Project 2_Design & Analysis of a Hostel building at Guwahati, Assam

AIM : To carryout modelling,analysis,design and preparation of construction drawings of a G+3 RCC building situated in Guwahati Assam.

PROCEDURE :

STEP 1 :

• Open the ETABS software from desktop icon.
• Once software is open - click on New model.
  
  
  STEP 2 :
• A model initialization setting will open.
• Select - Metric SI units
• Select section database - Indian
• Seleact steel code - IS800:2007
• Select concrete design code - IS456:2000 and click OK
  
  
  STEP 3 :
• In new model Quick templates under grid dimensions select the custom grid spacing.
  
  
  
• Click on display grid data as spacing
  
  
  
• Now input the storey details
• As given in question and story 1 was selected as the Master story and click on OK
  
  
  
  STEP 4 :
• A plan and 3D view of model is created in model space.
  
  STEP 5 :
• Now click on Define
• Click on material properties
• Define properties for concrete and steel
  
  
  
  
  
  STEP 6 :
• Now we have to define section properties ( column and beam )
• Click on Define
• Select - section properties
• Click on frame section
• Click on add new property
• select rectangular shape
• Give property name Beam - 400 x 500 (given) and then put all the values as shown in table.
• Click on modify / show rebar and put the values as shown in table.
• Similarly same steps for column also.Add column size - 550 x 550mm
  
  
  
  
  
  
  
  STEP 7 :
• Now we have to define slab
• Click on Define > slab properties > slab section
• Add thickness 150mm
  
  
  STEP 8 :
• Now we have to keep the 3D view also to see the properties.
• Now we have to add the columns and beams
• Click on Quick Draw column option
• Select the column properties which we have defined earlier
• Draw columns at grids as shown in below
• Note that - all stories option should be selected which is at the bottom.
• Similarly we have to draw beams also.
  
  
  STEP 9 :
• Now we have to add slabs
• Select Quick draw floor
• Draw the slabs as shown below.
  
  
  STEP 10 :
• Now we have to assign loads
• Define > load patterns
• Define load pattern dialogue box will open
• Add the following loads and select the IS code for Seismic code as IS-1893
  
  
  
• The direction and eccentricity were selected as the X-direction
• The response reduction factor R was taken as 5
• Put all values as shown in following table
  
  
  STEP 11 :
• Now we have to assign the loads to the structure
• AAC block load - 3.5 KN/m2
  
  
  
• Live loads were applied to slabs next.
• As per IS 875 in residential buildings its 2KN/m2 for rooms
  
  
  
  FLOOR FINISH
• In the same way select slabs to assign floor finish which is 1KN/m2
  
  STEP 12 :
• Now we have to assign Mass source
• For that Define menu - mass source options to open the mass source dialogue box
  
  
  
• Now select Modify mass source data option and click OK.
• Now mass source data was provided as shown and load pattern was also added to it.
• For live load upto 3KN/m2 - we have to assume some fraction at live load i.e.25%
  
  
  STEP 13 :
• Now we have to assign diaphragm
• Assign > shell > diaphragm then one dialogue box will open
• Select D1 from diaphragm assignments and click OK.
  
  
  
  STEP 14 :
• Now we have to add the load combinations
• Click on Add default Design combo
  
  
  
  STEP 15 :
• Now we have to create a Modal analysis
• For that , define > modal cases > modify
• Enter the data as shown in image.
  
  
  STEP 16:
• New function was defined as per the IS1893 for response spectrum analysis.
• After selecting the response spectrum , new tab is visible.
• In that,we choose IS1893:2016 from the "Choose function type"and click on the Modify/Show option as shown below.
  
  
  
  
• Two load cases were defined for response spectrum analysis and set default scale factor initially.
  
  
  
  STEP 17:
• Now we have to check the model for errors,Go to analysis tab and select check model.
  
  
  STEP 18:
• Now Run the model
• Click on Run analysis
  
  
  STEP 19:
  MODAL PARTICIPATION RATIO :
• Modal number check for that go to Display > show tables > analysis results > structure o/p > modal information > modal mass participation ratio.
• According to IS 1873 clause 7.1, the natural period corresponding to fundamental torsional mode of oscillation should not be greater than sum of two fundamental translational mode of oscillation (Tx+Ty>Txy) - from table 0.789 + 0.749 = 1.534 >0.745.Hence no torsional irregularity.
• IS 1873 clause 7.1(table 6),the first three modes contribution should be more than 65% of mass participation factor in each principal plan direction.Here it is 0.71 > 0.65
• Here Tx = 0.789 and Ty = 0.749,differ by 4% hence conclude that building is irregular in mode of oscillation in two principal plan direction.
• From modal number,maximum required is 13 as it captures more than 90% of mass in all 6 degrees of freedom.
  
  STOREY RESPONSE PLOT:
• For this,go to Display > storey response plot > maximum storey drift
• Here storey response for maximum storey drift is less than 0.004 for both X and Y
  
  
  
  
• Beam design check
  
  
  
• Click for beam shear reinforcement
• Column longitudinal reinforcement
  
  
• Column shear reinforcement
• Beam reinforcement details
  
  
  
• Column reinforcment details
  
  
  STEP 1:
• In order to export the ETABS model into SAFE,click on file > export >story as SAFE V12.f2k file option.
• Once you click on this option following dialogue box will open
  
  
• Select story as Base
• Now save the file to desired location.
  
  
  STEP 2:
  Given data :
• Column of size : 550 x 550mm ii)pile has a load carrying capacity of 280KN
• Pile length - 16m and dia.of pile - 500mm
• SBC - 150KN/m2
  
  STEP 3:
• No.of piles = Total axial load/pile capacity = (1.5DL+1.5LL)/280=numbers
• Piles in the springs are defined as spring so for that the spring constant
  
  STEP 4:
• k=EA/L
  
• E=5000(fck)^0.5 = 5000(25)^0.5 = 3.142*(500)^2/4 = 196375m2
• L-10000M
  k= 25000*0.7855/16 = 306835.9N/mm
• Spacing of the piles as per clause number 6.6.2 of IS 2911
• Spacing between the piles = 2.5 dia.of the piles = 2.5*500 = 1250mm
  
  STEP 5:
• We can see that all the grids are exported to the safe.
  
  STEP 6:
• Now we have to assign Material properties.
• Define > material properties
• Click on add new properties and then add following parameters as shown in image.
  
  
  
  
  
• Similarly add the rebar properties
  
  
  
  STEP 7:
• Now we have to define slab properties
• In pile cap,we have to define 3 slab properties (for pile footing,for column and for pile cap)
  
  
  
  STEP 8:
• Now we have to start the modelling
• Select Quick draw slab options
  
  STEP 9:
• Now we have to add springs to the pile because it behaves like a spring.
• Click on assign > support data > point springs
• Spring constant from above calculation is taken as
• Add spring constant 419KN/mm
• Select - compression only
  
  STEP 10:
• Check the model
• And Run the analysis
  
  
  
• Check for displacement - we found that displacement is less than allowable settlement i.e.0.825m
  
  
  STEP 11:
• Now we have to add the design strips
• Click on Edit > Add/edit design strps
• Add the strips in both X and Y direction
  
  
  
  STEP 12:
• Run the analysis again
• Click on Display > show slab design
  
  
  
• Similarly in B direction