Epoxying rebar into RC special moment resistant frame.

[EDCLTD]

A contractor constructing a RC Special Moment Resistant Frame structure had cut off the column rebar to short at the column/beam interface. The column’s rebars 1” dia, extends only 12” above the poured column at that joint. The original detail is for the column rebars to bend at 90 degrees (with the approved radii) and lap with the beam rebar.
Our recommendation is to demolition approximately 40” of the column to provide adequate lap length with the existing rebars in the columns and of such length that will now have the required length to lap with the beam reinforcement.
The contractor has proposed an alternative method, which entails drill and epoxy rebars into the existing columns of 2’ depth. There are 10 No Bars in the Column. The client supervisors and also the design structural engineers has strongly recommending against this, as building is located in a high seismic zone and prone to hurricane wind loads. The SMRF was selected on this bases which is specifically designed to withstand these lateral loads.
The project manager seem to be favouring the contractors proposal, has anyone ever came across dowelling and epoxy rebars in a critical section of SMRF?.

 

[hokie66]

The "design structural engineers" should have the last say, not the contractor or project manager.

 

[dcarr82775]

I wouldn't allow the epoxy. Is it possible to use a mechanical coupler to splice the bar? not sure if that is allowed in high seismic zones.

 

[ARKeng]

I agree with dcarr... epoxy sounds like a bad idea from a seismic overstrength/ductility standpoint, especially in a SPECIAL moment frame. These have lower design forces as a result of the special detailing requirements, and my general rule of thumb when you get into that is "if the code doesn't specifically allow it, and there's any question as to whether it should be allowed, don't do it".

I think there should be some mechanical splice options that would be allowed like dcarr suggested. Or maybe a weld splice could save some demolition also, but if you can get the mechanical couplers in a reasonable amount of time, those might be the way to go.

 

[EDCLTD]

Thanks for responding. Type 2 Mechanical Couplers can be used for connecting the reinforcement, however the problem with using these couplers are
1) Length of the coupler for 1” bar = 12.3” which is greater than depth of the beam
2) The diameter of the coupler for a 1” bar is 2.2” which will then reduce the cover and also interfere with the other bars if the concrete is not demolished