Building construction redo
- 3. Purpose • Distribute the load • Make the bearing surface uniform • Prevent movement • Increase stability Ground Level Super-structure foundation Distribute building load to the ground
- 4. Size and depth of a foundation is determined by: Structure and size of building it supports Nature and bearing capacity of the ground supporting it
- 5. The two basic types of foundations: Shallow Deep
- 8. Definition It extends down through unsuitable or unstable soil to transfer building loads to a more appropriate bearing stratum of rock or dense sands and gravels. Unlike shallow foundations, deep foundations distribute the load of into the ground vertically rather than laterally.
- 9. Cases • Weak soils near the surface • Loads very high • Soil stratum is not strong or stable Example: Petronas Twin Towers in Malaysia
- 10. The Two Principal Types of Deep Foundations: Pile Caisson Pile
- 11. Pile Foundation
- 12. Definition A system of end bearing or friction piles, pile caps and tie beams for transferring building loads down to a suitable bearing
- 13. Types Piles may be of treated timber poles but for large buildings, steel H sections, concrete filled pipes, or precast reinforced or prestressed concrete are more common. Timber H-Sections Pipe Piles Precast Concrete
- 14. Cases • Stratum of required bearing capacity is at greater depth • Steep slopes • Compressible soil • Water-logged soil • Soil of made-up type Slope
- 15. Advantages • Can be used for any type of structure and in any type of soil. • Can be precast • Can be used in places where it is advisable not to drill holes Disadvantages • Must be reinforced to withstand stresses • Requires heavy equipment for handling and driving. • Foundations of adjacent structures are likely to be affected due to the vibrations
- 16. Process and Machinery Piles are driven into the earth by a pile driver, composed of a tall framework supporting machinery for lifting the pile in position before driving, a driving hammer, and vertical rails or leads for guiding the hammer
- 17. Pile driver For driving piles into the ground
- 18. Driving Hammer
- 19. Drilling rig Creates holes in the earth sub-surface
- 20. Classification of Pile Foundation Based on Function End-Bearing Piles Friction Piles
- 21. End-Bearing Pile Depends principally on the bearing resistance of soil or rock beneath their feet for support.
- 22. Friction Bearing Pile Depend principally on the frictional resistance of a surrounding earth mass for support.
- 24. Definition Formed by boring with a large auger or excavating by hand a shaft in the earth to a suitable bearing stratum and filling the shaft with concrete Auger
- 25. Crane Crane for filling caisson
- 26. Cases • Suitable for underwater foundation where the foundation should be extended up to or below the river bed to obtain stability • Often used when constructing bridge piers and other such foundations
- 27. Advantages • Extended to large depths • Cost is relatively less • There is direct and easy passage to reach the bottom of caisson so any obstruction can easily be removed. Disadvantages • Precautions should be taken, otherwise it may lead to fatal accidents. • Labor cost is high. • If obstacles like boulders or logs are encountered, then progress becomes slow.
- 28. A temporary casing may be required to seal out water, sand or loose fill from the shaft during excavation
- 29. The base of a caisson may be enlarged into a bell shape to increase its bearing area and resist uplift from soil expansion. The bell may be excavated by hand or be formed by a bucket attachment to an earth auger that has a set of retractable blades Some caissons are drilled into a stratum of solid rock in order to gain additional frictional support
- 31. Definition • Does not use footings • Support on soft soil • Consists of a stiff reinforced concrete slab • Distributes the load by columns to the soil Why is it called “floating”? Because it "floats" on the soil.
- 32. Cases • Often seen in warmer climates Why? Ground freezing and thawing is less of a concern No need for heat ducting underneath the floor • Common in garage floors and mobile home slabs
- 33. Process Install reinforced steel rods or heavy wire mesh (to prevent floor from cracking and breaking) Pour concrete
- 34. Advantages • Termites are not a problem • Inexpensive • Moisture barrier • For areas with lower load bearing capacities Disadvantages • Expansion not possible • Lack of underground access • Exposes the building to flood damage in even moderate rains