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

Aim :  

In this project, participants will get to experience the entire design process from modelling, analysis, design, and preparation of construction drawings. The architectural drawings of a G+3 RCC building is provided. The following information on the building is to be used:

• Location – Guwahati, Assam
• Function – Hostel block in an academic institute

The walls will be made of AAC blocks. Other loadings are to be calculated as per the architectural drawings. 

The buildings rests on type 3 soil. Piles of length 10 meters and 500 mm diameter with a load-carrying capacity of 280 KN is to be used. 

The ground floor level will be at a height of 2 meters above the existing site level to avoid floodwater enter the building.

M25 grade of concrete with Fe500 for longitudinal reinforcement and Fe 415 for shear reinforcement is to be used. 

The following design IS codes will be required for reference:

• IS 875 part 1
• IS 875 part 2
• IS 13920
• IS 1893
• IS 2911 part 2
• IS 456
• SP 34

Students will have to produce the following:

• Etabs model for the two blocks on either side of the expansion gap
• Foundation details illustrating the pile & pile cap reinforcement
• Tie beam details connecting the pile caps
• Column reinforcement
• Framing plan for typical floor
• Beam reinforcements for ground floor

PROCEDURE :

i) Open the Etabs software from deskstop icon 

ii) Once software is open - Click on New model 

i) Once you click on New model 

ii) A Model Initialization setting will open 

iii) Select - Metric SI units 

iv) Select section database - Indian 

v) Select Steel code - IS 800-2007

  

i) Once you click Okay 

ii) A following dialog box of grid settings will open 

ii) In New Model Quick templates under grid dimensions select the custom grid spacing

iii) Once you click on Custom grid spacing 

iv) Click on Display grid data as spacing 

i) Once you click on Okay 

ii) A plan and 3D view of model is created in model space 

i) Now we have to define the materia properties 

ii) Click on Define 

iii) Click on Material properties 

viii) Click on okay 

ix) The remaining data is as per IS code 

i) Similarly we have to define the materia properties for Steel 

ii) Click on Define 

iii) Click on Material properties 

iv) Click on Okay 

v) The remaining data is as per IS code 

vi) Material properties is added 

i) Now we have to Define the section properties ( Column and Beam ) 

ii) Click on Define 

iii) Select - Section properties 

iv) Click on Frame Section 

v) Click on Okay.

vi) Click on Add new property 

vii) Select Rectangular shape 

vi) Give property name - Beam 400x500............( given) 

vii) Material type - M25

viii) Section Shape - Concrete Rectangular

ix) Depth - 500 mm

x) Width - 400 mm

xi) Click on Modify / show Rebar 

xii) Select M3 Design Only (Beam) 

xiii) Select the rebar materials as HYHD Fe415 in both the direction 

xiv) Click on okay . 

xv) Similarly we have to follow the same steps for Column also.

xvi) Property name - Column 550 x 550 mm

xvii) Material - M25

xviii) Depth - 550 mm

xix) Width - 550 mm 

xx) Click on Modify / show Rebar 

Step 9) 

i) Now we have to define Slab properties

ii) Click on Define 

iii) Select Section Properties - Select Slab properties 

iv) Click on Slab Section 

v) Give property name - Slab 150

vi) Slab material - M30

i) Now we have keep the 3D view also to see the properties 

ii) Now we have to add the columns and beams 

iii) Click on Quick Draw Column option 

iv) Select the Column properties which we have defined earlier 

vii) Similarly we have to draw beams also 

viii) Select Quick Draw Beam option

ix) Select the Beam properties which we have defined earlier

x) Draw the beam as shown below 

 

i) Now we have to add the slabs 

ii) Select Quick draw floor 

iii) Draw the slabs as shown below 

i) Now we have to assign the loads 

ii) Select Define

iii) Click on load patterns 

iv) Define load pattern dialogue box will open 

v) Add the Following loads and Select the IS code for Seismic Case as IS -1893 

iv) The direction and eccentricity were selected as the X direction

v) The Response Reduction Factor R was taken as 5

vi) Seismic zone is 5 so Z=0.36 

vii) Soil type was taken as III

i) Now we have to assign the loads to the strucure - 

1) AAC block  load - 3.5 kn/m2

2) Live loads were applied to slabs next.

i) As per IS 875 in residential buildings its 2kn/m^2 for rooms and

    

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

    

i) Now we have to assign Mass source 

ii) For that Define menu-  mass sourceoptions to open the mass source dialogue box.

iii) Now select Modify mass source data option and click OK

iv) Now mass source datawas provided as shown and load patternwas also added to it.

v) For live load upto 3Kn/m2 - we have to assumed some fraction of live load i.e 25% 

Step 14) 

i) Now we haev to assign diaphragm

ii) In assign menuselect Shellfollowed by Diaphragm to open the shell Assignment diaphragm dialogue box

iii) Select D1 from the diaphragm assignments and click apply followed by OK.

i) Now we have to add the load combinations

ii) Click on Add default Design Combo 

i) Now we have to create a Modal analysis 

ii) For that define tab- modal cases- and select modify

iii) Enter the data’s as shown in image. Maximum number  as 20.

i) New function was defined as per the IS 1893 for response spectrum analysis.

ii) After selecting the response spectrum the new tab is visible,

iii) In that we choose IS 1893:2016 from the "Choose function type" and click on the Modify /Show option as shown below

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

i) Now we have to check themodel for errors,go to Analysis tab and select check model.

i) Now Run the model 

ii) Click on Run Analysis 

'

1) Modal Participation ratio - 

i) Modal number check for that go to Display-Show Tables-Analysis Results-Structure Output-Modal Information-Modal mass

    participation ratio.

ii) 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.

iii) 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.

iv) 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.

2) Storey response plot:

ii) For this go to Display-Story Response Plot- Maximum Storey drift

iii) Here storey response for maximum storey drift is less than 0.004 for both X and Y

i) Click on beam design check 

ii) Check for Beam Shear reinforcement 

iv) Column Shear Reinforcement 

Beam Reinforcement details 

 Design of Foundation - Pile foundation 

i) In order to export the ETABS model into SAFE click on file – Export – Story as SAFE V12.f2k file option

ii) Once you click on this option folowing diaog box will open 

iii) Select Story as Base

iv) Now Save the file to desired location

Given  data:-

i) Column of size:- 550mm *550 mm 

ii) pile has a load carrying capacity of 280kN

iii) Pile length-16 m and dia of pile -500 mm

iv) SBC-150kN/m^2

 v) Number of piles=Total Axial load/pile capacity=(1.5DL+1.5LL)/280= numbers

ii) Piles in the springs are defined as spring so for that the spring constant

 vi) K=EA/L

E=5000(fck)^0.5=5000(25)^0.5=25000 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

i) We can see that all the grids are exported to the safe . 

i) Now we have to assign the Material proprties 

ii) Define - Material Properties 

iii) Click on Add new materials

iii) Once you click Add new material add the following parameters

iv Material Type - Concrete 

i) In pile cap we have to define 3 slabs properties 

ii) For Pile Foting

iii) For Pile cap 

i) Once slab proerties are defined 

ii) Now we have to start the modeling 

  

i) Now we have to add Springs to the pile because it behaves like a spring 

ii) Click on Assign – Support Data – point springs 

iii) Spring Constant from above calculation is taken as

iv) Add Spring Constant 419 kn/mm

i) Check the model 

ii) And Run the analysis 

1) Check for Displacement  - 

     We found that Displacement is less than allowable settlement 

      i.e 0.8 < 25mm 

2) Check for Punching Shear - 

i) Click on Display - Punching Shear 

ii) As we can see that Punching shear is less than 1

  i.e 0.77 <1.....................................Safe

i) Now we have to add the Design srips 

ii) Click on Edit  - Add / Edit Design Strips 

iii) Add the Strips in both X and Y direction 

i) Run the model again 

ii) Click on Display - Show slab Design 

i) Column Dettail Reinforcement

ii) Beam Reinforcement