Chapter 3 building foundation
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This document discusses foundations for buildings. Foundations spread the load of the building to the ground to limit soil settlement. Foundations must be located safely and distribute dead, live, and wind loads appropriately. There are shallow and deep foundations. Good foundation design ensures loads are distributed economically, safely, and without movement during/after construction. Methods for foundation design include site investigation, load analysis, foundation material selection, and working drawings. Load bearing capacity depends on soil analysis and testing. Techniques to increase capacity include deeper foundations and soil compaction. Settlement and differential settlement can occur and techniques aim to reduce them, like raft foundations. Foundation type selection considers soil conditions, building type/loads, costs, and surroundings.
Chapter 3 building foundation
- 1. FOUNDATION
- 2. INTRODUCTION Building Foundation is an underground structure that directly in contact with the soil and spread the load of building to the ground so as to limit the soil settlement of the building. In certain circumstances, it is also to withstand the wind pressure.
- 3. FUNCTION Spread the load of building structures to the broader and stronger area. Spreading the load with uniform and constantly (avoid differential settlement) To strongly hold the frame of building, especially in high-rise buildings Prepare a hard and flat surface
- 4. REQUIREMENTS Located in a safe place and to distribute all loads such as dead load, live load and wind load in an appropriate manner. Sufficient in depth Resistant to sulfate attack
- 5. TYPE OF FOUNDATIONS Shallow foundation Strip Pad Raft Deep Foundation Piling Hollow basement, caisson
- 6. DESIGN CRITERIA FOR FOUNDATION Good foundation design is to ensure that the structure load including the mass of foundation distributed by: Economical Safe No movement during or after construction
- 7. METHODS IN FOUNDATION DESIGN Site Investigation Magnitude and distribution of loads from the structure is divided by dead load, life load and vibration (dynamic loading) and also wind pressure. Overall total of settlement and the differential settlement Foundation Types Allowable bearing pressure value of load
- 8. CONT… Pressure distribution under foundation calculation Analysis of settlement Foundation material Structure design working drawing
- 9. LOAD BEARING CAPACITY Ultimate bearing capacity Safe bearing capacity Load bearing strength is determined by the following : a) Ranking Analysis b) Penetration Test c) Persumptive value
- 10. METHODS TO INCREASE LOAD BEARING CAPACITY Increase the depth of foundation soil compaction: a. Vibration b. Preloading c. Water flowing d. Grouting
- 11. SETTLEMENT Definition: Downward vertical movement due to the load pressure on them. Divided into two a) Immediate settlement-occur when the soil is imposed by the load from soil elastic deformation where it does not change the water content b) Consolidation Settlement-reduction in the volume of soil due to water flowing out from the grain cavities.
- 12. CAUSES OF SETTLEMENT Structure pressure to the ground Changes in soil water content The vibration caused by impact piling, blasting and heavy machinery. Expansion and contraction of soil Movement / soil erosion Other causes, such as soil digging in the nearby area
- 13. DIFFERENTIAL SETTLEMENT Definition: the relative settlement between one part of the building to the other part of building and cause the stress that can result building to crack or collapse
- 14. SOURCES OF DIFFERENTIAL SETTLEMENT Differences in soil layers in a single site The difference in the load structure Large load area The time difference between the construction of other parts of the building Differences in site conditions.
- 15. METHODS TO REDUCE DIFFERENTIAL SETTLEMENT Use raft foundation with a thick slab Use deeper underground space to reduce pressure on soil. Transfer load to the stronger and not easily compressible soil with the foundation applied such as piles, caisson, etc. Method of repair of soil - increase in soil strength
- 16. SELECTION OF FOUNDATION’S TYPE Condition and soil strength The nature and type of building The total loads of building Surrounding area Cost