Foundation Design using SAFE

1.

• To Analyze and design the isolated footing from week 11 challenge on SAFE

Introduction:

• CSI SAFE (slab analysis by the finite element method) is the best tool for designing concrete slabs and foundations.

Procedure:

Step:1

• Open the SAFE Application.
• Select New model.
• Followed by the input settings, Units was selected as metric & code IS 456-2000.
• Single Footing was selected.

  Subgrade modulus = F.O.S x S.B.C / max settlement

  = (3x150) / 0.05 = 9000 KN/m³

  The compression axial load for the load combination (1.5DL + 1.5LL) is 2000 KN.

  Unfactored load = 2000 / 1.5 = 1333.3 KN

  Dead load breakup= 1333.3 / 2 = 666.5 KN

  Live load breakup= 1333.3 / 2 = 666.5 KN

  Therefore, Footing thickness 800 mm.

Step:2

• Define materials
• Add new material property, M25 concrete.

• Material property data:

Click define > material properties

Rebar yielding strength(Fy) = 500 N/mm²

Rebar ultimate strength (Fu) = 545 N/mm²

M25 grade of concrete

Modulus of elasticity

E = 25x5000 = 25000 N/mm²

Step:3

• Define Slab properties.
• Define properties for footing.

Define properties for Mat.

Step:4

• Assign Point load.

Step:5

• Assign load combinations.

• Run Analysis & Design.
• Two way shear check
• Ultimate Bending moment & shear force check.

RESULT:

• The Isolated footing was designed and analyzed using SAFE software successfully.
• Safe bearing capacity under service load is 152 KN/m2, Hence OK.
• Two-way shear is 0.79, Hence OK.
• Ultimate Bending moment & shear force check done successfully.
• Flexural Reinforcement design for Footing slab done successfully.

2.

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 600 mm

Unfactored load = 1175 KN

Pile length = 16m

Pile diameter = 500 mm

Load carrying capacity = 200 KN.

Calculations.

Number of pilers = 1175 / 200 = 5.6 = 6

Spring constant = ExA / L

Where, E = 25000 N/mm²

A = [Math Processing Error](π4)(500)² = 196375 mm²

L = 16000 mm

Spring constant =25000 x 196375 / 16000=306835 N/mm or 306835 KN/m

Edge spacing is taken as 200 or 300 mm.

Step:1

• Open the SAFE Application.
• Select New model.
• Followed by input settings, units was selected as metric and code Is 456-2000.

Step:2

• Co-ordinates was defined next.
• Grid spacing in X-direction and Y-direction was taken as 3.20m and 2.0m

Step:3

• Material property data:

Click define > material properties >M25 grade of concrete.

Modulus of elasticity

E = 25x5000 = 25000 N/mm²

• Define Slab properties.
• Define pile cap
• Create a column of 600 x 600 mm
• Draw the column in center using quick draw tool.

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 the 1, So its Safe.
• Ultimate Bending moment & shear force check done successfully.
• Flexural Reinforcement design for slab done successfully.