prestressed concrete wing-shaped members are frequently used in the construction of long-span roofs in precast concrete buildings. Roofs spanning over
30 m (100 ft) are built by assembling a number of these thin-walled members, which may be placed side by side or with a certain transverse spacing, often rather wide, covered by ribbed slabs with curved shape. Figure 1 shows
an example of a roof comprising curved ribbed slabs supported by adjacent wing-shaped members resting on a main I-girder. The ease of fabrication of the wing-shaped members is comparable to that of a double tee but more difficult than an I-girder. Nevertheless, the use of wing- shaped members allows for better aesthetic results and for roofs having smaller mass with the consequent benefits in relation to seismic risk. To optimize the design of these thin-walled members and take advantage of their load- carrying capacity, prestressing is extensively used.
The exploitation of the mechanical properties of the mate- rials, the prestress force necessary to ensure an appropriate load-carrying capacity, and the requirement for in-service camber for aesthetic and functional reasons necessitate monitoring of prestress and camber. Inaccurate prediction of the camber can lead to unsatisfactory service conditions. Checking and monitoring of prestress loss and camber growth and investigations of the parameters that could affect them have primarily focused on bridge girders.