Prestressed/post-tensioned concrete bridges - Computational Analysis and Design of Bridge Structures - page 170

50

Distance from the left support of side span (m)

500

0 100 200 300 400

0

-50

-100

-150

One year after completion
Tensioning presetting tondons
Two years after completion
ree years after completion
Ten years after completion
irty years after completion
Figure 5.52 Increment of deflections of the bridge after completion with the presetting
internal tendons.

-200

-250

50

Distance from the left support of side span (m)

0 100 200 300 400 500

0

−50

−100

One year after completion
Two years after completion
ree years after completion
Ten years after completion
irty years after completion

−150

−200

−250

Figure 5.53 Increment of deflections of the bridge after completion without the presetting
internal tendons.

With respect to the preparatory external tendons, according to the field
observation, the external tendons were designed to be tensioned when the
deflection or stress status was about to exceed the prediction value. After
tensioning the three couples of external tendons, the upward deflection at
midspan will be 14 mm. Also, it will provide an increment of 3.5 MPa nor-
mal compressive stress in the bottom slab and a 0.4 MPa normal compres-
sive stress in the top slab.