Foundations theory
Summary Thursday, April 19, 2012 9:08 AM
Foundation Design Loads are transmitted to the foundation Superstructure: above ground Substructure: below ground (foundation)
Important soil characteristics 1. 2. 3. 4. 5.
Soil type Bearing capacity Settlement at different pressures Location of water table Vibration characteristic if the structure is subjected to dynamic loads
Importance of foundations • Performance of structure is influenced by the performance of the foundation • Foundations transfer and spread the loads from columns, walls and piers into the ground at a level where safe bearing capacity is not exceeded
Types of foundations • Shallow ○ Sufficient bearing capacity can be achieved shallow into the ground ○ Spread foundations ○ Raft or Mat foundations When soil bearing capacity is low When column loads are so large that if spread footings were used, they would cover most of the area of the building Inverted solid two-way slabs Extremely stiff Able to reduce both "total" and "differential" settlements • Deep foundations ○ In case of very weak surface or near surface soils ○ Piles May be vertical or slanting (raking) Detailed soil survey End bearing or friction or combination of both In large group of piles of closely spaced friction piles: load bearing capacity
Foundation Design Loads are transmitted to the foundation Superstructure: above ground Substructure: below ground (foundation)
Important soil characteristics 1. 2. 3. 4. 5.
Soil type Bearing capacity Settlement at different pressures Location of water table Vibration characteristic if the structure is subjected to dynamic loads
Importance of foundations • Performance of structure is influenced by the performance of the foundation • Foundations transfer and spread the loads from columns, walls and piers into the ground at a level where safe bearing capacity is not exceeded
Types of foundations • Shallow ○ Sufficient bearing capacity can be achieved shallow into the ground ○ Spread foundations ○ Raft or Mat foundations When soil bearing capacity is low When column loads are so large that if spread footings were used, they would cover most of the area of the building Inverted solid two-way slabs Extremely stiff Able to reduce both "total" and "differential" settlements • Deep foundations ○ In case of very weak surface or near surface soils ○ Piles May be vertical or slanting (raking) Detailed soil survey End bearing or friction or combination of both In large group of piles of closely spaced friction piles: load bearing capacity
