It is a simple presentation on comparison between square and raft footing on basis of material used ,settlement and cost.

1. Structural Engineering
Civil Engineering Department
MNNIT ALLAHABAD
Supervisor(s) –
Dr. L.K. MISHRA
Dr. GOUTAM GHOSH
Presented By-
Lovneesh Modi
2016ST02
A SUMMER PROJECT PRESENTATION
On
Comparison Of Square And Raft Footing For A Multistory Building
Under Static And Dynamic Loads

2. List of Contents
1.Introduction
2.Objectives
3.Methodology
4.Problem Definition
5.Results
6.Conclusion
7.Reference

3. Introduction
Foundation is the structure element that transfers the load from column or load
bearing wall to ground.
It can be classified as :-
1. Shallow :-Depth upto 2 m
2. Deep :- Depth more than 2m
We are focusing on the each of the two types of shallow foundation:-
1. Isolated column footing
2. Mat/Raft foundation
Image source:- strucalc.com

4. Objectives
• To evaluate the Soil Bearing capacity according to IS 6403-1987 and
Settlement from the available Bore log data
• To identify the suitable type of foundation for given condition
• To design the foundations using Staad Foundation advanced

5. Methodology
• Application of problem formulated by analyzing it in Staad-Pro
• Export the reactions from Staad Pro to the Staad foundation
Advanced for modeling, analysis and design of the foundations
• Comparison of the Results in terms of SBC, Settlement and Quantity
of materials

6. Problem Definition
The dimensions taken are as follows:-
• Beams 300x450mm2 and Column 500x500mm2
• Dead load 3.75kN/m2 (assume 150mm slab)
• Floor to floor height is 3m and column to column distance is 10m
• Live load 2 kN/m2 (according to IS 875 Part2-1987)
• Wind load taken according to IS 875 Part3-2015
• Seismic Loads are taken according to IS 1893 Part1-1993

7. FOUNDATION DESIGN
DEFINE
ASSUMPTIONS
DESIGN CHECK AND
REINFORCEMENT
DESIGN
STRUCTURAL
ANALYSIS
PRELIMINARY
DESIGN BASED ON
SERVICE LOAD
Soil Bearing
Capacity
Depth of footing
Water Table
Concrete and
soil Unit Weight
Calculate required
foundation
dimension based
on required area
Required
foundation area
Calculate
factored footing
pressure
Calculate
maximum shear
Calculate
maximum
moment
Overturning
Sliding
One way shear
Punching shear
Choose governing area
of steel and determine
spacing required
CHECK
Calculate
maximum
moment

8. Advantages/Disadvantages
of the Staad Foundation
Advantages Disadvantages
Quick and easy assessment of stresses Settlement calculation is not possible
Effortless design of footing according to IS 456-2000 Calculation of SBC for isolated column footing is to be
manually provided
Quick extraction of detail drawing of the structural
component(only for isolated and combined footing)
Collaboration of model with BIM workflow is yet not
possible

9. Results
Isolated(square) Raft
Safe bearing capacity 235 kN/m2 least calculated 476 kN/m2
Settlement 144 mm(allowable 60 mm) 65mm(allowable 75 mm)
Maximum dimension 3.85x3.85 - 6.3x6.3 m2 35 x 45 m2
Thickness of footing 450 - 670 mm 600mm
Concrete 432m3 945 m3
Steel 33.868x 103 Tonnes 2.921x 103 Tonnes
Cost of concrete excluding
centering and shuttering(in Rs)
33,64,848(@7789 per m3) 73,60,605(@7789 per m3)
Cost of steel (in Rs) 2,16,75,52,000(@ 64 per kg) 18,69,44,000(@64 per kg)
Total Cost(in Rs) 2,17,09,16,848 19,43,04,605

10. Footing
Name
Settlement
(mm)
Square Size(m) X
(m)
Z
(m)
SBC(kN/m2) Base Pressure
(kN/m2)
footing 1 61 5.15 0 0 244 55
footing 2 78 6.15 10 0 252 78
footing 3 78 6.15 20 0 252 70
footing 4 61 5.15 30 0 244 55
footing 25 79 6.1 0 10 251 70
footing26 144 5.75 10 10 248 130
footing 27 144 5.75 20 10 248 131
footing 28 114 4.8 30 10 241 105
footing 49 75 6.3 0 20 253 66
footing 50 139 5.85 10 20 249 126
footing 51 137 5.95 20 20 250 123
footing 52 114 4.8 30 20 241 104
footing 73 79 6.1 0 30 251 70
footing 74 141 5.8 10 30 249 129
footing 75 142 5.8 20 30 249 129
footing 76 112 4.85 30 30 241 103
footing 97 62 5.1 0 40 243 55
footing 98 118 4.7 10 40 240 110
footing 99 116 4.75 20 40 240 108
footing 10097 3.85 30 40 235
94

11. The maximum Base pressures or reaction of the mat comes out to be 79 kN/m2and average reaction is 10 kN/m2.
The maximum bearing Stresses in mat is 29.5 N/mm2 and average is 3.76 N/mm2

12. Conclusion
• For the frame structure and given soil type Raft foundation comes out
to be most efficient in terms of settlement , strength and economy
• Design of bearing stresses being important in Raft for which
additional reinforcement in the form of dowel bars should be
provided.

13. References
1. IS 1893 – 1993Part 1 “Criteria for Earthquake Resistant Design of Structure”
2. IS 1904 – 1986 ”Design and Construction of Foundation in Soils”
3. IS 6403 – 1981 ”Determination of Breaking Capacity of Shallow Foundation”
4. IS 456 -2000 ”Plain and Reinforced Concrete”
5. CPWD Detail Schedule of Rates (2014)