strengthing of existing rc columns

huangyhg

strengthing of existing rc columns
i would like to know the methods of strengthing of existing rc columns excluding cfrp method.
thanks
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one way is to drill and epoxy ties into the existing column. add verticals doweled and epoxied to the foundation and the beam above. add concrete section to column by poured in place methods or shotcreting.
adding prestressing bands around the column or a steel jacket will give have the effect of increasing f'c due to confinement.
regards,
qshake
eng-tips forums:real solutions for real problems really quick.
for bridge repairs in florida, we often use reinforced concrete jackets (6" to 9" thick).  this is because of severe section loss, though.  also, sesmic resistance is not a consideration.
if your goal is just increasing axial capacity, concrete alone might work (compression only). surface prep and a good bonding agent are a must. once bending starts, the tensile faces will be in trouble.
regards,   raf
use an extreeme amount of caution when specifying any bonding agent.  i personally try to avoid any procedure that uses more than ssd preparation (surface saturated dry).  any bonding agent has to be used in a near-perfect manner or it is useless.  any bonding agent applied in an abusive (read: incompetent) manner by a contractor will become a bond breaker.
cheers,
ys
b.eng (carleton)
working in new zealand, thinking of my snow covered home...
in response to the previous email about bonding agents, remember that using cfrp in this instance (axial load capacity increase) is not "bond critical" - it is strictly for confinement and as long as the cfrp layers are lapped sufficiently, this fix will be effective regardless of bond to the concrete.  however, a sufficient bond is required for durability of the system.  i realize that the original question involved fixes outside of cfrp, but i suggest using fiberglass frp - it will require more layers of material but the fiberglass is close to 6 times less expensive than the cfrp.  the fyfe company can help with this design and concept.