ABSTRACT
Step 5 Since the tendon profile in Step 4 is concordant (Rule 4) and since it lies within the permissible zone, it is acceptable.
Step 6 From eqn (9 .3 -7 ), the prestressing force at transfer is
P = p j a = 1000/0.85 = 1175kN
Consider Section B (Fig. 10.5-1) From eqn (10.4-1), bottom fibre stress is
P , _ M imax + Mq A Z, Z, = 1175 x 103 1175 x 103(-1 6 7 ) _ Q - 36.8 x 106
160 x 103 22 x 106 22 x 106 = 0.097 N/mm2 > / amjnt of - 1 N /m m 2
Therefore this is acceptable. From eqn (10.4-3), top fibre stress is
= 1175 x 103 _ 1175 X 103 x (-1 6 7 ) 0 - 36.8 X 106 160 x 103 23 x 106 23 x 106
= 14.3 N/mm2 < / amaxt of 16 N/m m 2
Therefore this is acceptable. Equations (10.4-2) and (10.4-4) are not critical. Similarly, it can be
shown that stresses are everywhere within the allowable values at transfer. (Note: If the ‘kink’ of the tendon at B is considered too sharp, this can be reduced by linear transformation. After such linear transformation, the tendon may be outside the shaded zone in Fig. 10.5-1, but this does not matter, because (Rule 2) the line of pressure remains within the zone.)
Example 10.5-2 Explain whether the following statements are true or false:
(a) The line of pressure (line of thrust) in a prestressed concrete con tinuous beam is a linear transformation of the tendon profile.
