Foundation Design using SAFE
1. Answer
Aim - Model the isolated footing provided in week 11 challenge on SAFE. Analyze and design it to verify the size, depth and steel provided as per calculations.
Procedure -
Open Safe Siftware.
New Model >Input the setting > Metric Units > IS 456 - 2000.
Now select single footing
Subgrade Modulus = FOS x SBC / Settelment.
Safe Bearing Capapcity = 150 kn/m^2.
FOS = 3.
Settelment = 50.
Subgrade Modulus = 3 x 150/0.05 = 9000 kn/m^3.
The compression axial load for the load combination of (1.5 DL + 1.5 LL)is 2000kn.
Unfactored Load = 2000/1.5 = 1333.33 kn.
1333.33/2 = 666.65 kn.
Square footing for a column size of 400x400.
The thickness of the concrete footing to be 0.8m.
Matrials needs to be added.
Define > Material Property.
Concrete M25.
Modulus of elasticity = 25x5000 = 25000 N/mm^2.
Add Rebar.
Add the slab properties.
Define > Slab Properties.
Stiff 1> Same as Slab Property.
Footing property is added as well.
Assign the loads.
Draw>Points and then assign dead load and live load.
Assign Load Combinations
Now we will have to run the analysis
As it is less than 50 mm it is exceptable.
Now add the design strip
Run the analysis and show the slab deisgn.
Slab Design
Result -
Therefore the Isolated Footing Design is Completed.
2. A column of size 600x600 carrying an unfactored gravity load (DL+LL) of 1175 KN is to be supported on pile cap, which ultimately transfers load to the piles underneath. Piles of 16 metres length and 500 mm diameter are to be used. Each pile has a load carrying capacity of 200 KN. Model, analyse and design the pile cap on SAFE to evaluate the following:
- Pile group to be used
- Depth of pile cap
- Longitudinal steel on top and bottom face in both directions
Procedure -
Column Size 600 x 600
Unfactored Load = 1175 Kn
Piles
16 m length and 500 mm Diameter
Loading Capacity 200 kn.
No of Piles = 1175 / 500 = 6
Spring Constant = EA/L = 25000 x 196349 / 16000 = 306795 N/mm
Where , A = 196349 mm^2, E = 25000 N/mm^2, l = 16000 mm
Minimum Spacing = 2.5 x Diameter
= 2.5 x 500 = 1250 mm
Edge Spacing = 200 mm
1. Open safe Software
New Model > Code IS 456 - 2000 > Minimum Cover > 50 at Top and Bottom
Bar Size 16 mm.
Select Grid Option
X directuin of Distance 2900 mm
Y Direction of Distance 1650 mm.
2. Adding the materials
3. Adding Slab Properties
4. Add the slab to the model
5. Draw Points
6. Add Piles.
Modified the edge distance to 300 mm.
Using Draw option the column is created in the centre.
7. Add Springs
Piles> Assign > Support Data > Point Springs
Spring Constant = EA/L = 25000 x 196349/ 16000 = 306795 N/mm = 306.795 Kn/mm
8. Add the loads
Dead Load = 587.5 Kn
Live Load = 587.5 Kn
9. Run the analysis
Maximum Displacement is 0.84 hence Safe.
In Case of Punching Shear All valves are less than 1
Now Reinforecement Deatiling to be done
X-Direction
Y-Direction
Run the analysis once again
Reinforcement Slab design
Result -
Completed Design for Pile Cap foundation using Safe Software.
