Two Overhang Beam with UDL

Two Overhang Beam with UDL - Moment diagram Problem - Messages

#1 Posted: 2 years ago
yoswos

yoswos

0 likes in 6 posts.

Group: User

I have attached a mathcad file.. and the moment diagram at the end doesn't match
with expcted output.. it should have gone smoothly to end with x coordinate 5m.
but at certain point it has jumped to postive rigion.

Please help fix it.
Thanks

File not found.File not found.
#2 Posted: 2 years ago
overlord

overlord

554 likes in 1333 posts.

Group: Moderator

I have no idea why mathcad plots that segment faulty.
But it is possible to plot correct graphic in SMath.
However SMath integration is not very good and fast.
It will take much more time than mathcad, and zig-zagy.
You can improve plot by increasing Integrate: Accuracy.
It is in Tools>Options>Calculation.

Regards

PS: I increased accuracy to 500 to get a decent plot.
It took 50 seconds to plot in the picture!!
Integration should really be improved.

UDL.sm (18 KiB) downloaded 59 time(s).

2023-02-20_22-50.png
#3 Posted: 2 years ago
Martin Kraska

Martin Kraska

1222 likes in 2150 posts.

Group: Moderator

In the interactive handbook you can find examples for beam analysis.

They use symbolic integration and equation solving with Maxima. This is very fast, except for the Maxima restart at the beginning of the sheet (can be removed if all works well).

Show Spoiler



example maxima beam.sm (41 KiB) downloaded 58 time(s).
Martin Kraska Pre-configured portable distribution of SMath Studio: https://en.smath.info/wiki/SMath%20with%20Plugins.ashx
#4 Posted: 2 years ago
yoswos

yoswos

0 likes in 6 posts.

Group: User

Sorry but I have problem again

with M(5m)=-0.2083 kN m
it should have been
M(5m)=0
#5 Posted: 2 years ago
yoswos

yoswos

0 likes in 6 posts.

Group: User

Wrote

Sorry but I have problem again

with M(5m)=-0.2083 kN m
it should have been
M(5m)=0




My sorry it is correct.. since it is overhang it should have moment at the end;;

#6 Posted: 2 years ago
overlord

overlord

554 likes in 1333 posts.

Group: Moderator

Though it should be smaller. Probably zero by the way.
Result can be reduced with integral accuracy set to 10000.
SMath integral algorithms are not good enough.

Regards

2023-02-21_08-45.png
#7 Posted: 2 years ago
Alvaro Diaz Falconi

Alvaro Diaz Falconi

992 likes in 1675 posts.

Group: User

Hi. Remembering that solving an ODE is also told to integrate it:


UDL.sm (22 KiB) downloaded 55 time(s).

int.png

The domain can also be restricted to M(x) by multiplying it by the corresponding inequalities.

Best regards.
Alvaro.
2 users liked this post
#8 Posted: 2 years ago
Jean Giraud

Jean Giraud

983 likes in 6866 posts.

Group: User

Wrote

My sorry it is correct.. since it is overhang it should have moment at the end;;


Finite Differences [FD] is a very good yardstick insensitive to noise.
It that what you mean moment at the end ?
Cheers ... Jean.

Page2 FD.sm (57 KiB) downloaded 40 time(s).
#9 Posted: 2 years ago
overlord

overlord

554 likes in 1333 posts.

Group: Moderator

Wrote

Hi. Remembering that solving an ODE is also told to integrate it:
The domain can also be restricted to M(x) by multiplying it by the corresponding inequalities.

Best regards.
Alvaro.


This is a marvelous solution.
I learned a new thing today.
Thanks Razonar.

Maybe I am wrong but I think formula should be like this.
Huge kN*m values appear if calculated as in the picture above.

Regards

2023-02-21_17-24.png
1 users liked this post
#10 Posted: 2 years ago
Jean Giraud

Jean Giraud

983 likes in 6866 posts.

Group: User

ODE integrator(s) range from exact [rarely]
approx. 4 decimals ... to glorious freak !
64 bits Smath does not have 32 bits Matlab ODE.
Recently checked on my PC2 this damned bug.
Cheers ... Jean.

ODE 0 TEST [17].sm (45 KiB) downloaded 43 time(s).

Revisit from few months ago.
#11 Posted: 2 years ago
Alvaro Diaz Falconi

Alvaro Diaz Falconi

992 likes in 1675 posts.

Group: User

Wrote

Maybe I am wrong but I think formula should be like this.
Huge kN*m values appear if calculated as in the picture above ...



Hi overlord. You're absolutely right. Thanks for catching that error. Only 3 orders of magnitude. Who could worry about that? The Mathcad block can also be used, although I don't know if this is the best way to deal with the units, using an intermediate function Mo.

int.png

UDL.sm (26 KiB) downloaded 51 time(s).

Best regards.
Alvaro.
  • New Posts New Posts
  • No New Posts No New Posts