Foundation Design using SAFE

Aim - i) To model the isolated footing provided in week 11 challenge on SAFE.

ii) To Analyze and design it to verify the size, depth and steel provided as per calculations.

iii) To model the pile cap on SAFE software .

Introduction -

1) CSI SAFE (Slab Analysis by the Finite Element Method) is the best tool for designing concrete slabs and foundations.

2) SAFE provide easiness to engineer towards the safe design of structures with powerful tools like draw, analyze, design and detailing etc.

3) Laying out models is quick and efficient way with the user-friendly drawing tools, or user can import \

model layouts from AutoCAD or loading conditions from other software’s like CSI ETABS and CSI SAP2000.

Procedure -

Step 1)

i) Open the SAFE 2020 Software .

ii) Click on New Model

Step 2)

i) Once you click on New model

ii) A following Dialog box will open .

iii) Display Units- Metric SI

iv) Select the Region Indian

v) Select the Concrete Design Code - IS 456-200

vi) Click on Okay

Step 3)

i) Once you click Okay

ii) Model Quick Template box will open

iii) Click on Single Footing - As we are designing Isolated Footing .

Step 4)

i) Enter the dimension as per calculation we have done in Week 11 challenge .

ii) As we have got Footing Size = 3.8m x 3.8m

iii) Enter the Direction Along X and Y direction as = 1.9 m

iv) Footing Slab Thicknes = 800 mm

v) For Modulus Subgrade =

we know the formula ,

Modulus of Subgrade = `(FOS X SBC )/ ( Allowab l e Set tl ement )`

i) Assume FOS = 3 as per IS 13290

ii) SBC = 150 given

iii) Allowable Settlement ( For Isolated footing ) = 0.025 m ( AS per Is 1904 )

= `(3 X 150 )/0.025`

= 9000 `(Kn )/(m^3)`

vi) Now we have to add the Load

i) For Dead load and Live load -

= (Total Unfactored load ) / 2

= `(1333.3 / 2)`

= 666.65 Kn

vi) Load Size = In that we have to enter Column Size = 400 mm

vii) Once you enter all the details Click in Okay

Step 5)

i) Once you click okay

ii) You will see the geometry is created in Model space as follows

Step 6)

i) Now we have to add Material Properties

ii) Click on Define - Material Properties

ii) Click on Add new materials

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

iv Material Type - Concrete

v) Grade - M25

vi) Click on okay .

vii) Simialarly add the Rebar Properties .

viii) Click on Okay

ix) Properties has been Define

Step 7)

i) Now we have to define Slab properties

ii) As we already define slab properties in Grid Section

iii) Clic on Modify properties - Add

iv Select the Slab Material - M25

v) Assign tje thickness = 800 mm

vi) Similarly Modify the Stiff slab

Step 8)

i) Now we have to assign Soil Properties

ii) Define - Soil Properties

iii) Right Click on slab you will see the Soil Properties has been assigned

Step 9)

i) Now we have to check if loads are defined are not .

Step 10)

i) Now we have to define the Load Combinations

ii) For that Define - Load Combinations - Either you can Add New combo or you can Add default Combo

iii) Will Add new Combo as follows

Step 11)

i) Now we can Run the model

ii) Click on Run Analysis

iii) Save the File

iv) Now you will see the Displacements

v) Click On Defotmed Shape - Select Combination as - SLS and see the displacement

vi) As displacement is -12 mm which is less than 25 mm ............Safe

2) Check for Bearing Pressure

i) For that Click On Display - Soil Pressure - Select Combination as - ULS

ii) As we can see that Bearing pressure is more than SBC

i.e 169.22kn/m2 > 150 kN/m2 ..........................Unsafe

iii) We have to Increase the area to see if we can reduce the bearing pressure below the SBC

iv) Now provide the area as 4m x 4m

v) Here we can see that after increasing the area Bearing pressure is reduced

i.e -143.30 < 150 Kn/m2..............................Safe

3) Check of Punching Shear

i) Click on Display - Punching Shear

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

i.e 0.39 <1.....................................Safe

Step 12)

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

iv) Strips has assigned

v) Command Cntrl + W to see the set display option

vi) In that tick on Strip widtht to see the Strip width

Step 13

i) Now again Run the model

ii) Click on Slab Design

iii) Select Layer A

iv) Similarly Select layer B

Results -

i) Isolated Footing is Designed for Square column of size 400mm x 400 mm

ii) We have to Provide Footing Size as 4m x 4m

iii) Bearing soil pressure is checked and found to be safe

iv) Punching shear ratio is check and found to be safe

Q.2)

Aim - To Model, analyse and design the pile cap on SAFE

Procedure -

Step 1) Given data -

i) As per IS 2911 (part 2) the spacing between the piles is taken as 2.5 times the diameter of pile

ii) The edge spacing we have assume it as 300 mm .

Step 2)

i) Open the SAFE 2020 Software .

ii) Click on New Model

Step 3)

i) Once you click on New model

ii) A following Dialog box will open .

iii) Display Units- Metric SI

iv) Select the Region Indian

v) Select the Concrete Design Code - IS 456-200

vi) Click on Okay

Step 4)

i) Once you click Okay

ii) Model Quick Template box will open

iii) Click on grid only

iv) Enter No of grids in X and Y = 2

v) Enter spacing in X = 3.1 m

vi) Enter Spacing in Y = 1.85 m

Step 5)

i) Now we have to assign the Material proprties

ii) Define - Material Properties

i) Click on Add new materials

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

iv Material Type - Concrete

v) Grade - M25

vi) Click on okay .

vii) Simialarly add the Rebar Properties .

viii) Click on Okay

ix) Properties has been Define

Step 6)

i) Now we have to define Slab properties

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

iii) Footing

iv) For Column

v) For Pile cap

Step 7)

i) Once slab proerties are defined

ii) Now we have to start the modeling

iii) Select Quick draw slab options

iv) Draw the slab select Footing as property

Step 8)

i) Now we have to mark the position of Pile cap

ii) For that we have to add the points

iii) Draw - Draw reference points

Step9)

i) Now we have to add column slab

ii) Click on Quick draw area / points

iii) Select the property

iv) and draw the columns

v) Similarly draw the pile caps

Step 10)

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 - 306795 Kn/m

v) Select - Compression Only

vi) Click on Okay

vii) Spring Constant has been assigned .

Step 11)

i) Now we have to add the loads

ii) Go to Assign - Joint loads - point force

iii) Assign 587.5 Kn dead load and 587.5 Kn live load

Step 12)

i) Now we have to add load combinations

ii) Define - Load combination

iii) Define the load combination as follows

Step 13)

i) Now Run the model

ii) Click on Run Analysis

iii) 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 0.49 <1.....................................Safe

3) Joint Reaction

i) As all the reaction forces are according to the limit, Its safe

Step 14)

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

iv) Strips has assigned

v) Command Cntrl + W to see the set display option

vi) In that tick on Strip widtht to see the Strip width

Step 13)

i) Run the model

ii) Click on slab design

iii) Select the layer A to see the reinforcement

iii) Similarly in Layer B

Results -

i) Pile Cap is Designed for Square column of size 600mm x 600 mm

ii) We have to Provide pile cap Size as 3.1m x 1.85m

iii) Bearing soil pressure is checked and found to be safe

iv) Punching shear ratio is check and found to be safe