Using slipform in tower construction 2

[mnsameti]

Hi everybody, I am supervisor of a reinforced concrete tower, the
contractor uses slipform as formwork of all the vertical elements
like shear walls, core walls and columns, it can not pour concrete
more than one floor height in one time casting because of installing
stirrups and other horizontal steel bars through it and some other difficulties .I think the
construction is not proceeding at a good pace and maybe it is better
to use slipform only for walls. I will appreciate if you tell me your experience about the issue.

 

[MiketheEngineer]

If memory serves - one floor a week is pretty good. Remember, the concrete will not be at full strength in seven days. THAT MUST considered.

 

[chicopee]

I am not sure if a jump form system is similar to a slip form system, however, if it is you may want to do a search of the Willow Island,W.V. cooling tower collapse which killed many construction workers. A scaffolding lost its anchors on the recently poured concrete. The report indicated that concrete had not been timely cured.

 

[MiketheEngineer]

Yes that was the basic cause at Willow Island BUT there was NO engineer heading up that portion of the project. Some foreman was calling the shots.....

 

[hokie66]

Not sure of the details of your building, but slip form is not very practical for columns, as you have discovered. The floor concrete needs to be cast monolithically through the junction with the columns.

 

[mnsameti]

Thank you hokie66 for your comments . The floors concrete casting
have been monolithic with columns by installing pull out bars in the forms of columns . The reasons of using slip form ( for contractor)
is the low cost of slip form in the area and the big dimensions of columns (about 80*220 cm.), but when it casts concrete only for one floor height it acts like jumping form and the difficulties of horizontal steel bars (relating to slip form)are exist.Thanks for your next comments.

 

[hokie66]

For big columns like that, they are really more like walls than the typical smaller columns I was thinking about. So pullout bars from rebates are feasible in some cases. It depends a lot on the size of the bars in the slab, as bending out large bars is not allowable or practical.