Equivalent area of voided slabs

In order to calculate prestress losses in the transverse prestressing of vo ided concrete slabs, it is sometimes convenient to estimate the thickness o f an equivalent solid slab. The Ontario Highway Bridge Design Code, as well as the forthcoming Canadian Highway Bridge Design Code, specifies a simple expression for calculating this equivalent thickness. This expression is r eviewed in this technical note, and a simple alternative expression, believ ed to be more accurate, is proposed, along with its derivation. It is shown that the equivalent solid slab thickness obtained from consideration of in -plane forces is also applicable to transverse shear deformations, provided that the usual approximations of elementary strength of materials are used in both cases.