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EGB273 (completed)
Foundations
| Question | Answer |
|---|---|
| Foundation Functions 1 | • Support imposed loads • Prevent settlement (including differential settlement) • Prevent possible movement of structure due to periodic shrinkage and swelling of subsoil |
| Foundation Functions 2 | • Allow building over water or water-logged ground • Resist uplift or overturning forces due to wind • Resist lateral forces due to soil movement • Underpin (support) existing or unstable structures |
| Foundation Functions 3 | • TO DISTRIBUTE THE LOAD OF STRUCURE ON LARGE AREA. • TO DISTRIBUTE THE LOAD ON UNDERLYING SOIL EVENLY . • IT PROVIDES A HARD AND LEVELED SURFACE FOR THE SUPER STRUCTURE. |
| Foundation Functions 4 | • IT RESISTS OTHER DISTURBING FORCES LIKE WIND, RAIN, ETC. • IT PREVENTS LATERAL MOVEMENT OF THE SPPORTING MATERIAL AND THEREBY ENSURY THE SAFETY OF STRUCTURE |
| LOADS ON FOUNDATION: | • 1. DEAD LOAD OF SUPERSTRUCTURE AND FOUNDATION • 2. LIVE LOADS • 3. WIND LOAD • 4. WATER PRESSURE • 5. LONGITUDINAL FORCES • 6. IMPACT LOADS • 7. TEMPERATURE STRESSES • 8. EARTH PRESSURE • 9. BOUNCY FORCES • 10. SEISMIC LOAD |
| Foundation Requirements - LOCATION: | THE FOUNDATION OF THE STRUCTURE SHOULD BE LOCATED IN SUCH AWAY THAT IT IS CAPABLE TO RESIST ANY UNEXPECTED EFFECT WHICH MAY ADVERSELY AFFECT THE PERFORMENCE OF THE STRUCTURE |
| Foundation Requirements - FOUNDATION SHOULD BE SAFE AND STABLE AGAINST ALL POSSIBLE... | FORCES TO WHICH A STRUCTURE LIKELY TO BE SUBJECTED TO |
| Foundation Requirements - SETTLEMENT: | STETTLEMENT OF THE STRUCTURE SHOULD BE WITHIN PEMISIBLE LIMIT |
| Performance or Choices 1 | • Nature of sub-soil (ground conditions) • Materials used for the foundation • Economical consideration • Construction program |
| Performance or Choices 2 | • Layout of structure (building/floor plan, positioning loads etc) • Site constraints (location and sufficient work space) • Local availability of plant and equipment • Acceptable settlement |
| Types of Foundation | Shallow - Pad Deep - Piled |
| Shallow - Pad | Strip footing, Pad (or Spread) footing, Raft (or Mat) footing, Strapped (or Combined) footing |
| Deep - Piled | Bored cast in-situ, Driven cast-insitu, Driven precast concrete/steel/timber |
| Shallow Foundations | • Shallow foundations take their name from the level they are founded • Typically lighter load than deep (piled) foundation • Much cheaper to construct • No specialist equipment needed |
| Deep - Piled Foundations | TRANSFERING FOUNDATIONS TO A CONVENIENT LEVEL, A FIRM SOIL STRATUM WITH SUFFICIENT LOAD CARRYING CAPACITY |
| Piling Types 1 | • DISPLACEMENT (DRIVEN PILES ) – Timber – Precast concrete (sometimes prestressed) – Closed ended steel tube – Steel “H” sections |
| Piling Types 2 | • CAST IN PLACE – Bulb piles – Bored piers – Grouted piles |
| Piling Types 3 | • FURTHER SUBDIVIDED INTO: – End bearing piles – Friction piles – Combination of both |
| Types of materials used for deep foundations: | Timber Steel tube Steel H section Concrete (reinforced) Concrete (prestressed) Steel tube (concrete filled) Composite (steel/concrete) |
| DRIVEN PILES | • FORCE APPLIED TO TOP, USUALLY THROUGH IMPACT (SOME BOTTOM DRIVEN) • BLOW CUSHIONED FOR CONCRETE PILES • INITIALLY GUIDED BY FRAME • CAPACITY DETERMINED BY RESISTANCE TO DRIVING • PROBLEM OF PREDICTING LENGTH |
| When piles are being hammered into the ground, Induced waves can cause danger when a soft patch is encountered and the pile goes into tension... | leading to a crack developing and spalling occurring at a new interface |
| CAST IN PLACE PILING | EARTH DISPLACED AND REPLACED BY CONCRETE - Materials transported in most convenient form - Readily adjusted to actual conditions - Most suited to light construction (BUILDING) - “Not able to be inspected” - Backed by insurance guarantee |
| Bored Piers | Used when: - Load is relative large - The depth is too shallow for driven piles - Vibration or noise must be avoided |
| Bored Piers may be... | socketed or end-bearing (bell-out) |
| Bulb Piles | Used when: - There might be upper loads |
| Bulb Piles may be... | socketed or end-bearing (bell-out) |
| Structural Considerations for Cast in Place Piling | Designed shape sensibly within the actual shape Possible intrusion of soil into reinforcing Soft layers compacted by concrete |
| Other uses of piles include Bored piles used as... | excavation support |
Created by:
Asher - S
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