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

Aim:

To create the entire design process of modelling, analysis, design, and preparation of construction drawings using ETABS and SAFE software.

Overview:

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 load carrying capacity of 280 KN is to be used.

* The ground floor level will be at a height of 2 meters above existing site level to avoid flood water 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:

1. IS 875 Part 1

2. IS 875 Part 2

3. IS 13920

4. IS 1893

5. IS 2911 Part 2

6. IS 456

7. SP 34

Procedure:

Column layout:

Modeling in ETABS:

• Open the new model in ETABS software with the below settings.
• Select Custom grid spacing ->Edit grid data.
• Click ok and select Display grid data as spacing and enter the grid spacing as mentioned in the above plan.
• Select custom story data and click Edit story data and enter the details as shown below.
• Click ok then the following page appears.
• Save the model.

• Defining Material properties:
• For selecting material for rebars, Click Define-> Material properties-> Add new material.
• Select HYSD500 and HYSD415 for longitudinal and shear reinforcement respectively.

• Click ok and select new material for concrete.
• Defining Section property:
• For beam
• Click Define ->Section properties -> Frame section -> Add new property.
• Select the shape as rectangle

• Click Modify/ show modifier in property modifier and give the following details.

• Under reinforcement click Modify/ show rebar
• Select rebars for beam as shown below.

• Click ok.

• For column:
• Click add new property

• Click Modify/ show modifier in property modifier and give the following details.

• Under reinforcement click Modify/ show rebar and select the properties shown below.
• Click ok
• For slab:
• Go to Define -> Section property -> Slab section -> Add new property.
• Click ok.
• Create one way slab for stairs by using the same procedure.
• Defining load patterns:
• Go to Define-> Load patterns

• Enter additional loads and give above data and click add new load.
• Click Modify Lateral Load for all the seismic types respectively.
• For X direction:

• For Y direction:

• Defining mass source:
• Go to Define -> Mass source -> Modify/ show mass source

• Add mass multiplier for load pattern as above and click ok.
• Check the load cases:
• Go to Define -> Load cases.

• To create load combination:
• Go to Define -> Load combination ->Add default design combination.

• Combination has been created.
• To create Service load combination:
• Go to Define -> Load combination ->Add new combination.
• Modeling:
• To create Column:
• Select Quick draw column icon in the panel and select the column property type as C450X650.

• Select All stories option in the bottom right.
• Move the cursor on the grid and click to create column as shown below.

• To change the particular column orientation, select the columns to be changed and click Assign -> Frame -> Local axes -> Rotate by angle as 90.

• To create beam:
• Select Quick draw beam icon in the panel and select the beam property type as B400X500.
• Select All story option in the bottom right.
• Move the cursor on the grids lines connecting column and click to create beam as shown below.
• Create secondary beams by selecting the main beam and go to Edit -> Replicate and give the distance.
• To create slab:
• Select All stories option in the bottom right.
• Click plan icon on top of the panel and select the storey 1.
• Select Draw rectangular floor icon and select slab property type as S150.
• Connect the joints

• Select S150ow to create slab for staircase area.
• Change the orientation of the one-way slab by selecting the slabs. Go to Assign -> shell -> Local axes to 90.
• Removing unwanted elements:
• Go to plan view and have one story as option and select slabs in Base, Ground level, Mumty level and press delete.

• To assign the loads:
• Select set of particular elements and assign loads.
• Beam:
• Go to Select -> Select -> Property –> Frame section

• Select the beam type, have all story as option
• Go to Assign-> Frame loads-> Distributed.

• Go to Terrace plan view and select all beams and apply 1 KN/m UDL with one storey setup.
• Go to Mumty level and do the same for the staircase beams.

• Slabs:
• Select slab property as S150
• Go to Select -> Select -> Property –> Slab section
• Go to Assign-> Shell loads->Uniform.

• Staircase slab/ one-way slab:

• Select slab property as S150ow
• Go to Select -> Select -> Property –> Slab section
• Go to Assign-> Shell loads->Uniform.

• For Floor finish:
• Follow the above same procedure for S150

• One-way slab slab:

• Follow the above same procedure for S150ow

• To assign Diaphragm:
• Again, go to Select -> Select -> Property –> Slab section S150 and click S150ow in plan view with All stories setting.
• Select Assign -> Shell -> Diaphragms -> D1.

• Checks are to be done before running the analysis.
• All the beams and column sizes and assignments are checked

• Load pattern:

• Mass source data:

• RESULT:

• To run the analysis:
• Click Run analysis button on the top panel.

• To give moment release on a beam:
• Select the long beam and goo to Edit -> Edit frame ->Divide frame
• Select the secondary beams and go to Assign -> Frame -> Release/ Partial fixity
• Do the same procedure where ever necessary.
• To check service limit:
• Go to Reaction -> Select combination as Service.
• To check axial load on column:
• Go to any elevation view
• Click display frame icon and select combination as service and component as Axial.
• Bottom of the column has more load when compared with the top.
• Hence safe.
• To check shear force:
• With the above same setting change the component to Shear 2-2.
• To check Bending moment:
• With the above same setting change the component to Moment 3-3.

• Story drift:
• Go to Display -> Story response plot.
• Select Max story drift and EqX and EqY respectively

• Storey drift shall not exceed 0.004 times the storey height for base shear with no load factor (4x10-3).

To View Model participating mass ratio:

• Go to Display -> Show table and select the below setting.
• The sum of first-three modal participating ratio is more the 80%
• To view Model periods and frequencies:
• Select the below settings
• Torsional mode time period is less than the first- two direction time period.

Design check:

• Click concrete frame design drop down -> Verify all members passed

Exporting file to SAFE software:

• Go to Base plan view.
• Go to file -> Export -> Storey as SAFE V12.f2k file
• Select the following options with the service load combination and click ok.
• Save the file.

Modeling in SAFE:

• Go to file and open the saved file.
• Click Display joint load assigns to check the loads
• Click Reaction icon in ETABS to know the service load

Modeling Pile foundation for grid 6F:

• Here, Picking a grid 6F to model in safe. The same procedure can be followed for the remaining columns/ grid areas.

Data required for SAFE analysis and Design.

• Unfactored load = 1155.8KN
• Point spring of pile = AX E/ L =490873.75 N/mm
• A= π/4 xd2= π/4 5002 = 196349.5 mm2

• E = 5000x√fck =5000x √25 = 25000 N/mm2
• L =10M=10000mm
• Hence K = 490873.75KN/m.
• Rebar yield strength, Fy =500 N/ mm2.
• Rebar ultimate strength, Fu = 545 N/ mm2.
• Elastic modulus of M25 concrete = 25000 N/ mm2.
• Number of piles required = Unfactored load with self-weight / Individual pile capacity.
• =1155.8 X1.1 / 280 = 4.5
• Consider 6 piles for symmetric placement of piles under pile cap.
• Center to center distance between the piles = 2.5 x Pile diameter = 2.5x500= 1250 mm
• Edge distance from the pile center =1x500= 500mm.
• Assume pile cap depth = 500mm

• Column 450x650mm
• Layout of the plan:

• Defining material:
• For concrete:
• Go to Define -> Material properties -> Add new material. And enter the data in the dialog box.
• Click ok.
• For Rebar:
• Click Add new material. Add HYSD 500 and HYSD 415
• Click ok
• For slab:
• Go to Define -> Section properties -> Slab section -> Add new properties
• Repeat the same procedure to create two more slab types.

To draw pile cap:

• Select Quick draw area around point and give the dimension and click on the grid

To place points:

• Select edge point of the Pile_cap point
• Go to Edit-> Replicate and give the distance.
• Follow the same procedure to place the other points for the pile

Drawing the pile around the points:

• Select Quick draw area around the points.
• Select the following properties in the dialog box and click on the points.

To draw Stiff slab for column:

• Select Quick draw area around the points.
• Select the following properties in the dialog box and click on the points.

To draw spring in the pile:

• Go to Define -> Spring properties -> Point spring.
• Add new property with the calculated value.

• Select all 6-pile joint point, Go to Assign -> Joint -> Spring

Assigning load to the column:

• Select the column point
• Go to Assign ->Joint loads -> Force.
• Add both live and dead loads in Z direction as shown below.

Load combination:

• To add ultimate limit state and service combination, go to Define -> Load combination.

Add Design strip:

• Go to Draw -> Draw Design strip.
• Enter the value in the properties of object.
• The width can be the diameter of the pile on either side.

• Right click on the strip and change the rebar property to HYSD 500.

• To view the width, go to set view option ->other assignments -> show width.

Run the analysis:

• Click Run button to run the analysis.

Result:

• Two-way shear check (Punching shear):
• Click Display-> Punching shear design.

• It is less than 1, hence ok.
• Reaction check:
• Click Reaction icon and select combination as Service.

• Reactions are less than the pile capacity. Hence ok.

Settlement under Service load:

• Go to Display -> Show deformed shape.
• Select the combination as service.

Flexural reinforcement design for footing slab:

• Click Display -> Show slab design.
• Reinforcement details can be calculated from this.