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footing for construction technology.pptx
- 1. SKY STAR EngineeringTraining Centre 6165-20-023- Construction Techniques 2 Principles Daw Saw Sandar Oo ME ( Civil )
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- 3. Building Foundation Foundation is partof a building, usually below the ground, that transfers and distributes the weight of the building onto the ground such that the compressive stresses do not exceed the bearing capacity of the soil.
- 4. The function ofany foundation is to safely sustain and transmit to the ground on which it rests the combined dead, imposed and wind loads in such a manner as not to cause any settlement or other movement which would impair the stability or cause damage to any part of the building. Foundation
- 5. Foundation Design Principles Themain objectives of foundation design are to:-ensure that the structural loads are transmitted to the subsoil safely, economically and without any unacceptable movement during the construction period and throughout the anticipated life of the building or structure.
- 6. Basic Design Procedure Assessmentof site conditions in the context of the site & soil investigation report Calculation of anticipated structural loading Choosing the foundation type, should consider: •Soil condition •Type of structure •Structural loading •Economic factors •Time factors relative to the proposed contract period •Construction problem Sizing the chosen foundation in the context of loading, ground bearing capacity & any likely future movement of the building / structure
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- 8. Classification of Foundation 8 Foundation Shallow Spreador Isolated Footing Strip or wall Footing Combined Footing Strap Footing Mat foundation Deep
- 9. The foundation runsunder all the loadbearing walls. A typical modern detached house will, where possible, sit on strip foundations. Providing the ground is suitable, this is the simplest and cheapest form of foundation. In this example this includes the external walls…… and the internal walls Strip Footing
- 10. Once the thetopsoil has been removed (and levels reduced if necessary), the foundation can be set-out by surveyors or engineers. The graphic on the left shows the foundation plan superimposed over the site. The line of the foundations can be highlighted using hydrated lime - here the trench centre line is being marked. On some sites you will find both sides of the trench marked. Digger buckets are available in various widths to suit specific trenches.
- 11. A continuous stripof concrete under a continuous wall carrying a uniformly distributed load.
- 12. Wide Strip Footing Usein a situation where the load bearing capacity of the soil is low (e.g. soft clay silt, made ground) Site which may be subjected to “unequal settlement” (mining areas), or where the subsoil is “not uniform” in character.
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- 14. A deep stripfooting is a narrow footing which is used for normal soil and normal loads and is made 0.9m deep. Excavation by hand is not possible. Brickwork cannot be built up from the bottom. Excavation by mechanical means is possible. Deep Strip Footing
- 17. Boning rod Site rail Siterail Correct depth can be checked with a Level and staff.
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- 19. A stepped stripfoundation is often used on a sloping site where the steps allow the foundation to follow the slope without too much excavation, when compared with excavations and retaining walls. Stepped Strip Footing
- 20. • Pad footingis the support used at a point load such as columns or framed structures. • They may be circular, square or rectangular and consist of a block or slab of the thickness. Isolated/ Pad Footing
- 21. • The padfooting may be stepped if they are required to spread the load from a heavy column. The pads are usually shallow but deep ones can be found depending on the structure. • Isolated or independent slab of concrete foundation to support concrete columns or steel pillars, detached brick or masonry piers • The pier or column bearing on the centre point of the slab
- 22. • Combined Footings– used where the bearing areas of closely spaced columns overlapped. Combined footings usually support two columns, or three columns not in a row. Combined footings are used when tow columns are so close that single footings can not be used or when one column is located at or near a property line. • Cantilever Footings – designed to accommodate eccentric loads
- 23. Stepped Footing Stepped Foundations~ these are usually considered in the context of strip foundations and are used mainly on sloping sites to reduce the amount of excavation and materials required to produce an adequate foundation.
- 25. Raft footing isa continuous footing that supports an entire structure, such as a floor also known as foundation mat. Best suited in the following conditions: Column loads are extremely heavy, thus requiring large bases Ground bearing capacity is low, such as in compressible soft natural Raft/Mat Footing
- 28. Pile foundation Pilefoundation is a special kind of deep foundation, where the depth of the foundation is much greater than the width of the foundation Today, pile foundation is much more common than any other type of deep foundation USES It is used where the soil is compressible, It is used where the soil is water logged It is used when stratum of required bearing capacity is at greater depth
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- 30. Major uses ofpiles : To carry vertical compression loads, To resist uplift loads To resist horizontal or inclined loads Classification of piles 1. Based on the function end bearing pile Friction pile Compaction pile Sheet pile Batter pile Tension pile Fender pile and dolphins
- 31. 2. Based onthe material& composition Concrete pile Timber pile Steel pile Composite pile: concrete& timber concrete& steel 3. Based on the method of installation; Driven pile cast-in situ pile Driven and cast-in-situ pile
- 33. Timber Piles ~these are usually square sawn and can be used for small contracts on sites with shallow alluvial deposits overlying a suitable bearing strata (e.g. river banks and estuaries.) Timber piles are percussion driven.
- 34. Preformed Concrete Piles~ variety of types available which are generally used on medium to large contracts of not less than one hundred piles where soft soil deposits overlie a firmer strata. These piles are percussion driven using a drop or single acting hammer.
- 35. Preformed Concrete Piles† jointing with a peripheral steel splicing collar as shown on the preceding page is adequate for most concentrically or directly loaded situations. Where very long piles are to be used and/or high stresses due to compression, tension and bending from the superstructure or the ground conditions are anticipated, the 4 or 8 lock pile joint may be considered.
- 37. Steel Box and`H' Sections ~ standard steel sheet pile sections can be used to form box section piles whereas the `H' section piles are cut from standard rolled sections. These piles are percussion driven and are used mainly in connection with marine structures.
- 38. Why Foundation isimportant? 38
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