Required final prestress

Final prestress and losses are interdependent therefore d value for final prestress will be estimated and losses will be calculated. Then the process will be repeated to see if changes are required for final prestress. 

From sheet 13 the required force is 530 k/ft however the prestress force may be reduced because of Tendon Elongation. Since tendon elongation depends of final stress in tendon, an estimate of this will be made and the reserved later time. 

Strengthening method is to use external posttensioning as shown in Fig. 13a. Steel jackets bonded to the sides of the joint and anchored to the bent cap are also effective (Thewalt and Stojadinovic 1995). Finally, FRP jackets in the form of an ankle wrap have been tested (Gergely et al. 2000) and used to strengthen column to cap beam-colunm joints as shown in Fig. 13b (Pantelides et al. 2004). The nominal principal tensile stress developed in the beam-column joint is used to design the carbon FRP composite layers. When strengthening of these joints is required to improve the longitudinal response, transversely prestressed bolsters may be used. 

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