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

PROJECT 2_DESIGN & ANALYSIS OF A HOSTEL BUILDING AT GUWAHATI, ASSAM

QUESTION:

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 Fe415 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 reinforcement for ground floor.

ANSWER:

AIM:

To create and analysis the given building in ETABS 2018, the structural model must be prepared in accordance with IS 1893 and as per IS 13920. To design the pile cap and pile reinforcement details, tie beam connecting the pile caps, to sketch the column reinforcements, to produce the framing plan and beam detailing for ground floor.

GIVEN DATA:

The wall are made of AAC blocks, pile capacity – 280 KN, M25 concrete Fe500 steel, soil type 3.

INTRODUCTION:

• ETABS is the software which is being used to create a structural model of given building.
• In the first step note down the values of grid spacing from the given structural plans.
• Next create the structural model and run the model.
• Analyse the result and note down the result values from ETABS.
• Next is to export the model to SAFE 2016 software in order to design the foundations.

PROCEDURE:

• In the first step open the ETABS software go to file and click on new model.
• Model initialisation window will be appeared.
• Click on the use built in setting and select the Indian codes and click ok.
• Now the values as per the given plans are inserted and our model will be ready.
• In the next step material must be defined. Go to define and click on material property and add the concrete and rebar material specification.
• In the next step section properties has to be defined. Go to define and click on section properties and add the beam and column specification.
• 400 mm x 600 mm beam size is provided for the all the beams.
• 400 mm x 600 mm beams are provided for the beams at periphery so as to increase the torsional resistance of the building.
• Moment of inertia for beams and columns should be reduced by 0.35% and 0.4% respectively.
• In the next step define the slab properties by going in to define and slab sections. Add the slab property as while defining the slab for staircase it should be one-way.
• Define the staircase slab and provide its thickness as 125 mm.
• Draw all the beams using beam command.
• Draw all the columns using column command.
• In the next step slabs are drawn using slabs command.
• Now we have to decide the location of shear walls and how much should be the length of the shear wall.
• As per Indian standards the length of the wall should be 0.5%-2% in each direction.
• The thickness of shear wall is assumed to be 250 mm.
• Now go to define and define the loads.
• Next select the beams and floors and add the loads.
• Next select the beams and floors and add the loads.
• AAC loads of 3.5 KN/m since the AAC blocks are used.
• The live load values are got from IS 1875 part 2 for residential buildings.
• As per clause number IS 875 part 2 reduction factor should be applied on the imposed loads.
• Live load at the roof floor needs to be reduced hence 2 KN/m is applied.
• Floor finish on all the floors 2 KN/m is applied.
• Seismic loads should be define so as per IS 1893 table no. 8 importance factor should 1.2
• Time period is calculated as per clause number 7.6.2 of IS 1893 T = 0.09 h/sqrtd, Tx = (0.09 x 16.85)/(67.7)^0.5 = 0.184 seconds or Ty = (0.09 x 16.85)/(13.3)^0.5 = 0.415 seconds.
• Now define the load combinations
• In the next step we have to define the mass source, for that go to define and click on mass source and add on the new, click on specified load data, in the mass options click on include lateral mass and lump lateral mass at story levels, in the load pattern add multiplier 0.25 for LL and 1 for all dead and super dead loads.
• And select all the floors and apply diaphragm D1.
• In the next step we have to define for the modal cases for that go to define and click on modal cases click add new model cases select eigen and put the number of modes shape required.
• Now go to define function and click on response spectrum and add new function in accordance with IS 1893-2016 check all the values click ok.
• Name the function as IS function, response spectrum IS function IS 1893-2016 tab will appear check all the values seismic zone factor soil type, importance factor click on linear x linear y click ok.
• Now go to define load cases and click on add new case and add Rsx and Rsy.
• Select the response spectrum click on add select the function as IS function and U1 for Tx and U2 for Rsy and IS function.
• Go to define click on load combination and click on default design combo, click on create frame design and click on convert to design combo click ok.
• Now check the model if there are any warning correct it and run the model.

RESULT AND DISCUSSION:

• Go to display then click show tables and then structural data click ok.
• Click on show tables, select the analysis results structure output click ok.
• Select the base reaction and check the Eqx Eqy values, Rx and Ry value see which values are larger if the Rx Ry values are lesser than the Eqx Eqy unlock the model and then go to define load case and delete the Rx Ry cases and again select the load combinations and define that again.
• Go to modal mass participation ration and check the values for U1 U2 U3 values sum of these Ux Uy Uz for the first 3 modes it should be greater than 65%.
• Go to concrete frame design and select the start design or check and note down the values of reinforcement details.
• Select modal participating ratios we have got that at mode 7 we have got above 90% so its ok.
• Now select the base reactions check that Eqx Eqy values should be same and Rsx and Rsy values also should be at least equal to Eqx Eqy respectively. If not then just take the Rsx values and divide it by Eq values whatever the values will get that values needs to be multiplied in the load cases Rsx tab.
• Check for the share of shear walls go to base level and click on reaction Ex and Ey values will be available take these values and divide it be total base shear which should be greater than 90% if now add the shear walls in appropriate directions.

IMPORTING THE SOFTWARE SAFE 2016:

• Go to file click on export and select the safe v12.fk.
• A tab will appear then click on the story as base and select the loads and loads from above click on the combination click ok.
• Go to SAFE 2016 and to file click import and select the file and save the file as FDB.
• Go to display click on the show loads select dead above and love above the values will be appeared.

GIVEN DATA:

Column of size – 400 mm x 600 mm & 600 mm x 400 mm

Pile has a load carrying capacity of 280 KN.

Pile length – 16 m and dia of pile – 500 mm

SBC – 150 KN/m^2

SOLUTION:

Number of piles = total axial load / pile capacity = (1.5 DL + 1.5 LL)/280 = numbers

Piles in the springs are defined as spring so far that the spring constant

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 = 196375 m^2

L-10000 m

K = 25000*0.7855/16 = 306835.9 N/mm

Spacing of the piles as per clause number 6.6.2 of IS 2911 the spacing between the piles = 2.5 dia of the piles = 2.5*500 = 1250 mm

• Now in the next step we have to define the material properties for go to define and define the material properties of concrete and reinforcement properties Fe500 & F2415.
• Go to define section properties and define pile caps, pile dia and column.
• Add new, defined pile cap pile500 as mat and column as stiff.
• Click on the quick draw around the plots as window will open there insert the columns sizes and these columns to their specified positions. Columns should be stated as stiff material.
• In the next step pile caps needs to be drawn for that go to quick draw slab command select pile caps and add it. Piles and pile cap should be stated as stiff material.
• Select the pile caps and changed the rebar material as Fe500.
• Next go to draw and draw point and a window will open up there draw the points where piles are to be drawn.
• Now again select the quick draw around the points there select the property circular slab add piles dia in this case 0.5 m and add to the points. Select these piles and again check for the rebar materials.
• Now we must define all the piles as spring for that go to define.
• Select soil spring properties add new property there click on compression only and add the calculation value of K=EA/l
• Select all the piles and go to assign and select support data and select spring properties and assign it.
• Go to define and select the define beam and define the tie beams whose thickness should be as of pile caps.
• Check whether the rebar material is Fe500 under design preferences.
• Go to define and select the define beam and define the tie beams whose thickness should be as of pile caps.’
• Check whether the rebar material is Fe500 under design preferences.
• Go to define and define the load combinations sls and uls.
• Go to design and design preferences.
• Save the model and design preferences.
• Save the model and run the analysis.
• Deformed shapes showed that deformations are negligible
• Assign add the design strips.
• Run the analysis.
• Deformed shape all the values are less than 25 mm hence ok.
• Now go to display and click on the punching shear the values we have go are less than 1 hence ok.
• Now go to display and select slab design.
• All the reinforcement details will be available.
• For X direction middle strip:

Maximum reinforcement was

For top : 29834 mm^2/m = 29834/3.3 = 9041 mm^2 = 28 nos. of 20 mm dia are provided.

For bottom: 13326 mm^2/m = 4038 mm^2 = 13 nos. of 20 mm dia are provided.

• For y direction:

Maximum reinforcement was

For top : 19926 = 3831 mm^2/m = 12 nos. of 20 mm dia are provided

For bottom : 22784 mm^2/m = 4398 mm^2 = 14 nos. of 20 mm dia are provided.