Building Construction II

Foundation has direct contact with, and transmits loads to, the ground.

Ground stability – immediate and consolidate settlement. Differential settlement occurs in building uneven load distribution.

• Rock – hard, rigid i.e. granite, sandstone and limestone
• Soils – soft, loose i.e. gravel, sand and clay.
• Ground stability – Landslip, flood, mining and landfill.

Functional requirements

The most important is strength and stability. Loading is concerned with the soil bearing strength in relation to loads applied.

1. Bearing capacity
Rock or soil should strong so that will not impair the structure.
Table shown is the bearing capacity for each rock/soil type. In some situation i.e. the soil need more Exploration.

2. Foundation design

Failure may be due to;
1 excessive settlement
2 collapse of subsoil
3 differential settlements

Designing foundation is:
1 site condition
2 characteristic of structure

3. Bearing pressures

The intensity of pressure on subsoil
is not uniform. Engineer is to find out pressure at various depths.
Low bearing pressure at lower stratum if found than the foundation has to be redesign.

4. Contact pressures

The contact pressure on cohesive soil (i.e. clay) is less at the edge of foundation when yielding of the clay. As more load toward center the yielding at clay increased.
Foundation on a cohesive soil would be arranged with major loads towards the center
of the foundation where the pressure intensity is less.

5. Differential settlement

D.S. occurs due to:
- Variation of loads and subsoil.
- Different rates of settlement.
Structural system chosen will determined the degree of affect of building due to D.S.

6. Shrinkable soils and vegetation

Type of soil and position of vegetation and
Trees will affect the depth of foundation.