The Design of Spread Footings Structural （立足点传播结构的设计）.pdf

Lecture #07 The Design of Spread Footings - Design Criteria - Design Procedure - Example Problem for a Square Footing - Example Problem for a Rectangular Footing -Example Problem for a Continuous Footing - Complex Cases The Design Procedure. 1. Determine the structural loads and member sizes at the foundation level; 2. Collect all the geotechnical data; set the proposed footings on the geotechnical profile; 3. Determine the depth and location of all foundation elements, 4. Determine the bearing capacity, 5. Determine possible total and differential settlements; check effects at 2B depths; 6. Select the concrete strength (and possibly the mix), 7. Select the steel grade, 8. Determine the required footing dimensions, 9. Determine the footing thickness, T (or D in some textbooks), 10. Determine the size, number and spacing of the reinforcing bars, 11. Design the connection between the superstructure and the foundation, and 12. Check uplift and stability against sliding and overturning of the structure-soil system. The first studies performed on foundation structural failures were done by Professor Talbot at the University of Illinois in 1913. Advances in the next 50 years include Prof. F.E. Richart’s tests at the University of Michigan. His results were synthesized into the methodology used today by a committee sponsored by the ACI and ASCE and published in 1962. Spread footings is still the most popular foundation around the world because they are more economical than piles, adding weight to them does not affect any other member, and their performance has been excellent. Selection of materials. Spread footings are usually designed to use 3 ksi f c 4 ksi, whereas modern structural members frequently use concrete between the range of 4 ksi f c 8 ksi. A higher concrete strength helps reduction the