Foundation Design using SAFE
Aim: To know the general design procedure of spread footing and pile foundation with safe software
Procedure:
Step 1:
Required data from the week 11 challenge
Square footing of column size of 400x400
Compression axial load of combination (1.5DL + 1.5LL) is 2000KN
Unfactored load = 2000/1.5 = 1333.3 KN
Dead load breakup = 1333.3/2 = 666.7 KN
Live load breakup = 1333.3/2 = 666.7 KN
The S.B.C is = 150 KN/m^2
Assume M25 concrete
Now,
Sub grade modulus for the soil = safe bearing capacity x factor to ultimate / maximum settlement
= 150 x 3 /0.05
= k = 9000KN/M^3
Rebar yield strength (fy) = 500 N/mm^2
Rebar ultimate strength (fu) = 575 N/mm^2
Elastic modulus of m25 concrete = 25000N/mm^2
Step2:
Now open the safe software
Define the properties
File > new model
Give size of the footing as per least challenge
Define > material property > concrete M25
Define > material property > rebar fe 500
Define > section property > slab section> mat > M25 > thickness 300 mm
Define > section property > slab section > footing 800mm
Define > load pattern > soil surcharge
Define > load combination
Step 3:
Now to assign the loads
Select the object > assign > joint load > assign dead load & live load
Select the object > assign > shall load > soil surcharge
Step 4:
To check the model for any error and warning and run it
Now we need to check the result
- Save bearing capacity under service load
Display soil pressure > service soil settliement
Allowable SBC is less capacity [ok]
2. Settlement under service load
Show deform shape > comb > settlement > apply
3. Two way shear check ( punching shear check )
Display > show punching shear design
4. Ultimate bending moment
Show strip forces > moment and > shear
5. Flexural reinforcement design
Show slab design > apply
2):
Design of pile footing using safe software
Step 1 :
Given data
Unfactored load = 1175 KN
Dead load breackup = 587.5 KN
Live load breackup = 587.5 KN
Point spring of pile = A x E/L
A = (pi/4)*d^2
E = 5000*fck
L = 16000
196349 x 25000 /16000 = 306796 KN/m
Safe analysis k = 306.8 KN/mm
Rebar yield strength fy = 500 N/mm2
Rebar ultimate strength fu = 575 N/mm2
Elastic modulus of M25 concrete = 25000 N/mm2
Step 2:
Data required
Number of pile required = unfactored load with self weight addition / individual pile capacity
= 1175 x 1.1 / 200 = 6.5
For symmetric placement of pile cap consider 8 piles
Center to center distance between pile cap is 3 x pile diameter ( 1500mm)
Edge distance from pile meter = 1 x pile diameter ( 500mm)
Step 3:
Open the safe software and to define the material property
File > new model > set the no of grid and distance
Define > material property > add new material M25 concrete
Define > material property > add new material > fe 500
Define > slab section > slab property > add new property as pile_cap
Define > slab section > slab property > add new property as column
Define > slab section > slab property > add new property as pile _ 500
Step 4:
To assign load and property
From the toolbar take draw rectangle draw slab > type of slab > pile_cap
Draw > point > take the edge distance in x and y direction 450 from the point ctc as 1500mm
Toobar > draw area around the point > select type pile 500 and column 600
Assign > select the point > joint > spring > assign
Select the point > assign > joint load > give load 587.5 as dead and live and apply
Step 5:
To check the model for any error and warning and run it
Now we need to check the result
- Individual pile capacity under service load
2. Settlement under service load
3. Punching shear check
4. Flexural reinforcement design for footing slab
