Segmental bridges erected by balanced cantilever method:

[steveyeung]

Does any experienced bridge engineer can give me a clue how the creep changes the bending moment diagram:

For a newly erected segmental bridge, the moments over the interior supports are maximum and hogging and zero moment at the mid-span (in theory),However, as the time elapses with the continuity tendons in place and the effects of the creep, sagging moment will appear in the mid-span regions.

The final moment diagram will reside somewhere between the BM envelope of the simple cantilever and that of the bridge assumed being constructed on falsework.

My question is, for the initial design purposes, who long the mid-span region will be under the sagging moment region?

 

[Alekk]

Well, I'm not an experienced engineer but I hope this can help: for preliminary design you can see
Schlaich-Scheef, Concrete box-girder bridges, IABSE-AIPC-IVBH, ETH Honggerberg - Zurich 1982 , pg. 47-48-49.
For final design you should run a non-linear time-depemdemt analisys; anyway using simplified methods you can expect about 10%-15% errors (for dead load).

Greetings

Ale