Foundation Design using SAFE
FOUNDATION DESIGN USING SAFE
QUESTION-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.
ANSWER:
AIM:
To analyse and model isolated footing as per calculations by using SAFE.
INTRODUCTION:
- CSI SAFE (Slab Analysis by the Finite Element Method) is the best tool for designing concrete slabs and foundations.
- SAFE provide easiness to engineer towards the safe design of structures with powerful tools like draw, analyse, design and detailing etc.
- Laying out models is quick and efficient way with the user-friendly drawing tools or user can import model from AUTOCAD or loading conditions from other software’s like CSI ETABS and CSI SAP2000.
PROCEDURE:
STEP-1:
- Open the SAFE application.
- Select new model.
- Followed by input settings, units were selected as metric and code IS 456-2000
- SINGLE FOOTING was selected next,
Subgrade modulus = (FOS X SBC)/settlement = (3 x 150)/0.05 = 9000 KN/m^3
The compression axial load for the load combination (1.5DL + 1.5LL) is 2000 KN.
Unfactored load = 2000/1.5 = 1333.3 KN
1333.3/2 = 666.5 KN
Footing thickness 800 mm.
STEP-2:
- Define materials.
- Add M25 concrete.
- Add rebar Fe500.
- Material property data:
Click define followed by material properties
M25 grade of concrete
Modulus of elasticity,
E = square root (25) x 5000 = 25000 N/mm^2
STEP-3:
- Define slab properties.
- Define properties for footing.
- Define properties for mat.
- Define properties for stiff.
STEP-4:
- Define load pattern.
STEP-5:
- Define soil subgrade modulus.
STEP-6:
- Assign point load
STEP-7
- Assign load combinations
STEP-8:
- Check design preference (min cover 50 mm)
STEP-9:
- Run analysis and design
RESULT:
Hence, the isolated footing was designed and analysed in SAFE successfully.
QUESTION-2:
A column of size 600x600 carrying an unfactored gravity load (DL+LL) of 1175 KN is to be supported on pile cap, which ultimately transfers load to the piles underneath. Piles of 16 metres length and 500 mm diameter are to be used. Each pile has a load carrying capacity of 200 KN. Model, analyse 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.
ANSWER:
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.
INTRODUCTION:
- CSI SAFE (Slab Analysis by the Finite Element Method) is the best tool for designing concrete slabs and foundations.
- SAFE provide easiness to engineer towards the safe design of structures with powerful tools like draw, analyse, design and detailing etc.
- Laying out models is quick and efficient way with the user-friendly drawing tools or user can import model from AUTOCAD or loading conditions from other software’s like CSI ETABS and CSI SAP2000.
PROCEDURE:
GIVEN DATA:
Column size = 600 x 600
Unfactored load = 1175 KN
Pile length = 16 m
Pile diameter = 500 mm
Load carrying capacity = 200 KN
CALCULATIONS:
Number of pilers = 1175/200 = 5.8 = 6
Spring constant = (E X A)/L = (25000 x 3.14 x 0.25 x 500 x 500)/16000 = 306795 N/mm
Edge spacing is taken as 200 mm or 300 mm
STEP-1:
- Open the SAFE application.
- Select the new model.
- Followed by input settings, units were selected as metric and code IS 456-2000
- 50 mm each was provided as cover at top and bottom and bar size was defined as 16 mm.
STEP-2:
- Coordinates was defined next
- Grid spacing in X direction and Y direction was taken as 2.9 m and 1.65 m respectively.
- It is shown in the below figure too.
STEP-3:
Material property data:
- Click define followed by material properties
- M25 grade of concrete.
- Modulus of elasticity, E = 25000 N/mm^2
- Fe500 rebar was added next as shown below.
STEP-4 :
- Define pile cap.
- Define column.
- Define pile details.
STEP-5:
- Draw the slab by using quick draw tool.
- Draw points.
STEP-6:
- Add piles at the point
- Modify the edge distance to 0.3 m
STEP-7:
- Create a column of 600 x 600 mm
- Draw the column in centre using quick draw tool.
STEP-8:
- Springs were added.
- Select pile < assign < support data < point springs
- Springs constant is taken frame above calculation.
- Dead and live load of 587.5 KN are added next.
STEP-9:
- Load case combination was defined next.
- After defining the load combination run the analysis.
- Also, all the punching shear values are less than 1, so it is safe.
- As all the reaction forces are according to the limit, so it is safe.
- Reinforcement details are added next and run the analysis again.
RESULT:
Complete design of pile cap foundation using SAFE software.