huangyhg

stripping concrete post from form
gentlemen,
have a question on the best option to remove an h-beam stlye full concrete post from a prestress bed.
stat's
each post is tensioned to 31,000lbs (8 total cables) the dimensions of these posts are 12"x21" and up to 28' long. these posts are cast with the groove for the "h" facing up and down. the only way to pull these posts out is straight up.
what are my options to do this? i've considered probably 3 or 4 lifting lugs in the center of the post (which is attached to prestress cables are rebar) and using an i-beam with (4) hook on it that is long enough to reach these 3 or 4 lugs and pull it straight up and out with our crane. these are all cast indoors and we are using cresent 880voc release agent.
thanks!
are the the vertical wall forms stationary or can they pivot out of the way? can you drill holes in the steel base of the casting bed for insertion of compressed air nozzles? the total load of these posts is less than 7 kips, so the moment realized by lifting at l/5 and 4l/5 is not producing too much bending force if you can break the adhesion of the form. use steam to cure to 5500 psi. (pca cylinders under the cover to match field cure strength)
the walls are fixed in place, however, your idea of the compressed air is very intriguing. i will probably look into this idea. i think what it comes down to is making sure our release agent is applied correctly to aid in breaking the bond. thanks for the suggestions, we will be pouring a test block tommorow and i'll utilize the l/5 and 4l/5 dimensions.
look up precast and tilt-up concreete lifting and see if there are any principals from that that you can use.

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