9.2 parameters affecting the value of the modular ratio

Significant research has been carried out on creep and shrinkage for reinforced concrete members, within Australia  which has been incorporated successfully within  Australian  Concrete Standards since 1978 to the present. The principles used in these standards have been  employed  in the formulation of these span tables with the following consequences:

(a) A greater variance occurs for values of modular ratio ranging from a short term load value of approximately 12, but approaches a limiting value of 26  for dead load.

(b) Values of creep and shrinkage are not only governed by the duration of loading, but also the age of the concrete  at first load and the  air environment around the slab.

(c) The theoretical thickness has a direct bearing on the value of creep occurring. Increasing the depth of a member will cause a relative decrease in the value of creep.

(d) An ultimate value of 2.35 has been used for the creep  coefficient (ultimate value of the creep strain to the instantaneous or ‘elastic’ strain)