The py_UMom spreadsheet has been updated with further revisions to the py_OptShearCap3600 function. The new version can be downloaded from:

py_UMom.zip

For more information on the other functions in the spreadsheet see: py_UMom spreadsheet and OptShearCap3600 function.

The changes to the py_OptShearCap 3600 function are:

• There is a new option to calculate the longitudinal force due to shear using the AS 5100.5 equation, with all other calculations to AS 3600.
• The input has been modified so that axial force, moment, shear and torsion are specified for the critical load case, and a range of M/V (moment/shear ratio) values are entered to generate the interaction diagram.
• The option to adjust axial load has been removed. The input axial load will be applied to all load cases.

The revised input and typical output is shown in the screenshots below:

Examples comparing the different longitudinal force options with different levels of shear reinforcement are shown below. The 4 options in each graph are:

• Longitudinal shear force to AS 3600 with no adjustment of the compression strut angle, Theta.
• As above with the compression strut adjusted to minimise the longitudinal shear force.
• Longitudinal shear force to AS 5100.5 with the vertical force in the shear steel, Vus, limited to V*.
• As above with no limit to Vus.

The first case has shear reinforcement just adequate for the input V*:

Increasing the shear reinforcement greatly increases the shear range with unconservative unreduced bending capacity when the AS 5100 calculation is used with no limit on Vus:

When the shear reinforcement is reduced below the level required for the input shear force the critical forces are all in the range where shear capacity governs the failure mode, and all four options give the same shear capacity: