Weakening shear walls

[D2008R]

I sometimes work in demolition. As part of the preparation for explosive work in concrete shearwalls it is common for contractors to remove the heavy reinforcement stiffeners at ends and corners in order to allow drills to perforate the walls longitudinally.

I have seen situations where the design structural engineer assumed the drill would pass between heavy bar on the end of a shear wall, but it would not, so the contractor on the job just cut them out.

Since there are no longer any stiffeners should the walls be analyzed as columns regarding their vertical buckling resistance. All the plate theory applications I can find assume that at least one side will be clamped or pinned, but in this instance both sides are free. Can someone guide me to a reference for this condition?

 

[ishvaaag]

If I understand you well (I am not familiar with demolition practice) even with the corners cut of core shearwalls you still count with the relative bracing provided through the floor coming from the orthogonal remnants of the as built core shearwall. So each shearwall segment should be calculated in the new situation with P-Delta, reduced stiffnes as proper, and beam-column check for p-small delta between the floors, assuming the overall P-Delta check remains satisfactory.

 

[tadeng]

The walls most likely span vertically from floor to floor. The heavy reinforcement in the ends/corners is to take the tension/compression in the shearwall. I assume you are checking to make sure the wall will not fall once the end rebar is cut. It would still be able to span from floor to floor, but its function as a shearwall will be basically eliminated.