Please reply to this topic to comment on or discuss Repository item:
MONORAIL.xls

In the "MONORAIL.xls" spreadsheet workbook in both calculation worksheets it was discovered that for the specific case of 2-pairs of wheels (4 wheels
total) I had inadvertently omitted the self weight of the monorail beam in the actual calculation of the strong axis bending moment, Mx. The monorail beam self weight was included in the actual moment calculation for the case of 1-pair of wheels (2 wheels total). The text displaying the formulas used for the moment were correctly shown for both cases, it was the calculation cell for that one case that was in error.

I'm somewhat puzzled at the nature of this error and how it happened, as I usually write out the logic/formula, copy that to the calculation cell, and then substitute the appropriate cell references for each of the variables in the logic/formula. I obviously must have gotten carried away with use of the backspace key during the editing process. It is updated to version 1.4.

Alex Tomanovich, P.E.
Senior Structural Engineer

In the "MONORAIL.xls" workbook, in both worksheets there was a common "typo-error" discovered. The text version display of AISC 9th Edition Equation F1-8 for allowable x-axis bending stress had the denominator show as "(Lb*12/(d/Af))" where the "/" symbol should have been a " * " symbol to read as "(Lb*12*(d/Af))". The actual calculation cell formulas were correct in all cases. Again, these were "cosmetic" errors only, but they needed to be corrected. This workbook is now version 1.5.

A couple of typo errors were pointed out to me recently in the "MONORAIL.xls" workbook.

In the text display of the formula for the x-axis simple span moment (Mx) for a concentrated load at midspan, the text had both divide and multiply symbols between the variables "Pv" and "L/4". The divide symbol should not have been there. In the resultant biaxial stress at point 1 calculation, the text display of the formula for the z-axis stress showed sigma(y), when it should have been sigma(z). These typo errors occurred in both of the calculation worksheets, and they have been corrected in version 1.6.

A potential "quirk" was found in the "MONORAIL.xls" workbook. From Table 6 (Values of Cb) on page 5-121 of the AISC 9th Edition Manual, the minimum value of the bending coefficient (Cb) is 1.0. A value of 1.0 for Cb is what is used most of the time in design, even if conservative. However, if for the cantilever portion of the monorail beam the user chooses to use the Lbo and Cbo values as determined off of the calculation page to the right per the AISC Journal Article by N.S. Tanner, then the calculated value of Cbo can be < 1.0. (The subscript "o" refers to the overhang or cantilever portion of the monorail beam.)

Specifically for the situation of a member with Lbo <= Lu and with an input value of Cbo < 1.0, the two worksheets were ignoring an input value of Cbo < 1.0, treating Cbo as if it were = 1.0, and thus deferring to Fb = 0.6*Fy. This problem involving the use of a Cbo value < 1.0 did not occur for Lbo > Lu.

Again, this potential problem would have only arisen if a value of Cbo < 1.0 was used from the Tanner article in conjunction with Lbo <= Lu.

The corrections have been made, and the updated workbook is now version 1.7.

Alex Tomanovich, P.E.

A few incorrect cell references were brought to my attention in the "MONORAIL.xls" workbook.

Off of the main calculation page to the right for the Y-axis stress ratio, the cell references in cells BB90, BB13, and BE13 were not using "fby(total)", only "fby", and thus were neglecting the stress contribution from torsion, "fwns".

Fortunately the logic statement in cell I90 on the 2nd page of the actual calculations was correct, in that it was using "fby(total)" in the calculation of the stress ratio, so the actual displayed and printed calculations were fine.

This problem occurred in both worksheets of the workbook, and I have made the corrections. The workbook is now version 1.8.