Foundation Design using SAFE

CHALLENGE 12:

Foundation Design using SAFE

AIM:

To Foundation Design using safe

INTRODUCTION:

The safe foundation design is a foundation design that is safe and reliable. It is a foundation design that is ideal for use in areas that are prone to earthquakes or other ground movements. The safe foundation design uses a combination of a deep foundation and a base isolation system. This combination helps to distribute the load of the building evenly and prevents the building from being damaged in the event of an earthquake.

QUESTION 1:

Model the isolated footing provided in week 11 challenge on SAFE. Analyze and design it to verify the size, depth and steel provided as per calculations.

PROCEDURE:

• Square footing for a column size of 400x400
• compression axial load for the load combination of (1.5 DL+ 1.5 LL) is 2000 KN
  The safe soil bearing capacity is 150 KN/m2 at a depth of 2 meters below E.G.L.
• Assume M25 concrete grade

Data required for SAFE Analysis & Design:

• 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

Subgrade modulus for soil Safe bearing capacity x factor to Ultimate / maximum settlement

= 150 x3/ 0.05 =k=9000 kN/m3

Rebar yield strength (Fy) = 500 N/mm2

Rebar ultimate strength (Fu) = Say 575 N/mm2

Elastic modulus of M25 concrete 25000 N/mm2

SAFE Designing:

1. Open Safe software 2023.

2. Now Open the new model.

3. Open a New model, and change the units and codes as per Indian standards.

4. After that select the footing details and mention their details.

5. Now go to the definition section and define the material properties.

6. Now define the section properties like footing Slab and stiff properties.

7. Now Define the spring properties and then Add to soil 150 with the following properties.

8. Now check the Assign loads, then go to the Display section to show the load assigned and joints.

9. Now Define the load combinations SLS and ULS note below.

10. Now check the design preferences, Go to the Design section and now click on the Concrete slab/Beam design.

11. Now check the model.

12. Run Analysis and design.

13. Now check for Settlement:

Check SLS combo, For Isolated footings maximum Settlement of 50mm.

Hence it's ok.

14.Check for Soil pressure:

For the SLC combo, The SBC of soil is 150>415KN/m2 Hence it's Okay.

15.Check for Punching shear:

Punching Shear is Less than one, hence it's okay.

16. Longitudinal reinforcement requirement:

For reinforcement requirements, design stirrups are created, Go to the Edit option, to click the add design stirrups.

17. Now run the analysis.

18. Now Go to the Display option and show the slab design.

19.Maximum rebar area for strip A

20.Maximum Rebar Area Strip B

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 the 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

PROCEDURE:

Data required for SAFE Analysis & Design

• Unfactored load = 11 75 kN.
  Dead load breakup = 1175/2= 587.5 kN
  Live load breakup = 1 175/2 = 587.5 kN
• Point spring of Pile =AXE/L
  = 196349 x 25000 / 16000= 306796 kN/m

k for SAFE analysis = 306.8 kN/mm

• Rebar yield strength (Fy)= 500 N/mm2
• Rebar ultimate strength (Fu)= Say 575 N/mm2
• Elastic modulus of M25 concrete = 25000 N/rnm2

Number of piles required Unfactored load with self weight addition / individual pile capacity

= 1175 x 1.1 /200 =6.5

consider 8 piles for symmetric placement of piles under pile cap.

Take center to center distance between piles 3 x pile diameter (1500 mm)
Edge distance from pile center 1 x pile diameter (500 mm)

Assumed pile cap depth = 500 mm

SAFE Designing:

1. Open Safe Software and open the new model to set the necessary units and Grids.

2. After that we have to define the material properties of M25 concrete and Fe 500 Grade of steel.

3. Now we have to define the slab properties.

4. After completing the properties, now we have to start the modeling. First we have to draw a pile cap with the help of a quick draw tool.

5. Now Draw the reference points and enter the piles in the modeling.

6. Now draw the All piles and columns in the modeling by using a quick draw around the point tool.

7. Now we need to assign the springs, select all points, go to assign to support data, and click point springs.

8. Now we have to assign the all loads.

9. Now check the design preferences.

10. Now we have to add load combinations.

11. Now Run the analysis.

Checking for Displacements:

settlement 24mm <25mm, Hence its okay.

Checking For Punching Shear:

Punching Shear value < 1, Hence it's okay.

Checking For Joint reactions:

The Joint loads are within the limit, Hence it's okay.

12. Now we have to add the Design stirrups.

13. Now Run the model.

14. Now Select the Slab Design.

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