Double Shear Stirrup Vertical Leg Transverse Spacing Requirements 1

[bridgeengineer2007]

Does anyone know of any requirements or specifications in AASHTO or ACI regarding the minimum spacing between legs of double vertical stirrups in a cap or beam for shear design? I'm referring to the spacing across the width of the member, not the longitudinal spacing. For wide beams, it seems that you'd want to maintain a minimum spacing of where the double stirrups overlap, but I can't find any code reference indicating this...

 

[Agent666]

KootK,

Must be a regional difference. I've yet to see a plain round bar used as a stirrup in a newbuild outside of, perhaps, welded wire fabric setups.

Plain round stirrups are used in NZ almost exclusively. It's been that way since the dark ages.

'm having trouble visualizing the purpose for which you'd be using those legs in a beam-column connection. Can you elaborate. I could probably get behind using the smaller stirrup, partial width legs for shear friction given the right shear plan and proportions.

This is the paper on which the provisions were based, probably explains it better than I would, in particular the design provisions they recommended which eventually made it into the local concrete code as recommendations are on page 256.

https://engineervsheep.com

 

[KootK]

@Agent: thanks for the paper. I've posted the relevant bit below for anyone else that might be curious about it. And I'm curious, would you be willing to count such partial depth stirrups as being effective for resisting regular beam shear as shown in the second sketch below? That question arises here from time to time. Intuitively, I think that we all feel that partial depth stirrups should add something to a beams shear capacity. We typically take the hard line approach, however, of only counting stirrups that connect the center of beam tension to the center of beam compression (ish).

 

[Agent666]

I guess the research was geared towards beam-column joints specifically where the horizontal and vertical shears and the resulting strut and tie model maybe has some differences. Also column stirrups tend to be required to be closer spaced, meaning in some instances it is almost impossible to not have your shear failure going through at least some of these partial depth stirrups.

Can you say the same for beams. For a beam depending on geometry this may not be the case unless you have the stirrup sets at quite close centres.

But fundamentally there is some merit in the right situations to potentially considering something out of the part depth stirrups.

https://engineervsheep.com