oa Civil Engineer in South Africa - Towards direct design of shallow beams and slabs in accordance with CP110

Volume 21, Issue 12
  • ISSN : 0009-7845



Design of slabs and shallow beams frequently reduces to ensuring simultaneous compliance with the strength and deflection limit states or, in effect, assessing correctly the modification factor that will emerge from Table 10 of CP110 after determination of the proportion of reinforcement. This Table is awkward to use, particularly if the service stress differs from the tabulated values, since it involves non-linear interpolation between values of two variables which are mutually dependent. The result of an incorrect first assumption gives insufficient guidance for the next approximation, which can result in an unstable convergence to the limiting design. The equations involved are transcendental, preventing the use of direct solutions.

Five charts are presented which simplify the use of Table 10, permit an accurate prediction of the limiting factor from this Table for any given loading and enable accurate prediction of any subsequent modification of effective depth or service stress that may be necessary. The use of charts is illustrated by examples which include cases not explicitly covered by the Code.

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