Foundation Design using SAFE

1. Model the isolated footing provided in week 11 challenge on SAFE. Analyse and design it to verify the size, depth and steel provided as per calculations

AIM : To model isolated footing using SAFE

INTRODUCTION : Isolated footing is an individual footing used to support single column

Column size 400x400mm

Axial load = 2000/1.5 = 1333.33

Take DL = 1188.96KN , LL= 144.37KN

Soil bearing capacity = 150KN/m2

Area = 3.6x3.6m = 12.96m2

Depth = 574mm

Soil subgrade modulus = (Soil bearing capacity x FOS) / Settlement
= (150x3)/0.025
= 18000 KN/m3

PROCEDURE :

• Open CSI SAFE Software
• Open new model
• In new model initialization
  • Design code taken as IS 456 2000
  • Design preferences is taken as
    
    
    
    
• Define materials
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• Define slab properties
  • Properties of footing and column are defined
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• Define soil subgrade properties
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• Define load pattern
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• Draw footing
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• Draw column
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• Select footing and assign load (assign>support data> soil properties) : SOIL 150
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• Go to draw, select draw points and draw a point at center of footing
  
  
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• Select the point and assign loads (Assign > load data > point load)
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• Define load combination
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• Check design preferences and slab information
• Run design and analysis
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  SLS Combo result
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• Punching shear
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• Punching shear is more than 1 therefore thickness of footing changed to 575mm and run analysis

RESULTS :

• Punching shear value is 0.868
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• Draw design strips and run analysis
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2. A column of size 600x600mm carrying unfactored gravity load (DL+LL) of 1175KN is to be supported on pilecap which ultimately transfers load to piles underneath. Piles of 16m length and 500mm diameter are to be used. Each pile has a load carrying capacity of 200KN. Model, analyse and design pile cap on SAFE. Evaluating the following :

• Pile group to be used
• Depth of pile cap
• Longitudinal steel on top and bottom face in both directions

AIM : To model pile cape using SAFE

INTRODUCTION :

Axial load = 1175KN

Length of piles 16m

Diameter of pile = 500mm

Pile capacity = 200KN

No of piles = 1175/200 = 5.875 = Assume 8 piles

Area of each pile = `pi/4(d^2)` = `pi/4(500^2)` = 196349.5mm2

E = 5000`sqrtfck` = 25000

Spring constant = EA/L = (25000 x 196349.5)/16000 = 306.796KN/mm

Pile size is 500mm, therefore spacing = 2.5x500 = 1250mm, edge spacing = 500mm

Length = 5250m and Width = 2750mm

PROCEDURE :

• Open new model
• Assign IS 456 2000 in Model initialization
• Set units to metric SI
• Define materials
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• Define slab properties
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• Using reference points, draw : piles, pilecap and column
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• Select reference point of piles and assign point spring
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• Assign dead load of 1175KN at column
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• Add load combinations
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• Run analysis
• RESULTS :
• Punching shear is less than 1
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• Reactions
  
  
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• Draw designstrips
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• Run analysis
• RESULT :
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