Shearheads, Shearheads, Rolly Polly Shearheads 1

I am having a crisis with a flat slab design that I am working on. Shear Stud Rails (my preferred solution) are proving inadequate to withstand the punching shear caused by the high axial loads and unbalanced moments. I have seen other engineering drawings that use I-beams as shearheads. I am unconvinced that these are ductile enough to do the job properly. In this case seismic is not an issue.



In my design code (CSA 23.3, I am Canadian!) the following reference is made: The design of shearheads shall be based on the concepts in the ACI Committee 318 Building Code Requirements for Reinforced Concrete (ACI 318M-89) and Commentary (ACI 318 RM-89)pp351.

I don't know much about the ACI. I also hate when codes refer to other codes when they shouldn't. But that's beside the point.



Question: Has anyone ever used shearheads made of I-beams, and what was the design procedure. The above ACI reference, does anyone know what this is, and how I might make use of it?

 

[Imagineer]

I don't have the 89 version of ACI-318 but I do have the 99 version.&nbsp;&nbsp;I think the applicable section is section 11.9 Special Provisions for brackets and corbels.&nbsp;&nbsp;Its only a couple of pages but it's too long to type here.&nbsp;&nbsp;If you email me your fax #, then I'll fax it to you.<br><br> <p> Imagineer<br><a href=mailto: > </a><br><a href= > </a><br>

 

[daveross]

If you can get hold of ACI318M-95, section 11.12.4 et sec gives guidance on design of shearheads using steel I sections and also traditional stirrup reinforcement. I have never used the I section solution, and would be concerned about&nbsp;&nbsp;displacing the column reinforcement and getting the column concrete around the steel section.This will require close supervision on site to make sure there are no mistakes.&nbsp;&nbsp;If the columns are heavily reinforced, I wouldn't go for this solution!!!<br><br>You could look to the British Standard BS8110 Section 3.7 which gives an alternative method of providing punching shear reinforcement, however it is more conservative than the ACI, and you will end up with more reinforcement.<br><br>Alternatively, it might be safer&nbsp;&nbsp;to increase the depth of the drop panel around the columns if the shear forces and out of balance moments are high.<br><br>If you e-mail your fax# I will send you some photocopy extracts of some relevant literature. Good Luck !!!!

 

Thanks for your responses. <br>I can't find a link to email you. Do I need to be a member?<br>MM

 

[Imagineer]

Oops,<br>&nbsp;&nbsp;Thought my email appeared in the info on me.&nbsp;&nbsp;Click my nick.<br><br> <p> Imagineer<br><a href=mailto: > </a><br><a href= > </a><br>

 

[daveross]

Same response as Imagineer !!!!!<br><br>Regards,<br><br>Daveross

 

[DENIRO]

what about column head or drop pannels ?...they both work <br>i suggest column head specially u mentioned that heavy reinforcement....and if u think about drop pannel u should take care of the depth