Two Overhang Beam with UDL - Moment diagram Problem Options  Email this topic  Watch this topic  Print this topic » Normal Threaded

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yoswos		#1 Posted : 20 February 2023 17:33:13(UTC)
Rank: Newbie Groups: Registered Joined: 20/02/2023(UTC) Posts: 6		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 00Two Overhang Beam with UDL.xmcd (645kb) downloaded 7 time(s).
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overlord		#2 Posted : 20 February 2023 23:05:51(UTC)
Rank: Advanced Member Groups: Registered Joined: 23/07/2013(UTC) Posts: 1,129 Was thanked: 510 time(s) in 340 post(s)		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 (19kb) downloaded 20 time(s).
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mkraska		#3 Posted : 21 February 2023 00:14:20(UTC)
Rank: Advanced Member Groups: Registered Joined: 15/04/2012(UTC) Posts: 1,988 Was thanked: 1127 time(s) in 723 post(s)		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). example maxima beam.sm (42kb) downloaded 10 time(s).
		Martin Kraska Pre-configured portable distribution of SMath Studio: https://smath.com/wiki/SMath_with_Plugins.ashx
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yoswos		#4 Posted : 21 February 2023 08:35:40(UTC)
Rank: Newbie Groups: Registered Joined: 20/02/2023(UTC) Posts: 6		Sorry but I have problem again with M(5m)=-0.2083 kN m it should have been M(5m)=0
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yoswos		#5 Posted : 21 February 2023 08:42:21(UTC)
Rank: Newbie Groups: Registered Joined: 20/02/2023(UTC) Posts: 6		Originally Posted by: yoswos 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;;
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overlord		#6 Posted : 21 February 2023 08:49:22(UTC)
Rank: Advanced Member Groups: Registered Joined: 23/07/2013(UTC) Posts: 1,129 Was thanked: 510 time(s) in 340 post(s)		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
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Razonar		#7 Posted : 21 February 2023 10:46:08(UTC)
Rank: Advanced Member Groups: Registered Joined: 28/08/2014(UTC) Posts: 1,365 Was thanked: 824 time(s) in 522 post(s)		Hi. Remembering that solving an ODE is also told to integrate it: UDL.sm (23kb) downloaded 11 time(s). The domain can also be restricted to M(x) by multiplying it by the corresponding inequalities. Best regards. Alvaro. Edited by user 21 February 2023 11:08:57(UTC)  | Reason: Update the ode solver.
2 users thanked Razonar for this useful post.		on 21/02/2023(UTC),  on 21/02/2023(UTC)
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Jean Giraud		#8 Posted : 21 February 2023 16:02:18(UTC)
Rank: Guest Groups: Registered Joined: 04/07/2015(UTC) Posts: 6,866 Was thanked: 981 time(s) in 809 post(s)		Originally Posted by: yoswos 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 (58kb) downloaded 3 time(s).
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overlord		#9 Posted : 21 February 2023 17:29:30(UTC)
Rank: Advanced Member Groups: Registered Joined: 23/07/2013(UTC) Posts: 1,129 Was thanked: 510 time(s) in 340 post(s)		Originally Posted by: Razonar 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
1 user thanked overlord for this useful post.		on 21/02/2023(UTC)
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Jean Giraud		#10 Posted : 21 February 2023 18:55:20(UTC)
Rank: Guest Groups: Registered Joined: 04/07/2015(UTC) Posts: 6,866 Was thanked: 981 time(s) in 809 post(s)		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 (46kb) downloaded 2 time(s). Revisit from few months ago.
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Razonar		#11 Posted : 21 February 2023 20:51:56(UTC)
Rank: Advanced Member Groups: Registered Joined: 28/08/2014(UTC) Posts: 1,365 Was thanked: 824 time(s) in 522 post(s)		Originally Posted by: overlord 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. UDL.sm (27kb) downloaded 12 time(s). Best regards. Alvaro.
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