Foundation Design using SAFE
Foundation design using safe
1. Model the isolated footing provided in week 11 challenge on safe analyze her design it to verify the size depth and still provided as per calculations.
Aim:
- To analyze and design the isolated footing from week 11 challenge on safe.
- To verify the size depth and steel provided as per calculations.
Introduction:
- CSI safe slab analysis by the finite element method this is the best tool for designing concrete slabs and foundation.
- Safe provide easiness to engineer towards the safe design of structure with powerful tools like draw analyze design and detailing etc.
- Laying out models is quick and effect efficient way with the user friendly drawings tools or user can import model from Autocad or landing conditions from other softwares like CSI etab and CSI SAP 2000.
Procedure:
Step1:-
- Open the safe application.
- Select new model.
- Followed by the input settings units was selected as metric and code is 456-2000.
Single footing was seleceted
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 is 800 mm.
Step2:-
- Define materials.
- Add new materials property M25 concrete concrete.
- Add rebar Fe500.
- Material Property data
Click define> material properties.
Rebar yielding strength (fy)=500N/mm^2
Rebar ultimate strength (Fu)=545N/mm^2
M25 grade of concrete
Modulus of Elasticity
E= 25x5000=25000N/mm^2
Step3:-
- Define slap properties.
- Define properties of footing.
- Define properties of mat.
- Define properties for stiff.
Step4:-
- Define load pattern.
Step5:-
- Define soil 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.
Step10:-
- Safe bearing capacity under service load is 152 KN/m2.
Step11:-
- Two way shear check.
Two ways here is 0.719, hence ok.
Step12:
- Ultimate bending movement and share first check.
Bending moment.
Shear force
Step13:-
- Flexural reinforcement design for footing slab.
Result:
- The isolated footing was designed and analyzed using safe software successfully.
- Safe bearing capacity under service load is 152KN /m2 hence ok.
- Two-way is 0.79 hence ok
- Ultimate bending moment and sheer force check done successfully
- Flexural reinforcement design for footing slab done successfully.
2. A column of size 600X600 carrying an unfactored gravity load (DL+LL) of 1175 kilonewton is to be supported on pile cap with ultimately transfers load to the pile underneath 16 meters length and 500 mm diameter are to be used. Each pile has a load carrying capacity of 200 kilonewton.Model analyze and design the pile cap of safe to evaluate the following:
- Pile group to be used.
- Depth of pile cap.
- Longitudinal steel on top and bottom face in both directions.
Note: participants must refer to IS 2911 (part 2) and SP34 for 2nd challenge.
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 =600x600mm
Unfactored load =1175KN
Pile length =16m
Load carrying capacity =200KN
Calculations:
Number of pilers =1175/200=5.6=6
Spring constant =ExA/L
Where, E =25000 N/mm2
A =(3.14/4)(500)^2=196375mm^2
L= 16000mm
Spring constant=25000x196375/16000=306835N/mm or 306835kN/m
Edge spacing is taken as 200 or 300mm.
Step1:-
- Open the safe application.
- Select the new model.
- Followed by the input settings units was selected as metric and code is 456-2000.
Step2:-
- Coordinates was defined next.
- Grid spacing in X direction and y direction was taken as 3.20 meters and 2.0 meters respectively at zone 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 properties data:
Click define material properties M25 grade of concrete.
modulus of elasticity
E=25x5000=25000N/mm^2
Fe 500 rebar was added next as shown below.
- Add rebar Fe500.
Step4:-
- Define slap 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 age distance 0.2 meters.
Step7:-
- Create column of 600 x 600 mm.
- 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.
- Springs constant is taken from above calculations.
- Dead Load and live load of 587.5 kilonewton are added next.
Step9:-
- Load case combination was define next.
- After defining the load combination run the analysis.
- Max displacement was found at shown so its safe.
- Also all the punching shear values are less the 1, So it's safe.
- Joint reaction diagram as all the reaction forces are according to the limit so it's safe.
- Reinforcement details are added next as shown in the both X and Y direction.
- Run the analysis again.
Step10:-
- Pile cap foundation design or.
- Ultimate bending moment and shear force check.
Banding 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 share values are less the 1, So it's safe.
- Ultimate bending moment and cheer for check done successfully.
- Flexural reinforcement design for slab done successfully.