proportional longitudinal reinforcement due to

[Anonymous]

Hi,

I have a quick question regarding the output from the section design on longitudinal steel requirement due to shear and torsion for AS5100.5. I did a simple rectangular reinforced concrete beam design with some applied forces (flexure Mx, shear Vx and Torsion Mz).

From the shear and Torsion calculation, the output for proportional longitudinal reinforcement on flexure compression side shows the Fc* (the design force in the compressive zone due to flexure and axial actions) is zero. Is that correct?  Shouldn't the compression due to flexure moment able to reduce some of these longitudinal force from torsion? 

[dave_geeves]

Hi,

I have done a little research on this but I do not have access to AS5100.5:2017 so it is a little difficult (I have the 2004 version but the shear calculations changed a lot with the new version).  I have tried searching the internet for some technical papers that may give me a clue but I'm not having much luck.

I will ask a few contacts that I have  to see if I can get an answer for you.  Hopefully the developers will also see this post and comment accordingly.

Thanks for raising this point and including screenshots and data files as this helps so much.

I will get back to you soon.

Kind regards

Dave Geeves

[Anonymous]

Hi Dave,
The AS5100:2017 has changed a lot since the 2004 version especially on Shear and Torsion, which the current code is based on modified compression field theory (similar to those in AASHTO or Canadian code).
I have attached part print on shear and Torsion for your reference. The relevant clauses are 8.2.7 (which I think the axial component is missing) and 8.2.8.
Regards,
Kenneth

[Anonymous]

Hi Dave,
I have tried sending part print of the AS5100.5 on shear but not sure whether have you received it.
I have further questions regarding the section design on Shear and Torsion.
Based on the AS5100.5 and program definition on the torsional moment parameters,
The Acp = the total area enclosed by outside perimeter of concrete section and
Aoh = area enclosed by the centre of closed transverse torsional reinforcement.
However, the program set the Acp = Aoh as default, is there any reason why?
Please see attachment for further explanations.
Regards,
Kenneth

[simon_hooper]

Hi Kenneth

This is fixed in 2022.1 which is now available for download.

Thanks

Simon