Concrete @ your Fingertips

Basis of design

The basic principle of prestressed concrete design is that some or all of the concrete cross-section is put into compression during the construction process. The arrangement of pre-compression is such that those areas of the structure that would be expected to go into tension under the loads applied in service (such as the sagging regions of beams) still remain in compression (or in very limited tension).

In contrast to conventional reinforced concrete design, that is based on ultimate strength with a check for serviceability performance, design of prestressed members is controlled by limits on the tensile and compressive stresses in service rather than at the ultimate limit state.

Appropriate guidance is given in the design Eurocodes. Eurocode 2; Part 1-1 covers buildings, Part 2 covers bridges and Part 3 covers Liquid retaining and containing structures. These parts of Eurocode 2 have replaced BS 8110, BS 5400 Part 4 and BS 8007.

Acknowledgement: The Concrete Society