building construction lecture 3

design & construction of reinforcement concrete foundations

1. Foundations are usually made of either mass or reinforced concrete.
2. Where a structure has olny light loadings , such as a domestic building , it is sufficient to use a mass concrete foundations .
3. Where buildings are either heavy , or transmit the loadings at a series of points , such as in a framed buildings , it is uneconomic to use mass concrete foundation.
4. Where byulding either heavy or transmit the loadings at a series of points , such as in a framed building , it is uneconomic to use mass concrete foundation.
5. The thickness of a mass concrete foundations for a heavy point load would result in a foundation that is costly and adds unnecessary load to the subsoil.
6. Reinforced concrete foundations are generally cheaper and easier to construct than mass concrete foundations but will require a structural engineer to formulate an economic design .
7. The engineer must define the areas in which tension occurs and specify the reinforcement require , as concrete is material which is weak in tension
8. Concrete is a mixture of cement , sand , aggregates and water in controlled proportions .
9. It is the most suitable material to construct foundation as it is a durable material of adequate strength
10. But concrete is a material which is strong in compression but weak in tension .
11. If its tensile strength is exceeded , cracks will occur and resulting in a weak and unsuitable foundation.
12. One method of providing tensile resistance is to include steel bar as a form of teinforcement in the concrete foundation to resist all the tensile forces induced into the foundations .
13. Steel is material which is readily available and has high tensile strength.