Posted on 03/16/2018 8:55:54 AM PDT by Navy Patriot
concrete does not dry, it cures
the post tensioning like reinforcing steel gives bending strength and has been around a very long time quite successfully.
“I have never heard of tensioning concrete after it is dry enough to put in place.”
post-tensioning concrete is a very standard technique:
https://www.google.com/search?q=post+tensioning+concrete
I now see that it is used. Drying vs curing.
Potato Po tahto.
If the concrete walkway is meant to be supported by a column under that carries through to a height where cables are attached from, why wouldn’t these be in place before tensioning? This entire thing reeks of missed steps. If I am “getting this correctly” they would lift in the center of the span, while tightening the ends to cause a crown. Why not use a structure underneath that would both support and lift, adding safety and shortening the process? The support was planned, why not put it in place first?
You do not see what is taking place. The column or support at the end with the tower was in fact in place. That is the raised columns or supports for both ends were in place and the long precast post tensioned bridge element was lifted, swung into place and positioned exactly. The short precast post tensioned element has not yet been delivered and is unseen.
There is a similar but shorter element across the canal to be brought in and placed. You have seen but one of the two spans and it is supported at both ends. The socalled center support is actually there and supports one end of both of the spans. It will also be the base for the yet to be constructed column/tower to which the suspension cables will be attached.
In order to allow for placement and fine maneuvering, the central cable supporting tower was to be constructed after placement of the two spans.
In my opinion, the post tension cables inside the bridge section were tightened to produce a camber or upward curvature such that when in place and loaded, it will flatten out. For reference, look at any empty flatbed 18 wheeler and see the camber that is not there when the trailer is loaded.
The bridge spans are designed to be self supporting across the span there were no missed steps.
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