Foundation Design using SAFE

1.Ans.

AIM:

• To analyse and design the isolated footing from week 11 on SAFE
• To verify the size,depth and steel provided as per calculations.
  
  Procedure:
  
  Step1:
• Open the SAFE application.
• Select New model.
• Followed by the input settings,Units was selected as metric and code IS456:2000
  
  
  
  Single footing was selected.
  subgrade modulus = F.O.S x S.B.C/max settlement
  =(3x150)/0.05
  =9000KN/m^3
  
  The compression axial load for the load combination (1.5DL+1.5LL) is 2000KN.
  Unfactored load = 2000/1.5 = 1333.3KN
  Dead load breakup = 1333.3/2 = 666.5KN
  Live load breakup = 1333.3/2 = 666.5KN
  Therefore, Footing thickness 800mm.
  
  
  
  Step2:
• Define materials
• Add new material property,M25 concrete.
  
  
  
  
  
• Add rebar Fe500
  
  
  
  
• Material property data:
  click define > material properties
  Rebar yielding strength (Fy) = 500N/mm2
  Rebar ultimate strength (Fu) = 545N/mm2
  M25 grade of concrete
  Modulus of elasticity E= 25 x 5000=25000N/mm2
  
  Step3:
• Define slab properties
• Define properties for footing
• Define properties for Mat
  
  
  
• Define properties for Stiff
  
  
  Step4:
• Define load pattern
  
  
  Step5:
• Define soli subgrade modulus/Area spring property data
  
  Step6:
• Assign point load
  
  Step7:
• Assign load combinations
  
  
  Step8:
• Check design preference (min cover 50mm)
  
  Step9:
• Run analysis and design
  
  
  Step 10:
• Safe bearing capacity under service load is 152KN/m2
  
  
  Step11:
• Two way shear check
  
  Two-way shear is 0.719,Hence OK.
  
  Step12:
• Ultimate Bending moment and shear force check
  
  Bending moment
  
  
  
  Shear force
  
  
  Step13:
• Flexural Reinforcement design for footing slab.
  
  
  RESULT:
• The isolated footing was designed and analysed using SAFE software successfully.
• Safe bearing capacity under service load is 152KN/m2,Hence OK.
• Two-way shear is 0.79,Hence OK.
• Ultimate bending moment and shear force check done successfully.
• Flexural reinforcement design for footing slab done successfully.
  
  2.Ans.:
  
  AIM:
• To model analysis 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:
  
  Given:
  Column size = 600 x 600mm
  Unfactored load = 1175KN
  Pile length = 16m
  Pile diameter = 500mm
  Load carrying capacity = 200KN
  
  Calculations:
  No.of piles=1175/200=5.6=6
  Spring constant = EXA/L
  where,E=25000N/mm2
  A=(500)^2 = 196375mm2
  L= 16000mm
  Spring constant=25000 x 196375/16000 = 306835N/mm or 306835KN/m
  Edge spacing is taken as 200 or 300mm.
  
  Step1:
• Open SAFE application
• Select new model
• Followed by input settings,units was selected as metric and code is 456:2000
  
  
  Step2:
• Co-ordinates was defined next
• Grid spacing in X-direction and Y-direction was taken as 3.2m and 2m respectively,as shown below.
  
  
  
• Check design preference (min cover 50mm)
• 50mm each was provided as cover at top and bottom and bar size was defined as 14mm
  
  
  Step3:
• Material property data:
  Click define > materail properties > M25 grade of concrete
  Modulus of elasticity E =25x5000=25000N/mm2
  Fe500 rebar was added next as shown below.
  
  
  
  
  
• Add Rebar Fe500
  
  
  
  
  Step4:
• Define slab properties
• Define pile cap
  
  
  
• Define column
  
  
  
• Define pile_500 dia details
  
  
  Step5:
• Draw the slab by using quick draw tool > draw points
  
  
  Step6:
• Add piles at the point
• Modify the edge distance to 0.2m
  
  
  Step7:
• Create a column of 600x600mm
• Draw the column in center using quick draw tool.
  
  
  Step8:
• Spring were added
• Define spring property data,as shown below.
  
  
  
• Select pile > assign>support data > point springs
  
  
  
• Spring constant is taken from above calculation
• Dead load and live load of 587.5KN are added next.
  
  
  
  Step9:
• Load case combination was define next
  
  
  
  
  
• After defining the load combination run the analysis.
  
  
  
• Max displacement was found as shown,so its safe.
  
  
  
• Also,all the punching shear values are less than 1,so its safe.
  
  
  
  
• Joint reaction diagram,as all the reaction forces are according to the limit,so its safe.
• Reinforcement details are added next as shown in both X and Y direction.
  
  
  
  
  
  
• Run the analysis again
  
  
  Step10:
• Reinforcement slab design
  
  
  
  
• Pile cap design
• Ultimate Bending moment and shear force check.
  
  Bending Moment
  
  
  
  Shear Force
  
  
  
  RESULT:
• Complete design of pile cap foundation using SAFE software is done successfully.
• Max displacement was found as shown,so its safe.
• All the punching shear values are less than 1,so its safe.
• Ultimate Bending moment and shear force check done successfully.
• Flexural Reinforcement design for slab done successfully.