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.

Introduction 

• ETABS is an engineering software product that caters to multi strorey building analysis and design.
• SAFE represents the state of art in three dimensional finfite element technologies for structural engineering.
• Here, in this project we are carrying out the design analysis of a G+3 building situated in Guwahati,
• Assam using ETABS software and then foundation design is carried out using SAFE software

Procedure 

Step 1)

• Open the Etabs software from deskstop icon
• Once software is open - Click on New model 

 

Step 2)

• Once you click on New model
• A Model Initialization setting will open
• Select - Metric SI units
• Select section database - Indian
• Select Steel code - IS 800-2007
• Select Concrete design code - IS 456-2000

 

Step 3)

• Once you click Okay
• A following dialog box of grid settings will open
• In New Model Quick templates under grid dimensions select the custom grid spacing

• Once you click on 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
• Click on Okay.

 

Step 5)

• Once you click on Okay
• A plan and 3D view of model is created in model space

Step 6)

• Now we have to define the materia properties
• Click on Define
• Click on Material properties

 

• Add New material as Concrete
• Select Grade of conccrete -
• Standard as Indian
• Click on Okay.

 

• Click on okay
• The remaining data is as per IS Code

 

• Similarly we have to define the materia properties for Steel
• Click on Define
• Click on Material properties
• Select New material as Rebar
• Select Grade of Steel - HYHD -
• Standard as Indian
• Click on Ok

 

• Click on Okay
• The remaining data is as per IS code

 

• Material properties is added

 

Step 8)

• Now we have to Define the section properties (Column and Beam)
• Click on Define
• Select - Section properties
• Click on Frame Section

 

• Click on Okay.
• Click on Add new property
• Select Rectangular shape

 

• Give property name Beam - 400x500(given)
• Material type - M25
• Section Shape - Concrete Rectangular
• Depth - 500 mm
• Width - 400 mm

• Click on Modify / show Rebar
• Select M3 Design Only (Beam)
• Select the rebar materials as HYHD Fe415 in both the direction
• Click on okay.

 

• Similarly we have to follow the same steps for Column also.
• Property name - Column 550 x 550 mm
• Material - M25
• Depth - 550 mm
• Width - 550 mm

 

• Click on Modify / show Rebar
• Select M3 Design Only (Column)
• Select the Rebar materials as HYHD Fe415 in both the direction
• Click on okay.

 

Step 9)

• Now we have to define Slab
• Click on Define
• Select Section Properties - Select Slab properties
• Click on Slab Section
• Give property nam e- Slab 150
• Slab material - M30
• Modeling Type - Membrane
• Type - Slab
• Thickness - 150 mm

 

Step 10)

• Now we have 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 the columns at the 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
• Select Quick Draw Beam option
• Select the Beam properties which we have defined earlier
• Draw the beam as shown below

 

Step 11)

• Now we have to add the slabs
• Select Quick draw floor
• Draw the slabs as shown below

 

Step 12)

• Now we have to assign the loads
• Select Define
• Click on load patterns
• Define load pattern dialogue box will open
• Add the Following loads and Select the IS code for Seismic Case as IS -1893

 

• The direction and eccentricity were selected as the X direction
• The Response Reduction Factor R was taken as 5
• Seismic zone is 5 so Z=0.36
• Soil type was taken as III
• Importance factor for residential building with less than 200 is taken 1 and time period is taken as 0.2

 

Step 13)

• Now we have to assign the loads to the strucure -
• AAC block load - 3.5 kn/m2

 

 

• Live loads were applied to slabs next.
• As per IS 875 in residential buildings its 2kn/m^2 for rooms 

 

 

Floor Finish

• In the same way select slabs to assign floor finish which is 1 Kn/m^2

 

Step 14)

• Now we have to assign Mass source
• For that Define menu- mass sourceoptions to open the mass source dialogue box.

 

• Now select Modify mass source data option and click OK
• Now mass source datawas provided as shown and load patternwas also added to it.
• For live load upto 3kn/m2-we have to assumed some fraction of live load i.e 25%

 

Step 15)

• Now we haey to assign diaphragm
• In assign menuselect Shellfollowed by Diaphragm to open the shell Assignment diaphragm dialogue box
• Select D1 from the diaphragm assignments and click apply followed by OK.

 

• The Diaphragm D1 is applied and is as shown below.

 

Step 16)

• Now we have to add the load combinations

 

• Click on Add default Design Combo

 

Step 17)

• Now we have to create a Modal analysis 
• For that define tab-modal cases and select modify
• Enter the data's as shown in image.
• Maximum number as 20.

 

Step 18)

• New function was defined as per the IS 1893 for response spectrum analysis.
• After selecting the response spectrum the new tab is visible,
• In that we choose IS 1893:2016 from the "Choose function type" and click on the Modify /Show option as shown below

 

 

• Two load cases was defined for response spectrum analysis and set default scale factor initially

 

 

Step 19)

• Now we have to check the model for errors,go to Analysis tab and select check model.

 

Step 20)

• iNow Run the model
• Click on Run Analysis

 

Step 21)

Modal Participation ratio:-

• Modal number check for that go to Display-Show Tables-Analysis Results-Structure Output-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 firstthree 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 irrregular in mode of oscillation in two principal plan direction.
• From modal number, maximum required is 13 number as it captures more than 90% of mass in all 6 degrees of freedom.

Storey response plot:

• For this go to Display-Story 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 on beam design check

 

• Check for Beam Shear reinforcement

• Column Longitudinal Reinforcement

 

• Column Shear Reinforcement

• Beam Reinforcement details

 

• Column Reinfocement Details

 

• Design of Foundation - Pile foundation

 

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 folowing diaog box will open

 

• Select Story as Base
• Now Save the file to desired location

 

Step 2)

Given data:

• Column of size:- 550mm *550 mm ii) pile has a load carrying capacity of 280KN
• Pile length-16 m and dia of pile -500 mm
• SBC-150kN/m^2

Step 3)

• Number 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=250 00 N/mm^2
• Area of pile =22/7*d^2=3.142* (500)^2/4=196375m^2
• L-10000m K=25000*0.7855/16=306835.9N/mm
• =419

• Spacing of the piles as per clause number 6.6.2 of IS 2911
• the spacing between the piles =2.5dia 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 the Material proprties
• Define - Material Properties
• Click on Add new materials

 

• Once you click Add new material add the following parameters
• Material Type-Concrete
• Grade- M25

 

 

• Simialarly add the rebar properties

 

Step 7)

• Now we have to define Slab properties
• In pile cap we have to define 3 slabs properties
• For Pile Foting
• For Column
• For Pile cap

 

 

 

Step 8)

• Once slab proerties are defined
• Now we have to start the modeling
• 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 419 kn/mm
• Select - Compression Only

 

Step 11)

• Check the model
• And Run the analysis

 

• Check for Displacement - We found that Displacement is less than allowable settlement
• i.e 0.8 25mm

 

Step 12)

• Now we have to add the Design Strips
• Click on Edit - Add/Edit Design Strips
• Add the strips in both X and Y direction

 

 

Step 13)

• Run the model again
• Click on Display - Show slab Design

 

• Similarly in B direction

 

Results:-

• G+3 hostel was designed and analysed in ETABS
• Foundations was designed and analysed in SAFE
• All the check are done as per IS 13920-2016

• Column Detail Reinforcement

• Beam Reinforcement

• Pile Cap Reinforcement