Civil Engineering Reference
In-Depth Information
Figure 6.25
Free cantilever construction: self-weight effects
structure, the
Pe
would of course have been the same, but in addition there would have
been a hogging (negative) parasitic moment (as all the cables are above the neutral
axis). The monolithic prestress moments are shown in Figure 6.26 (d).
The structure is now made continuous by the mid-span stitch, and the prestress
defl ections increase due to creep. As the structure creeps, a parasitic moment will be
created that reduces the effectiveness of the prestress at the supports. This parasitic
moment gradually tends towards the monolithic value. The design prestress parasitic
moment lies between the as-built and monolithic extremes, and is obtained using the
equation shown in
16.21.1
above.
