Continuing from: Frame Analysis with Excel – 6; Beam end releases and actions

Download Frame4.zip – the download file includes complete open source code.

Two more refinements have been added to the frame analysis spreadsheet:

- The stiffness matrix has been revised to take account of shear deflections for members where the shear area and shear modulus are provided.
- It is now possible to apply displacements and/or rotations to supports. Fixed freedoms are specified with “F”, or enter the support deflection in the appropriate units, or rotation in radians.

In addition a plotting routine has been added to plot the frame, with or without scaled deflections.

Shown below are results for an example frames, with results from the same frames analysed in Strand7, and plots of the deflected shape (scaled by a factor of 20) from the spreadsheet and Strand7:

Frame4 output compared with Strand7; click to view full size.

Spreadsheet plot of deformed shape x 20

Strand7 deformed shape

Truss input and output added 30 Jan 10:

Member end releases are specified by entering a 1 in the column for the freedom to be released. A truss can be modelled by releasing the rotational freedom at both ends of each truss member (M1 and M2). Input and results for a simple truss are shown below. Note that all the members have zero moment at both ends, and the rotations (in radians) at each end of each beam are reported. The end release table headings in the spreadsheets in Frame4.zip have been modified to clarify the reqired input.

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As a suggestion, you may improve your algorithm by making it working with trapezoid loads. Of course, it will be appreciated if you keep us on your news list. Thanks and best wishes.

Regards

RH

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RH – it does work with trapezoidal loads, see some of the earlier posts for examples. I will also be adding more examples later, and (eventually) there should be a feature to plot applied loads.

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Is there a limit on the number of Nodes an Beams? I am trying to run the program with 28 Nodes and 27 Beams and the program is crashing. I get the following error message: Run-time error ‘6’: Overflow.

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DH – there isn’t a specific limit. It is limited by available memory, but 28 nodes shouldn’t be a problem.

If you would like to e-mail your file to my gmail account (dougaj4) I will have a look at it.

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How do you release the moment at the ends of members? For example how would i run the program assuming everything is a truss? I see the beam end releases in the input spreadsheet can you give me an example for how to use this?

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DH – I have added some comments and an example of a simple truss to the post.

Please let me know if anything is not clear.

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Do you have copy writer for so good articles? If so please give me contacts, because this really rocks!🙂

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Another feature that would be benificial is spring supports.

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DH – you can always insert a member as a spring support of course, but yes, a specific spring support feature would be useful. I’ll add it to the “to do” list.

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I tried to run a modified version of the worksheet that accompanies the revision 1.06 (1/30/2010) and it gave me errors (run time error 13). The only modification done to the original worksheet (If I am correct the input file that accompanies the web version is a truss) was the elimination of the end release to all of the elements (I erased the ones in the worksheet). Doing this and if I don’t missed something you will have a frame therefore it should not give me any error. I am doing something wrong? Could you post additional information in the site clarifying this issue?

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Daniel – Thanks for the feedback. Could you e-mail a copy of your file to dougaj4@gmail.com please.

I downloaded the file from the link in this post and erased all the end releases, and it seems to work OK.

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Sorry for wasting your time Doug, but playing longer with the input file I found the mistake. My mistake was that if you have a frame system (there are not number ones in the release cells) therefore the column with the beams numbers should be empty too. In my trial I erased the numbers ones but not the column with the beam numbers. To avoid this in the future I added in the worksheet cell that counts the number of beams with releases (number 4 in the internet input file) an “if”. This “if” checks if the number of releases are 0, then it set the number of beams with releases to 0 too. It also checks that the numbers of end releases are bigger than the number of beams with releases. I know that there are alternatives more efficient but I did not want to modify your program.

Thanks again Doug four your time and for providing as with this very useful educational tool.

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Daniel – no problems, I’m glad you found a solution and I certainly prefer to hear about problems rather than have people encounter something that doesn’t work and discard the program.

Handling the number of items better (including number of nodes and number of beams) is on my “to do” list, but your modification is ceratinly an improvement.

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Hi Doug,

Are you planning to extend to examine a frame which is a combination of Arch and straight beams?

Regards,

Susant

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Susan – I don’t have any immediate plans for curved beams, but you can model an arch as a series of short straight beams.

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your program is way so good! it works so well on frame analysis.

I tried to use lateral point loads on frame connections to simulate an earthquake or a wind load. Is it possible to do so?

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Napster – yes, you enter loads on the Input2 sheet. You can either apply distributed loads to vertical members, or point loads to any point on any member, but in either case specify the load direction as X.

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it sounds odd, I’m not sure if I was wrong with the inputs. nodal loads are applied as X direction but when my colleagues tried to check them, the results are different? Is it OK if ill send you a file of the data input?

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napster – sure, send to dougaj4 at gmail and I’ll look at it as soon as I have some free time.

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Hi Doug,

I have been “playing” with the Frame_4 file, have question on distributed loads.

if a beam element is on an inclined orientation and is subjected to a distributed load Perpendicular to its longitudinal axis, would this load have to be resolved into global X and Y components then input in the file??? That is, if the direction of the load is neither along X nor along Y.

if such loads are resolved along the two X and Y directions would the code still calculate the fixed end moments…etc, ??

Thank you

FM

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FM – in short, yes and yes.

I have uploaded a simple example with a portal frame to:

http://cid-275d981e8a790dad.office.live.com/browse.aspx/BlogFiles

You should be able to open the file in Excel direct from that address, or download it as a zip file.

Please let me know if you have any problems.

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Follow up..

the reason for my last post is that the “write up” in the file states that the distributed loads must be in X or Y directions, ” Distributed and point load direction is either “X” (horizontal) or “Y” (vertical)” on sheet “Input 2”

thank you

FM

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Hi Doug.

Didi you have some 3D analisys?

Regards.

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Davi – I will post something on 3D at some time, but it’s not in my immediate plans at the moment.

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Great,

thanks.

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