10.0 design for concrete shrinkage

This manual places significant emphasis on the effects of creep and shrinkage in design. It must be stressed that these aspects of design are not a function of the tray-floor, but occur in all concrete structures. As such the performance of reinforced concrete, prestressed concrete, and composite concrete ( both prestressed and tray-floor) all rely on the designer taking proper account of creep and shrinkage. however, while most technical manuals have previously made some allowance for creep they have not generally included shrinkage effects.

Both creep and shrinkage contribute to the increase with time of deflection in flexural members. For commonly proportioned members the deflection contribution due to creep is less than that due shrinkage. Given that creep effects can lead to a final deflection three times that of initial elastic deformation, the inclusion of shrinkage is imperative to competent design.

Designers should be aware that proper allowance for shrinkage is mandatory and that it is imperative that  proper assessment is made with regard to building boundary restraint and connection interactions. Failure to do so could lead to excessive cracking and crack widths or magnified midspan deflection.