Foundation Design using SAFE

CHALLENGE WEEK 12

ETABS

Question no.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.

Answer:

• AIM:

• To model isolated footing.
• To verify the design according to said specification

• Procedure:

• Data required for SAFE analysis & design

• Unfactored load = 2000/1.5 = 1333.3KN
• Dead load breakup = 1333.3/2 = 666.7KN
• Live load breakup = 1333.3/2 =666.7KN

Subgrade modulus for soil = Safe bearing capacity * factor to ultimate/max settlement

= 150* 3/0.05 = k= 9000KN/m³

Rebar yield strength (Fy) = 500N/mm²

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

Elastic modulus of M25 Concrete = 25000N/mm²

• Then we are going for the checks using the safe software

• Initially we are setting up the initial settings
• And choosing single column as designed in the week 11 challenge

• And then adding up M25 adn Fe 415 for concrete and steel properties respectively.

• Then we are setting up teh slab section

• And then the soil surcharge

• And then we are setting up or checking the load combinations

• After the model part is completed we are going for a analysis

• Then we do some checks like reactions

• Punching shear

• Strip forces

• And then we are going for a slab design check

• Result:

• Hence the model was calculated
• And the model was checked using SAFE Software.

Question no.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:

Answer:

• AIM:

• To design and analyse a the pile cap.
• To follow the said specifications.

• Procedure:

• Data required for SAFE analysis and design

• Unfactored load = 1175KN
• Dead load breakup = 1175/2 = 587.5KN
• Live Load breakup = 1175/2 = 587.5
• Point spring of pile = A*E/L

= 196349*25000/16000 = 306796 KN/m

k for SAFE analysis = 306.8KN/mm

Rebar yield strength (Fy) =500N/mm²

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

Elastic modulus of M25 Concrete =25000N/mm²

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

1175*1.1/200 = 6.5

Consider 8 piles for symmetric placement of piles under pile cap

Take center to center distance between piles = 3*pile diameter (1500mm)

Edge distance from pile center = 1*Pile diameter (500mm)

Assumed pile cap depth = 500mm