huangyhg

structural steel/concrete
i have 3 concrete 'pillars' 760mm square about 2-2.5m high.
4 mechanical structures of appox. 1 tonne and with large moving parts (100rpm) is to be placed on these structures with m20 chemical bolts (6) all at least 175mm from edge.
i am thinking we should increase the size of pillar to around 1000mm sq. with new concrete, but old structure is around 50 years old.
i know old and new concrete will not 'fix' to each other but should a 250mm 'casing' supply enough support?
are there likely to be other problems encountered?
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your problem should be more descriptive.
i could not visualize it.
may be you can explain the problem with more details
thanks.
tjb, yekta,
i think the placement of 4 mech. structures on these three rcc columns is important too. isn't it yekta? 50 years old structure is not a matter at all. is there a platform? 760 sq. pillar of 2-2.5 m height is not slender. its a short column. tell us more about reinforcement tjb.
shenoy.
tjb
on the face of it your problem appears to come down to placing a 125mm thick outer skin on your column if i visualise it correctly. are you then asking if the new concrete casing will separate under load from the older column core?
if so then why not view the interface as a construction joint. the connection would require the old column to be scabbled on all faces and probably primed with an adhesive. your detailing of the reinforcement in the casing, especially the links would need to comply with the detailing rules from the appropriate design code as you analyse the new and old columns as one section. you would probably also need to drill and grout the main bars into the base slab at the foot of the column to give sufficient anchorage.
regards
ginger
there's not enough information in your description of the problem to make an engineering recommendation. however, consider demolishing the columns and rebuilding them, if you can. it would probably be less expensive in the long run and there would be fewer unknowns.

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