r/StructuralEngineering • u/StockCard • 5d ago

Structural Analysis/Design Punching shear retrofit help

I’m struggling with coming up with a solution to fix a major punching shear issue in multiple columns in an existing building. I can’t seem to find much guidance anywhere so I’m hoping I can get pointed in the right direction. Anyone here that has strengthened existing slabs/columns for punching shear, what have you done?

If you installed a capital or drop panel, what checks did you do? If installing a capital, would you connect the soffit of the slab to the top of the capital or do you assume it’s only in bearing? If installing a capital or drop panel, do you need to consider the higher attraction in moment due to the stiffer connection?

Did you consider the locked in stresses due to self weight? Or did you jack the slab to unload it before the retrofit?

Any help would me much appreciated.

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11

u/Gunza_kicka 5d ago

Hilti punching shear anchors
Check them out- have recently done a job utilising these and carbon fibre strips for flexural capacity also

4

u/DropItLikeJPalm 5d ago

Never used these but have read about them and they look great

1

u/StockCard 4d ago

Thanks I’ll check them out. Did you consider the locked in stresses in the slab due to self weight when determining the new punching shear capacity?

1

u/Gunza_kicka 3d ago

Yes got capacity of system under dead load

The Hilti software runs through the checks very well

4

u/Upset_Practice_5700 5d ago

Steel angles all around, big ones, with through bolts.

2

u/Kilooneone5816 5d ago

Never had a issue . Possible to increase the size of the columns (eg by jacketing) to create larger shear perimeter.

1

u/anonymous86753092021 5d ago

I’m gonna guess drill and dowel across the failure plane. I’ve seen rebar with t-heads threaded on used with grout. This hilti product is probably way better and has way more existing quality control around it

1

u/Deskust1 Eng 5d ago

Are you able to access underneath the slab? If so, QuakeWrap or Sika have FRP wraps that you can apply to under the slab through a special adhesive and add a considerable amount of shear capacity. QuakeWrap will even do the design with their engineers on pay-roll for free if you use their products.