Design of Reinforced Concrete Foundations Lecture (7) Design of Reinforced Concrete Foundations DR: Ahmed Afifi Ass. Teacher: Ahmed Said

INTRODUCTION TO FOUNDATIONS Function of a foundation is to transfer the structural loads from a building safely into the ground. Purpose of foundation:- To distribute the weight of the structural over large area so as to bring down the intensity of load at its base below the safe bearing capacity of sub-soil. To support the structures. To distribute the non-uniform load of the superstructure, uniform to the sub-soil.

The foundation can be broadly classified into: Shallow foundations Deep foundations

Types of Shallow Foundations: Placed immediately below the lowest part of the superstructure. Its purpose is to distribute the load over a wide area. Shallow foundations are usually embedded about a meter or so into soil Types of Shallow Foundations: Spread footing ( Rectangular, Square and Circular footing ) Combined footing Strap or Cantilever footing Strip footing Mat or Raft footing

1-Spread footings 2-Combined footings Such as rectangular and square footings are economical for support Column under normal condition 2-Combined footings Is a system of foundation that support more than one columns (usually 2 columns)

3-Strap footings 4-Strip footings When two columns are far apart, a strap is designed to transfer eccentric moment between two columns 4-Strip footings Strip foundations consist of a continuous strip, usually of concrete, formed centrally under load bearing. walls

5-Raft footings Raft foundation is a thick concrete slab reinforced with steel which covers the entire contact area of the structure like a thick floor. Sometimes area covered by raft may be greater than the contact area depending on the bearing capacity of the soil underneath. The reinforcing bars runs normal to each other in both top and bottom layers of steel reinforcement.