The py_RC Elastic spreadsheet (last discussed here) has been updated with a new function py_Fatigue3600, providing design for fatigue to the latest AS 3600 concrete structures code. The new spreadsheet and associated Python code can be downloaded from:

py_RC Elastic.zip

The download file includes full open-source Python code. For details of the pyxll package required to link the Python code to Excel see: https://newtonexcelbach.com/python-and-pyxll/

Input for the new py_Fatigue3600 function is as before. Note that the new function is intended for use on bridge structures, and the number of fatigue cycles is calculated to AS 5100.2 requirements, based on the current number of heavy vehicles/lane/day:

The output of both functions is shown below:

The main differences between the calculations to the two codes are:

• Different variation in the steel fatigue stress limit related to the number of stress cycles. AS 3600 has a higher stress limit for mid-range cycles, but for low cycle numbers (as in this case), or very high cycles, the AS 5100.5 stress limits are higher.
• For the concrete compressive stress limit AS 5100.5 has a conservative limit, not related to the number of cycles. AS 3600 has a procedure for calculating the number of cycles to failure for any specified compressive stress. This has been adapted in the function to calculate a stress limit for any given number of cycles. In most cases the AS 3600 limit is significantly higher than the AS 5100.5 simplified approach.

A check has been added to the spreadsheet to verify that the concrete stress limit calculated by the AS 3600 function does correspond with the required number of stress cycles: