antique flexicore planks repair 1

[johndeng]

We have a recent project which we found the antique flexicore planks made in the 60’s need repair. The old style plank is not like prestressed plank nowadays. They are made of blocks that are held together with reinforcing steel that appear grouted in place. Reinforcing steels located in the bottom chord are rotten in some places with cracks along the line. Also there are some local cracks on the top face. Please see attached pictures, and any recommendations for the repair?
My first think is to fill cores solid with light weight concrete and reinforcing bars. But it will be too heavy.
We feel the cracks are mainly due to the age, the original tendon is still good, so we just wish we can find some kind od expansive foaming to fill cores up.


Thanks

 

[johndeng]

plank section

 

[johndeng]

Original section

 

[hokie66]

Your second post shows nothing.

I would guess that what is shown in your photograph is not the same as shown in the "original section". The photograph shows modular masonry, while the section shows precast planks. Not the same, and I speculate that the construction was changed from the design.

You spoke of both "rotten" reinforcing steel and origial tendons that are still good. Hard to picture from that description.

This may be old stuff, but some of us will take exception to the 1960's being called "antique".

 

[johndeng]

Hokie66,
The section is actually real. From the section, each core shows a block section, it doesn't show the two tendons which hold a string of blocks full length.
I have more pictures which may help. I want to find some expansive foaming if anyone knows about.
Thanks

 

[johndeng]

one more pic

 

[hokie66]

Not sure of a few things: 1) Where are the tendons in section, and what are they made of?; 2) How were the reinforcing bars placed and grouted, and what size were they?; 3) What good would foam do?

 

[johndeng]

Tendons are similar to regular planks, located near bottom of ribs. I guess they are regular bars.
Just want to use foam to fill up the cores to make solid bearing, and prevent new crackings on the top plank surface. We will also seal and touch up existing cracks.

 

[hokie66]

Maybe someone else can explain how these panels are reinforced, i.e. how the bars were placed in the "blocks" and grouted in. I don't see any indication on the original drawing which you posted which shows this information.

I don't see how foam helps...looks to me like that is just covering up the problem. It doesn't provide "solid bearing".