Foundation Design using SAFE

1. 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.

AIM:-

To model the isolated footing in week 11 challenge on safe and also to analyse and design it to verify the size, depth and steel provided as per calculations.

PROCEDURE:-

• Open safe software.
• New model> input the setting> metric unit > IS 456-2000

• Now select single footing.
• Subgrade modulus = FOS x SBC / settlement
• Safe bearing capacity = 150 KN/m^2
• FOS=3
• Settlement = 50 mm
• 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

• Materials need to be added.
• Define > material property
• Concrete M25
• Modulus of elasticity= sqrt 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.

• Soil properties.
• Define > soil properties.

• Assign
• We will have to assign the soil property.

• Right-click on the footing to get the properties.

• Assign the loads.
• Draw > points and then assign dead load and live load.

• Right click to check the properties.

• Assign load combinations.

• Now we will have to run the analysis.
• As it is less than 50mm it is exceptable.

• Now add the design strip.
• Run the analysis and show the slab design.

• Slab design:

RESULT:-

Isolated footing has been designed using SAFE software.

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

AIM:-

To design the pile cap on safe and to evaluate pile group to be used, depth of the pile cap and longitudinal steel on top and bottom face in both directions.

PROCEDURE:-

• Column size 600x600
• Unfactored load = 1175 KN ( Ultimately transfers load to the piles underneath)
• Piles:
• 16 m length
• 500 mm dia
• Loading capacity = 200KN
• No of piles = 1175/200 = 5.8 = 6
• Spring constant = EA/L = 25000x196349/16000 = 306795 N/mm
• where, E = 25000 N/mm^2
• A = ^/4 x 500^2 = 196349 mm^2
• l = 16000 mm
• Minimum spacing = 2.5 x diameter = 2.5 x 500 = 1250mm
• Edge spacing = 200mm

• Open safe software
• New model > code IS 456:2000 > minimum cover 50 at top and bottom.
• Bar size 16mm.

• Select the grid option.
• X-direction of distance 2900 mm = 2.9 m + 1250 + 1250 + 200
• Y-direction of distance 1650 mm = 1.65 m = 200+1250+200

• Adding the materials

• Slab properties

• Add the slabs to the model

• Draw points

• Add piles
• Modify the edge distance to 300 mm

• Using draw option the column is created in the centre.

• Add springs
• Piles>assign>support data>point springs
• Spring constant = EA/L = 25000x196349/16000 = 306795 N/mm = 306.795 KN/mm

• Now the load are added.
• Dead load = 587.5 KN
• Live load = 587.5 KN

• Run the analysis.

• Maximum displacement is 0.84 hence safe.

• In case of punching shear all values are less than 1 hence safe.

• Reaction forces are according to the limit hence safe.
• Now reinforcement detailing needs to be done.
• X-direction:

• Y-direction:

• Run the analysis once again.
• Reinforcement slab design.

RESULT:-

Design of pile cap foundation using safe has been completed.