Civil Engineering Reference
In-Depth Information
Figure 5.15
Loss of prestress due to friction and anchor set
where the beam is precast in short lengths will usually increase the wobble. The most
rational way to calculate the loss of force due to wobble is to add a notional angular
deviation to the intended angular deviation. The equation then becomes
P
x
=
P
0
e
-µ(Σα + ωx)
,
where:
ω
= a wobble coeffi cient
x
= the distance along the tendon.
ω
is expressed in radians/m, and has a value that normally lies between 0.005 and
0.01 for internal prestressing
5.17.3 Anchor set
Tendons are stressed by jacks that grip the tendon and react against the concrete.
When the load is transferred from the jack to the anchorage unit, there is bound to
