Effective Depth in rectangular section

[Anonymous]

Hi,

I wanna ask why the effective depth, in some cases, will lager than the section depth which provide incorrect shear capacity of the section. A simple model is attached for your reference. 

In 1st model section width = 3500mm; section depth = 3500mm

In 2nd model section width = 4500mm; section depth = 4500mm

I tried to redraw the section from 0,0 (no line drawn in negative zone).  Then it can provide correct eff. d at y-axis but problem is still occurring at z-axis.

[dave_geeves · Accepted solution]

Hi Matthew,

This is obviously not correct but it seems to have been corrected in the 2020 version of ASBD.  I tried running it in 2018 and 2019 and got the same answer as you but when I ran it in 2020 version I got an effective depth of 3372.45mm.  This seems about right considering that this is to the centre of force from all the tension reinforcement.

So you will need to upgrade to the 2020 version to enable for this calculation to automatically calculate the correct "d".  However, you can enter a value of "d" into the shear parameters (Set Parameters for: on the analysis form) to override the default value so that the calculations are done correctly.

I hope this has helped and if this has answered your question then please mark my reply as a solution so that others may benefit.

Thanks

Kind regards

Dave Geeves

[Anonymous]

I feel so upset that our company has no budget to upgrade 2020 version.

[dave_geeves]

I Matthew,

I'm sorry to hear that you are unable to upgrade.  As I previously mentioned, you can enter a value of "d" or, as you seem to have found yourself, you can redefine the section in the positive quadrant which seems to give the correct answer for me for shear directions in both the y and z directions.  Good luck

Kind regards

Dave Geeves