Foundation & Footings

A foundation is the lowest part of the building structure. It is the engineering field of study devoted to the design of those structures which support other structures, most typically buildings, bridges or transportation infrastructure. It is at the periphery of Civil, Structural and Geo-technical Engineering disciplines and has distinct focus on soil-structure interaction.

1. Foundation & footing COURSE CODE : CE – 200 COURSE TITLE : DETAILS IN CONSTRUCTION & ESTIMATING Dept . Of civil engineering, cuet

2. What is Foundation ? According to Wikipedia, A foundation is the element of an architectural structure which connects it to the ground, and transfers loads from the structure to the ground. It is a complex term used in geotechnical engineering to denote the soil and footing and their interaction that provides bearing capacity as well as settlement resistance to the super structure. Specially designed foundation helps in avoiding the lateral movements of the supporting material. Fig. 1- Concrete frame structures with foundation.

3. What is footing ? " Footing " is  defined  as a structure constructed in brickwork, masonry or concrete under the base of a wall or column for the purpose of distributing the load over a larger area. It is more from a structural aspect that would transfer the axial load from the column to the soil. Footing can be idealized during analysis as supports. The  purpose of footings  is to support the  foundation  and prevent settling. Fig. 2- Footings supporting the foundation.

4. Why foundation & footings ? Fig. 3- Consecutive process of building a house.

5. Types of footings Isolated footing Combined footing MAT or raft footing Pile foundation Pile raft foundation SHORE pile or sheet pile protection system

6. Isolated footing

7. ISOLATED FOOTING Fig. 4 – Isolated Footing. Captured from the Water Tank area of CUET where Engineering Office cum Central Parking is going to be built. This picture was captured on October 4, at 6 : 30 am

8. Isolated footing DEFINITION : Isolated footing  is defined as the  footing , which is provided beneath the column to distribute the loads safely to the bed soil. This kind of  footing  is used to support single-columns and when the columns are arranged relatively at long distance. Fig. 5- Detailed Layout

9. Area of application Commonly used for shallow foundations in order to carry and spread concentrated loads, caused for example by columns or pillars. Isolated footings can consist either of reinforced or non-reinforced material. For the non-reinforced footing however, the height of the footing has to be bigger in order to provide the necessary spreading of load. Should only be used when it is absolutely certain, that no varying settlements will occur under the entire building. Spread footings are unsuitable for the bearing of widespread loads. In this case, either strip (continuous) footings or mat footings are used. Fig. 6- Steel framework for isolated footing.

10. COMBINED FOOTING

11. cOmbined footing Definition : A strap  footing  is a component of a building's foundation. It is a type of  combined footing , consisting of two or more column  footings  connected by a concrete beam. Fig. 7- Combined footing.

12. Area of application   The distance between two columns is small and when soil bearing capacity of soil is lower and their footings overlap with each other. When one column is close to a property line or sewer pipe, the centre of gravity of column will not coincide with footing. In such cases, it is necessary to provide combined this footing with that of the adjacent internal column.   Dimensions of one side of footing are restricted to some lower value so that column footings may be combined Fig. 8 - Steel framework for combined footing using AutoCAD.

13. MAT OR RAFT FOUNDATION

14. MAT OR RAFT FOUNDATION Fig. 9- Mat Foundation of a site. Fig. 10- Layout of Raft Foundation using AutoCAD.

15. Mat or raft foundation Definition : According to the Dictionary of Earth Sciences, Raft foundation, a type of foundation, used for heavy loading, or construction on soft ground, composed of a continuous slab of reinforced concrete below the entire surface. In  V enice, many of the mediaeval raft foundations underneath the large churches are made of wood. Fig. 11- Raft Foundation of a site.

16. Area of application Raft foundations  may be used for buildings on compressible ground such as very soft clay, alluvial deposits and compressible fill material where strip, pad or pile foundations would not provide a stable foundation without excessive excavation. The reinforced concrete raft is designed to transmit the whole load of the building from the raft to the ground where the small spread loads will cause little if any appreciable settlement.

17. Pile foundation

18. Pile foundation Fig. 12- Pile Foundation of a site. Fig. 13- Pile Heads found at a site.

19. Pile foundation Definition : Pile foundation , a substructure in which  piles  are used to transfer a load from a structure to the soil.  Pile foundations  are particularly appropriate when the building or structure is to be erected on soil that is not stable or is saturated with water. Fig. 14- Simple sketch of pile foundation

20. Area of application It is used When stratum of required bearing capacity is at greater depth. Where the soil is compressible. Where the soil is water-logged. Where the soil is of made-up type. Examples : Foundation of heavy bridges, high-rise buildings Water front installations (pier, wharf, docks etc.)

21. Piled raft foundation

22. Piled raft foundation Fig. 15- Piled Raft Foundation on AutoCAD. Fig. 16- A part of Piled Raft Foundation.

23. Piled raft foundation Definition : The combined  pile raft foundation  (CPRF) is a geotechnical composite construction that combines the bearing effect of both foundation  elements  raft  and  piles  by taking into account interactions between the  foundation  elements and the subsoil.

24. Area of application The addition of piles to a raft increases the effective size of a foundation and can help resist horizontal loads. This can improve the performance of the foundation in reducing the amount of settlement and differential settlement, as well as improving the ultimate load capacity. Piled raft foundations are typically used for large structures, and in situations where soil is not suitable to prevent excessive settlement. They are an increasingly popular choice for high-rise buildings. During the design process, the optimum number and position of piles, as well as their diameter, reinforcement and length, is determined to ensure the stability of the structure while providing an economical solution, with the raft and piles acting together to ensure the required settlement is not exceeded.

25. Shore pile or sheet pile protection system

26. Shore pile or sheet pile protection system Fig. 18- Shore P ile P rotection S ystem. Location : M adunaghat Water Treatment P lant, M adunaghat, H athajari, C hittagong. This photo was captured on March 2018.

27. Shore pile or sheet pile protection system Fig. 19 & 20- From these two images we see that the site areas are surrounded by sheet pile protection system.

28. Shore pile or sheet pile protection system DEFINITION : SHORE PILES are  generally  piles sunken support for building: A vertical wood, metal, or concrete support for a building or other structure that is driven into the ground  shore piling  is a commonly used term before installation of the mat foundation of the building needs to be done. Fig. 21- This type of shore piles were made for making piers during the construction of Bohoddarhat Flyover at Chittagong.

29. Area of application When construction is taking place in a confined space, then temporary walls are used to prevent cave-ins; offering protection to the workers working in the vicinity of the area. In a home environment, sheet piling is used as permanent walls as they provide stability and durability to the interior walls (especially basement walls). Pilling is also used to prevent floods to structures close to shorelines. To protect foundations from water damage. To support excavations for parking structures, basements, foundations, pump houses, and to construct cofferdams, seawalls and bulkheads

30. Thanks for your patience !