Cable stayed bridge construction sequence

[Dakka]

Hi.

Consider a cable-stayed bridge. The side span consists of 18 segments and the midspan has (16 segments + Stitch segment + 16 segments)
The adopted construction sequence is the following:
From the Pylon, 16 segments are cast on both LHS & RHS sides, completely supported on Formwork.
Then the 8 Stay cables are stressed one after the other.
After stressing all the stay cables, the formwork is removed.
Optimization is done in this stage, by fixing the Stay cable forces to restrict the BMD of the Superstructure to a good profile.
Then the Abutment segment (Seg 17&18) of sidespan are cast thereby finishing the sidespan.
Now, the Stitch segment of Midspan is cast.
Now, the SIDL & WC are laid. This generates a Not so good BMD.
Now, Second stage prestressing is adopted for all the stay cables to acquire an optimized good BMD.

The goal of the problem statement is to decrease the Stay cable forces while still maintaining an optimized Bending moment of the Superstructure, because the Stay cable costs are very much higher. Are there any methods to optimize the Bending moment of Superstructure? Meaning which would replicate the action of stay cable force? Such as using a Ballast load in Midspan before casting stitch and removing it after stitch is cast? Or Support lowering?
(PS: Pin bearing in vertical direction is considered as support for side spans)

Thanks in advance,
Dakka

 

[SlideRuleEra]

The adopted construction sequence is...

The goal of the problem statement is to decrease the Stay cable forces while still maintaining an optimized Bending moment of the Superstructure...

Normally (but not always) adopted procedures are used because they are cost effective and provide acceptable (not necessarily optimal) results.

Before looking too deeply into possible methods to decrease the Stay cable forces (like ballast load at midspan) perform a cost-benefit analysis. Will the expense (construction schedule, labor, material, necessary equipment, interference with other construction activities) of procuring transportable size ballast, planning for then putting ballast into position, and removing it provide a significant financial or construction schedule benefit compared to the adopted sequence?
Note: Intangible results, such as making the bridge design engineer "happy", is not a significant benefit.

You very well may be right, but see if the cost is worth the (technical) benefit.