amount of the inertia force induced in the building depends on the features of the buildings, called their dynamic charecteristics. In addition to this charecteristics of the earthquake shaking  (beyond the control of an engineer) itself.
• The important dynamic characteristic of buildings are modes of oscillation and damping ( assumed costant in most of the cases). A mode of the oscillation of a building is defined by associated Natural Period and Deformed Shape in which it oscillates.
• Every building has a number of the natural frequencies (how many?), at which it offers minimum resistance to shaking induced by the external effects (like earthquake and wind) and internal effects (like motors fixed on it).
• Each of these natural frequencies and the associated deformation shape of a building constitute a Natural Mode of Oscillation.
• The mode of scillation with the smallest natural frequency and (Largest natural period) is called the Fundamental Mode; the associated natural period T1 is called the Fundamental Natural Period.
• Regular buildings held at their base from translation in the three directions, have two fundamental translational  natural periods, Tx1 and Ty1, associated with its horizontal translatonal oscillation along the X and Y directions, respectively, and funadamental rotational natural period T (theta 1) associated with its rotation about an axis parallel to Z-axis.

Factors influencing the Natural Period of a building

Answer:-

• Effect of stiffness on T: Compare fundamental natural periods of buildings E and F as well as G and H. Why is there a marginal of significant difference in the fundamental natural periods?
• Effect of mass on T: Compare fundamental natural periods of buildings H,J and K. Have the buildings become more flexible of stiff due to change in mass ?
• Effect of building height on T: How does the fundamental natural periods of Buildings A,B,F and H change in building height?
• Effect of column orientation on T: How does the fundamental natural periods of buildings B,c and D change with change in column orientation?

Factors influencing the Mode shape of oscillations

Answer:-

• Mode shae of the oscillation associated with a natural period of a building  is the deformed shape of the building when shaken at the natural period. Hence, a building has a many mode shapes as the number of natural periods.
• For a building, there are number of infinite natural period. But, in the mathematical modeling of building, usually the building is discretized into a number of elements. The junction of these elements are called nodes. Each node is free to translate in all the three cartesian directions and rotate about the three cartesian axes. Hence, if the numbers of nodes of the discretization is N, then there would be 6N modes of oscillation, and associated with these are 6N natural periods and mode shapes of oscillation.
• Effect of Flexural Stiffness of Structural Elements on mode shapes:- Compare fundamental mode shape of building B in two situations when flexural stiffness of beams relative to that of adjoining columns is  very small versus when it is large.
• Effect of the Axial Stiffness of Vertical Members on mode os shape: compare fundamental mode shape of building H in two situations when  axial cross sectional area of columns is very small versus when it is large.
• Effect of Degree of Fixity at column bases on mode shape : Compare fundamental mode shape of the building B in situation when base of the columns is pinned versus when it is fixed.

Question for modeling:

Structural Element Sizes 

• Beams : 300 × 400 mm 
• Columns : 400 × 400 mm 
• Slab : 150 mm thick 

Material Properties 

• Grade of Concrete : M30 
• Grade of Steel Reinforcement Bars : Fe 415 

Loading 

• Dead Load on beams from infill wall : 10 kN/m 
• Live load on floor : 3 kN/m2 

        (what is the seismic mass?)

Buildings are assumed to be pinned at base

Stepwise procedure :-

Stepwise Procedure:-

For Model A :

• Open ETAB software
• 
• Click > new model
• One dialogue box will open
• Fill all the details as below
• 
• Click>ok
• Again one dialogue box will open
• 
• Click> custom grid spacing
• Click > edit grid data >
• Add all the details as below
• 
• Click> OK
• 
• Click> custom story data > Edit story data
• Fill all the details in the table as below
• 
• Click >ok>ok
• Go to define >material properties
• 
• Dialogue box will open
• 
• Click >Add new material
• Again dialogue box will open
• Fill all the details as below
• 
• Click>ok
• Click >add new material
• 
• Take all details as below
• 
• Click >ok>ok
• Go to the define > section properties > frame sections
• 
• Dialogue box will open
• 
• Click> Add new property
• Dialogue box will be open
• 
• Select > rectangular option
• Again one dialogue box will open
• Fill all the details
• 
• Click > modify/show rebars
• Dialogue box will open
• 
• Click >ok>ok
• Again click > add new property
• 
• Select > rectangle
• 
• Dialogue box will open
• 
• Click> modify/show rebar
• One dialogue box will open
• 
• Click >ok>ok
• Go to define > section properties> slab section
• 
• Dialogue box will open
• click > add new property
• Give the details as below
• 
• Click>ok>ok
• Go to define> load patterns
• 
• One dialogue box will open
• Click > add new load and all details as below
• 
• Select > EQX
• 
• Click > modify lateral load
• Dialogue box will be open
• 
• Click >ok
• Again select EQY
• 
• Click > modify lateral load
• Dialogue box will be open
• 
• Click >ok
• Go to define > Mass source
• 
• Dialogue box will be open
• Click > modify/show mass source
• 
• Again dialogue box will open
• Fill all the details as below
• 
• Click >ok>ok
• Go to define tab> load cases
• 
• Dialogue box will open
• 
• Click >ok
• Go to define tab > load combination
• 
• Dialogue box will open
• Click > add default design combination
• 
• 
• Click >ok>ok
• Click quick draw column
• Select size of column as C400X400
• 
• Create all the columns
• 
• Click quick draw beams
• Select size from the property object as B300X400
• Draw all the beams
• 
• Make sure to set similar stories option ON
• Click > plan view
• Dialogue box will open
• Select > story 1
• 
• Click >ok
• Click > quick draw floors
• Select property > S150
• Create the floors
• 
• Go to select >properties>frame property
• 
• One dialogue box will open
• Select B300X400mm
• 
• Click > select>close
• Go to assign > frame load.> distribution
• 
• One dialogue box will open
• Take all the details as shown below
• 
• Click > apply > ok
• Go to select > select > properties> slab section
• 
• Dialogue box will open
• Select S150
• 
• Click > select > close
• Go to assign > shell loads > uniform
• 
• Dialogue box will open
• Give the load pattern name and all the details as below
• 
• Click > apply >ok
• 
• Go to select > select > properties> slab section
• 
• One dialogue box will open
• Select S 150
• 
• Click > select > close
• Go to the assign tab > shell > diaphragm
• 
• One dialogue box will open
• Select the D1
• 
• Click >apply > ok
• 
• Click on Run Analysis
• Choose the appropriate folder ,
• 
• Click > save (it will take some time to analyse the model, once completed analysis the deformed shape of model is visible)
• Once you complete the analysis , Deformed shape see in the moel.
• 
• For the Result :
• go to the model explorer
• click >table
• click > analytical result
• click > structure output
• click > model information
• right click on > table : model period 
• click on > show table 
• 

For the Model B:

• Go to the file
• Click > save as ,
• give the name as model b
• 
• Click > save
• In model b column and the beam size same
• So go with the edit
• Go to the Edit tab > Edit stories and grid system
• 
• One dialogue box will be open
• 
• Click > Modify/show story data
• Again one dialogue box will open
• Add 3 more stories for the model b
• For that right click on the to story
• 
• Click >add story > keep existing story with height
• One dialogue box will open
• Fill all the data as below
• 
• Click > ok (it will take some time to add remaining stories)
• 
• Click > Refresh view>ok
• >refresh view>ok
• Check the floor loads are visible or not
• Click > show shell loads
• 
• One dialogue box will open
• Take all data
• Click > apply
• Click > show frame loads
• One dialogue box will open
• Set the things as below
• 
• Click > Apply > close
• Go to the select tab > properties> slab sections
• 
• One dialogue box will open
• Select : S150
• 
• Click >select > close
• Go to assign tab > shell>diaphragm
• 
• One dialogue box will be open
• Select D1
• 
• Click > apply >ok
• Click > Run Analysis
• Once the analysis get completed, deformed shape shows and model is get locked
• 
• For the Result:
• go to the model explorer
• click >table
• click > analytical result
• click > structure output
• click > model information
• right click on > table : model period 
• click on > show table 
• 

For model C:

• For that I have to save the model-
• Click > file >save
• Give the file name as > model c
• 
• Click > save

Model c have a same stories as in the model b but the different column sizes , so, have to provide different column property

• Go to define tab> section properties>frame sections
• 
• One dialogue box will be open
• Set all as below
• 
• Click > modify/show property
• Again one dialogue box will be open
• Make changes as below
• 
• Click >ok>ok
• Click >save as
• Go to select tab > properties >frame sections
• 
• Dialogue box will open
• 
• Click >select > close
• We have to orient the column in the X-direction
• Go to assign tab > frame >local axis
• 
• One dialogue box will open
• Make all this as below
• 
• Click > apply > ok
• Go to select >properties>slab sections
• 
• Dialogue box will open
• Select S150
• 
• Click >select>close
• Go to assign >shell >diaphragm
• 
• Dialogue box will open
• Select D1
• 
• Click >apply >ok
• click > run Analysis
• 
• For the Result:
• go to the model explorer
• click >table
• click > analytical result
• click > structure output
• click > model information
• right click on > table : model period 
• click on > show table 
• 

For Model D:

• Click > file >save as > give name as -model d
• 
• >save
• Go to  select tab >select>properties>framed sections
• 
• Dialogue box will open
• Set all the details as below
• 
• Click > select > close
• Go to assign > frame> local axes
• 
• Dialogue box will open
• 
• Click >apply >ok
• Go to select tab > properties>slab sections
• 
• Dialogue box will open
• Select S150
• 
• Click > select >close
• Go to assign tab >shell >diaphragm
• 
• Dialogue box will open
• Select D1
• 
• Click >apply >ok
• Click > Run Analysis
• 
• once the analysis get completed , it shows the deformed shape as below
• 
• For the Result:
• go to the model explorer
• click >table
• click > analytical result
• click > structure output
• click > model information
• right click on > table : model period 
• click on > show table 
• 

For Model E:

• Go to file > save as
• Give the file name as> Model e
• 
• Click > save
• Go to the Edit tab > Edit stories and grid system
• 
• Dialogue box will open
• Click >modify/show story data
• 
• Do it as in model d
• 
• 
• 
• Click >ok
• Click >refresh view>ok>refresh view>ok
• Click > show shell load
• Dialogue box will open
• 
• Click >apply>ok
• Click > show frame load
• Dialogue box will open
• 
• Click >apply >ok
• Go to the define tab > section properties >frame section
• 
• Dialogue box will open
• Select C 550X300
• 
• Click > modify/show property
• Dialogue box will open
• Change the property as below
• 
• Click >ok
• Click >add new property
• 
• Dialogue box will open
• 
• Select > rectangular section
• Give the details as below
• 
• Click >modify/show rebar
• Dialogue box will open
• Give the details as below
• 
• Click> ok > ok >ok
• Change the visibility setting (make sure to invisible of beams and floors)
• 
• Them we able to see only columns
• 
• Go to view tab>set building view limits
• 
• Dialogue box will open
• Set the details as below
• 
• Click>ok
• 
• Select all the columns
• 
• Go to assign > frame > section properties
• 
• Dialogue box will open
• Select C400X400
• 
• Click> apply > ok (section names will be seen with columns in the model)
• 
• Go to view tab >set building view limits
• 
• Dialogue box will open
• 
• Click >show all >ok
• 
• Click >plan view option
• Dialogue box will open
• 
• Click on > story 10
• Click >apply >ok
• Go to select tab > select > properties> slab sections
• 
• Dialogue box will open
• 
• Select > S150
• Click>select > close
• Click >assign tab>shell > diaphragm
• 
• Dialogue box will open
• Select D1
• 
• Click >apply >ok
• Click >Run Analysis
• 
• For the Result:
• go to the model explorer
• click >table
• click > analytical result
• click > structure output
• click > model information
• right click on > table : model period 
• click on > show table 
• 

For Model F:

• Click >file >save as
• 
• Give the file name as – model f
• 
• Click > save
• Go to set display option
• 
• Make the beams and floors are invisible
• Go to the view tab > set building view limits
• 
• Dialogue box will open
• Set all the details as below
• 
• Click > ok
• Select all the columns
• Go to assign tab > frame > section property
• 
• Dialogue box will open
• Select C600X600
• 
• Click >apply>ok
• 
• Go to the view tab > set building view limits
• Dialogue box will open
• 
• Click >show all >ok
• 
• Make the beams and floor are visible
• 
• 
• Click > plan view option
• Dialogue box will open
• Click > apply
• Go to select tab > properties > slab sections
• 
• Dialogue box will open
• Select >S150
• 
• Click > select >close
• Go to assign > shell > diaphragm
• 
• Dialogue box will open
• Select D1
• 
• Click >apply >ok
• Click >Run Analysis
• 
• Model f is completed
• For the Result:
• go to the model explorer
• click >table
• click > analytical result
• click > structure output
• click > model information
• right click on > table : model period 
• click on > show table 
• 

For Model G:

• Click >file >save as
• 
• Give the file name as -model g
• 
• Click >save
• Go to edit>edit story and grid system
• 
• Dialogue box will open
• Click >modify/show story data
• 
• Dialogue box will open
• 
• 
• 
• Click >ok
• Click >refresh view >ok >refresh view>ok
• Click > plan view option
• Dialogue box will open
• 
• Click >apply >ok
• Click > show shell loads
• Dialogue box will open
• 
• Click > apply>ok
• Click > show frame load
• Dialogue box will open
• 
• Click > apply>ok
• Go to define tab> section > frame section
• 
• Dialogue box will open
• I want to go with the edit option
• So, select C600X600
• 
• Click>modify/show property
• Dialogue box will open
• Give the details as follows
• 
• Click >ok
• Click >add new property
• 
• 
• Dialogue box will open
• Give all the details as below
• 
• Click >modify/show rebar
• Dialogue box will open
• 
• Click >ok>ok>ok
• Make the beams and the floors are invisible
• 
• Go to vie tab > set building view limits
• 
• Dialogue box will open
• Click >ok
• 
• Select all columns
• 
• Go to assign tab >frame > section properties
• 
• Dialogue box will open
• Select C400X400
• 
• 
• Click >apply >ok
• Go to view tab >set building view limits
• 
• Dialogue box will open
  • Set details as below
  • 
  • Click >ok
  • Select all
  • Go to assign tab > section property
  • Dialogue box will open
  • Select >C600X600
  • 
  • Click >apply>ok
  • Go to view tab>set building view limits
  • 
  • Dialogue box will open
  • 
  • Click >show all>ok
  • Go to set visible option (make sure beams and floor are visible)
  • 
  • 
  • Click >plan view option
  • Click >apply
  • Go to select tab>properties>slab section
  • 
  • Dialogue box will open
  • Select S150
  • 
  • Click >select>close
  • Go to assign tab >shell >diaphragm
  • 
  • Dialogue box will open
  • Select D1
  • 
  • Click >apply >ok (when you click on extruded toggle option, column cross-section will changed)
  • Click >Run Analysis
  • 
  • Deformed shape will see in the model
  • For the Result:
  • go to the model explorer
  • click >table
  • click > analytical result
  • click > structure output
  • click > model information
  • right click on > table : model period 
  • click on > show table 
  • 

• For Model H:

  • Click >file >save as > give the file name as – model h
  • 
  • Click > save
  • 
  • Go to visibility option and make the beams and floor are not visible
  • Select all the column
  • Got to assign tab > frame > section property
  • 
  • Dialogue box will open
  • Select C800X800
  • 
  • Click > apply>ok (column sizes assigned)
  • 
  • Make sure to beams and floor are visible
  • 
  • Go to plan
  • Dialogue box will open
  • Click >apply
  • Check the visibility of diaphragm
  • Click > Run Analysis
  • 
  • Model is get completed.
  • For the Result:
  • go to the model explorer
  • click >table
  • click > analytical result
  • click > structure output
  • click > model information
  • right click on > table : model period 
  • click on > show table 
  • 

  For Model J:

  • Click > file >save as
  • Give the file name as – model j
  • 
  • Click >save

  Now here the structural changes in this model, here we have to induce 10% mass greater than that of in model h

  • Go to select tab >properties >slab section
  • 
  • Select > S150
  • 
  • Click > select > close
  • Go to assign tab > shell loads>uniform
  • 
  • Dialogue box will open
  • Take all details as below
  • 
  • Click > apply > ok
  • Click > Run Analysis
  • 
  • 
  • Model is get completed
  • For the Result:
  • go to the model explorer
  • click >table
  • click > analytical result
  • click > structure output
  • click > model information
  • right click on > table : model period 
  • click on > show table 
  • 

  For Model K:

  • Click >file > save as >give the file name as -model k
  • 
  • Click > save

  Here we have to induce mass 20% greater that the model h

  • Go to select tab > properties> slab section
  • 
  • Dialogue box will open
  • Select > S150
  • 
  • Click > select >close
  • Assign tab > shell loads> uniform
  • 
  • Dialogue box will open
  • Give the details as below
  • 
  • Click > apply > ok
  • Click >Run Analysis
  • Once the analysis completed , we will able to see the deformed shape of the model
  • Then model is get locked
  • 
  • Model is completed.
  • For the Result:
  • go to the model explorer
  • click >table
  • click > analytical result
  • click > structure output
  • click > model information
  • right click on > table : model period 
  • click on > show table 
  • 

   

 Procedure for the result of Model B- Zero Inertia:

• open Etab software
• open the-Model B
• save as -Model B zero
• 
• go to define tab > section properties>frame sections
• 
• dialogue box will open
• select > B300X400
• 
• click >modify/show property
• 
• dialogue box will open
• 
• make the changes as below
• 
• click >ok>ok>ok
• click > Run Analysis
• 
• For the result -
• go to the model explorer
• click >table
• click > analytical result
• click > structure output
• click > model information
• right click on > table : model period 
• click on > show table 
• 

Procedure for the result of Model B- changing the support as- Fixed :

• Open model B
• file > save as >MODEL B FIXED
• 
• go to plan view
• dialogue box will open
• 
• select > base
• click >apply>ok
• select all the joints
• got ot assign tab > joint > Restraints
• 
• dialogue box will open
• click on Fixed supports
• 
• click > apply>ok
• click > Run Analysis
• 
• For the Result:
• go to the model explorer
• click >table
• click > analytical result
• click > structure output
• click > model information
• right click on > table : model period 
• click on > show table 
• 

Procedure for the result of Model H-  (Zero  Axial area):

• Open Etab software
• open model-H
• go to file > save as 
• give the name as >MODEL-H ZERO
• 
• click > save
• go to define tab>section properties>frame section
• 
• dialogue box will open
• select > C800X800
• 
• click> modify/show property
• dialogue box will open
• 
• click > modify/show modifier
• again one dialogue box will open
• make changes as below 
• 
• click> ok>ok>ok
• clicl > Run Analysis
• 
• for the Result:
• go to the model explorer
• click >table
• click > analytical result
• click > structure output
• click > model information
• right click on > table : model period 
• click on > show table 
• 

Tabulated Results for all the Model :-