I have been trying to convert this Smath Studio file to Mathcad
and I have gone this far but found an error that said
"This Array index is invalid for this array."

Please comment on it.
Thanks.File not found.File not found.

Wrote

I have been trying to convert this Smath Studio file to Mathcad
and I have gone this far but found an error that said
"This Array index is invalid for this array."

Mathcad index starts 0 ... Smath 1
Your Smath document turns red Syntax is incorrect.
To be doctored ... so immense !

Wrote

have been trying to convert this Smath Studio file to Mathcad
and I have gone this far but found an error that said
"This Array index is invalid for this array."

Hello,

The SMath program you are referring was posted sometime back to the FORUM by me.
It was based on the moment distribution method, and use of it is limited only to
cases of 2 span substitute frames.

Recently, I posted a couple of examples based on the stiffness method. which can
be used for any practical number of spans.
See the following link.

https://en.smath.com/forum/yaf_postsm80558_RC-Subframe-Analysis-by-Stiffness-Method.aspx#post80558

I have redone your example using this stiffness method, attaching it with a definition file.
These two files must be in the same folder please.

Unfortunately these two sm files are lengthy, and I sincerely welcome forum members
to propose any improvements..

I am extremely sorry that I am unable to check your example Mathcad file.

Cheers,

Include_Programs-R10.sm (118 KiB) downloaded 68 time(s).
MacGinley and Choo_Ex_13.1_TO_FORUM-STIFFNESS Method.sm (387 KiB) downloaded 64 time(s).

Above example simplified to show only the Support and Column Moments.

Definition file not required.

Cheers

MacGinley and Choo_Ex_13.1_TO_FORUM-STIFFNESS Method-R1.sm (232 KiB) downloaded 70 time(s).

MacGinley and Choo_Ex_13.1_TO_FORUM-STIFFNESS Method-R1.pdf (333 KiB) downloaded 77 time(s).

Thank you.

The last example.
Cheers.

Reinforced-Concrete-Design-to-eurocode-2 Mosley Bungey Hulse-7th Ed-R10-Simple.sm (301 KiB) downloaded 89 time(s).

Reinforced-Concrete-Design-to-eurocode-2 Mosley Bungey Hulse-7th Ed-R10-Simple.pdf (435 KiB) downloaded 114 time(s).