Foundation Design using SAFE

Que.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.

Ans

Aim:- To analyse and design isolated footing from week11 on SAFE

. To verify the size, depth and steel provided as per the calculations

Introduction:- CSI SAFE (Slab analysis by finite element method) is the best tool for desiginig concrete slabs and foundations. SAFE provide easiness to engineer towards the safe design of structure with poerful tools like draw, analyse, design and deatailing etc. Laying of model is quick and efficient way with the user friendly drawing tools, or import from AutoCAD or from other software like CSI ETABS and CSI SAP2000

Procedure:-

Step 1 :-Open SAFE application

. Select new model

. Input setting -----> Unit is to be slected as Mertic and code as IS456-2000.

Select SINGLE FOOTING

Subgrade modulus = F.O.S X S.B.C  =   3 X 150   =  9000 KN/cu.m

Settlement 0.05

The compression axial load for load calculation is  (1.5 D.L + 1.5 L.L) is 2000 KN/cu.m

Unfactored load = (2000/1.5) = 1333.3 KN

Therefore, (1333.3/2) = 666.5 KN

Footing thickness =800 mm

Step 2 :- Define material

. Add new material property

. Add M25 grade of concrete

. Material property data

. Material property design data

. Add rebar fe500

. Add new material property

. Material property data

. Material property design data

Material property data : Click on define material properties

M25 grade of concrete Modulus of elasticilty (E) = 25000N/sq.mm

Step 3 :- Define slab properties

. Define footing properties

. Define propertie 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 combination

. Step 8 :- Check deisgn prefrence (minimum cover 50 mm)

. Step 9 :- Run and anaysis design

Result :- Hence, isolated footing is designed and run successfully on SAFE.

Que.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

Ans.

Aim:- . To model, analyse and seign the pile cap on SAFE

. To evluate the following

1. Pile group to be used

2. Depth of pile cap

3. Longitudinal steel on top and bottom face in both directions

Introduction:-CSI SAFE (Slab analysis by finite element method) is the best tool for desiginig concrete slabs and foundations. SAFE provide easiness to engineer towards the safe design of structure with poerful tools like draw, analyse, design and deatailing etc. Laying of model is quick and efficient way with the user friendly drawing tools, or import from AutoCAD or from other software like CSI ETABS and CSI SAP2000

Procedure:- Given data

. Column of size 600x600

. Unfactored gravity load (DL+LL) of 1175 KN

. Piles of 16 metres length

. Piles of 500 mm diameter

. Load carrying capacity of 200 KN

Calculations 

. No.of piller = (1175/200)    = 5.8    =6nos

. Spring constant = (E X A / L) 

where, E = 25000N/sq.mm

Area (A) = ( ∏/4 ) X ( 500)²  = 196349 sq.mm

Pile length = (L) = 16000mm

Spring constant =  E X A  =  26000 X 196349    = 306795 N/sq.mm

L 16000 Edge spacing is taken as 200 or 300mm.

Step 1 :- . Open SAFE application

. Slect new model

. Followed by input settings

. Select units as metric and code as IS456-2000

. 50mm top and bottom cover is provided.

Step 2 :- Cordinate wad define . Grid spacing in X and Y direction was taken as 2.9m and 1.65m . Shown below

Step 3 :- Define material property

Material property data : Click on define material properties M25 grade of concrete Modulus of elasticilty (E) = 25000N/sq.mm 

. Fe500 rebar are added as shwn below

Step 4 :- Define slab properties Define pile cap

. Define column

. Define pile details

. Step 5 :- Draw slab by using quick draw tool

Draw points

Step 6 :- Add piles at point Modify edge distance 0.3m

Step 7 :- Create column of 600X600m Draw column in center using quick draw tool

Step 8 :- Spring were added Select pile ----> assign ----> support data ----> sprong point Spring constaant is taken from above calculation

D.L and L.L are taken as 587.5KN

. Step 9 :- define load combination design

. Run analysis maximum displacement was found to be 0.84  Thus, safe

. All punching shear value are less than 1.....Thus, safe

. Joint reaction, rections are in limits.....Thus, safe

. Reinforcement detais in X and Y direction and run the analysis again

. Step 10 :- Reinforcement slab design

Pile cap foundation design

Result :-