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Ram Elements NDS Wood Design/Checking

Currently, the only code available is NDS 2005.  Since we have to submit our calculations for review, having the appropriate code check/design standard is important.  Currently in Virginia, we are required to use NDS 2015.  Some states require NDS 2018.

One of the newest, coolest hip innovations in wood design is Mass Timber.  I know Mass Timber or CLT (cross-laminated timber) is a "Hot Topic" in the press.  I'm guessing that 95% or higher of wood-framed projects DO NOT use this innovative system for framing.  So until Bentley has had a chance to add this tool, I would suggest that it would be reasonable to update the wood design capabilities and code checking from the 2005 NDS to something like 2015 and/or 2018.  As long as it is clear that this chapter of the NDS is not included, I don't think you will find much resistance.  Does this make good sense and for Bentley does it make cents?

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  • Since it's been over 3 years since I first asked for the wood design in Elements to be brought into compliance with current building codes, and this item says that you are "planning to update the NDS design code for the current RAM Elements capability for 2021" and it's now 2022, I thought I would reiterate the need for this. It's worth pointing out that since states legally adopt a model code (with amendments if desired), and that building code edition incorporates various national standards by reference (e.g. AISC 360-16, NDS 2015, etc), our calcs from Elements using the 2005 NDS standard are not in compliance with any of the state building codes.

    There are several items of concern here.

    1) Table data for wood properties are updated with each new edition and some of Elements' underlying data is obsolete now.It's hard to have good output based on outdated properties. It's also hard to trust the output from Elements when it doesn't cross-check with other wood programs that have bothered to update their data in the last 16 years....

    2) The glulam section tables don't include all of the sizes from NDS. Everything in NDS Supplement Table 1C should be available as a section size without me having to create a table of custom sizes to account for what are actually standard sizes.

    3) Elements should have the basic NDS options for glulams as options for design. Besides not having recognized sizes as noted above, Elements doesn't have the Stress Classes from NDS Supplement Table 5A, only the Combination Symbols from the expanded version of 5A. Again, these are valid choices in NDS and should be valid choices in Elements.

    3) Elements calculates several properties incorrectly because it doesn't use the correct value for Emin and hence Emin'. That affects both the Column Stability factor Cp and the Beam Stability factor CL through the critical buckling design values, FcE and FbE, respectively.

    There is certainly a lot of room for Bentley to improve in the area of wood design. There's even still room for Bentley to take the lead. If you updated to NDS 2018/2021, that would be a big start. Mass Timber is a big area right now. We worked on a 5-story mass timber building last year that had large glulam columns and beams, CLT floors, CMU stair/elevator cores for shearwalls, and a couple of steel moment frames in one area. Such a mix of materials in one project is is where Elements really shines compared to steel-only or wood-only programs. Since Ram Connection can be incorporated into Ram Elements, being able to address even some basic wood connections in our Elements models like we do for steel connections would be a very nice addition. And if you've ever used the WoodWorks Connections program, they set the bar very, very low. It wouldn't take much to surpass them in functionality, especially if it could be part of an integrated model like Ram Elements and Ram Connection allows. Just sayin'. But I'm also with SVGregory on this: don't delay release of basic wood provisions for development of mass timber provisions, because I'm a lot more likely to need correct results on a double 2x12 header than I am a CLT floor plate or shear wall. And honestly, if I can't get correct results on that double 2x12, why should I trust Bentley with calcs on a 20.5"x 41" glulam beam or 20.5" square column (a typical beam and column size on the 5-story project I mentioned)? Get the basics correct again so we can trust you there, then expand functionality.

  • Hello Jason,

    Yes, the NDS-2018 component was completed last year (2021) for saw lumber and glulam (maintaining current functionality) and now it is being implemented in RAM Elements to be released in a couple of weeks. Let us check your comments and come back to you ASAP.

  • Looking forward to it. Long overdue, especially since other software companies just take updating to the current design standards as part of doing business in the engineering software field and make it happen every single code cycle.

  • Just checking back on this regarding either your ASAP response or the overdue new release of Elements....

  • Hello Jason,

    Let us detail the answers below:

    1) Table data for wood properties are updated with each new edition and some of Elements' underlying data is obsolete now. It's hard to have good output based on outdated properties. It's also hard to trust the output from Elements when it doesn't cross-check with other wood programs that have bothered to update their data in the last 16 years....

    [Ans] We have updated the following:

    • Table 4A: Coast Sitka Spruce, Douglas Fir-Larch North, Yellow Cedar.
    • Table 4B: Minor updates.
    • Table 4C: Updated several (up to 300 items) and added several new species and grades. Also corrected the Fcp related the modulus of elasticity.
    • Table 4D: Updated and added some items from Supplement-2018.
    • Table 4F: Added Douglas Fir – France&Germany and Norway Spruce – Norway.

    2) The glulam section tables don't include all of the sizes from NDS. Everything in NDS Supplement Table 1C should be available as a section size without me having to create a table of custom sizes to account for what are actually standard sizes.

    [Ans] We have updated Table 1C sections to support 2 ½ width, 3 ½ width, 5 ½ width, 12 ¼ width. Those combined with several depths.

    3) Elements should have the basic NDS options for glulams as options for design. Besides not having recognized sizes as noted above, Elements doesn't have the Stress Classes from NDS Supplement Table 5A, only the Combination Symbols from the expanded version of 5A. Again, these are valid choices in NDS and should be valid choices in Elements.

    [Ans] This is not yet included and will be planned for a next release.

    4) Elements calculates several properties incorrectly because it doesn't use the correct value for Emin and hence Emin'. That affects both the Column Stability factor Cp and the Beam Stability factor CL through the critical buckling design values, FcE and FbE, respectively.

    [Ans] RAM Elements is currently calculating the value of Emin using equation D-4. Now for NDS-2018 we are reporting the Emin for compression and bending.

  • I can't help but notice the absence of Table 4B in your list.... Working in the Southern US, Southern Pine is huge here. In the past when I've used Elements for a wood project here, it was based on the SP entries in the glulam table, but if I were to use any dimensional lumber, it would likely be Table 4B. However, that brings up a question of workflow. Table 4B doesn't use the Size Factor like the other tables and splits out material properties by section size. It looks like your "Dimension Lumber SP" table is based on the lowest 4B values (i.e. from the 12" wide section). I get that that is the conservative route to take, but quite the penalty since there is up to a 50% increase in strength going from those entries to the smaller sections like 2x4 and 4x4. Do you have a recommended workaround for that? Would it just be to copy those entries over to a custom database split out by section size and adjust the values there manually, then pick material from that new table like "SPine_No2_2x6" for a 2x6 member, and "SPine_No2_2x8" for a 2x8 in my project? A bit tedious, but the only way around that for the user right now, it seems. Could you not do something similar and simply expand Table 4B with the Size Classification column from Table 4B added to the end of the material name and the strengths adjusted accordingly? Otherwise, I notice you do have the NDS Supplement allowance for Size Factor on specific Southern Pine case like 4" thick x 8" deep or greater. One possibility would be to keep your existing single SP material table and apply the Size Factor to that internally like you are for a #2 SP 4x8 currently. NDS can say the Table 4B incorporates the size factor already (except for exceptions listed like certain grade and sizes of 4x lumber), but Bentley could work back from that to a separate Size Factor applied to the existing 12" wide values tabulated.But then keeping the same tabular format as NDS would probably be clearer and simpler to check.

    That brings up something else that would be helpful in the output: could you list somewhere the properties being used? For instance, right now the design report lists adjustment factor values like Size Factor and Wet Service Factor for tension, compression, bending, and so on, but never lists what Ft, Fc, Fb it's using. That is listed in the Materials table view in the program, but never in the design report. That would be helpful when checking output.

    Thanks!

Comment
  • I can't help but notice the absence of Table 4B in your list.... Working in the Southern US, Southern Pine is huge here. In the past when I've used Elements for a wood project here, it was based on the SP entries in the glulam table, but if I were to use any dimensional lumber, it would likely be Table 4B. However, that brings up a question of workflow. Table 4B doesn't use the Size Factor like the other tables and splits out material properties by section size. It looks like your "Dimension Lumber SP" table is based on the lowest 4B values (i.e. from the 12" wide section). I get that that is the conservative route to take, but quite the penalty since there is up to a 50% increase in strength going from those entries to the smaller sections like 2x4 and 4x4. Do you have a recommended workaround for that? Would it just be to copy those entries over to a custom database split out by section size and adjust the values there manually, then pick material from that new table like "SPine_No2_2x6" for a 2x6 member, and "SPine_No2_2x8" for a 2x8 in my project? A bit tedious, but the only way around that for the user right now, it seems. Could you not do something similar and simply expand Table 4B with the Size Classification column from Table 4B added to the end of the material name and the strengths adjusted accordingly? Otherwise, I notice you do have the NDS Supplement allowance for Size Factor on specific Southern Pine case like 4" thick x 8" deep or greater. One possibility would be to keep your existing single SP material table and apply the Size Factor to that internally like you are for a #2 SP 4x8 currently. NDS can say the Table 4B incorporates the size factor already (except for exceptions listed like certain grade and sizes of 4x lumber), but Bentley could work back from that to a separate Size Factor applied to the existing 12" wide values tabulated.But then keeping the same tabular format as NDS would probably be clearer and simpler to check.

    That brings up something else that would be helpful in the output: could you list somewhere the properties being used? For instance, right now the design report lists adjustment factor values like Size Factor and Wet Service Factor for tension, compression, bending, and so on, but never lists what Ft, Fc, Fb it's using. That is listed in the Materials table view in the program, but never in the design report. That would be helpful when checking output.

    Thanks!

Children
  • Hello Jason,

    Table 4B is fully included with just minor updates (updated the list above), I did not include it before because I did the list based on your questions. There is no need to create different material per each size as for Table 4B we use an adjustment factor (based on the supplement values) that transform the minimum values that are displayed in the material database to the correct one according to the size. You might find the adjustment factors below. 

    C:\Program Files\Bentley\Engineering\RAM Elements\Design\Wood

    The manual also explain this in the point 13 in page 506 (pdf version). So please let us know if you need further info.

    For the properties being used for the limit states calculation, we are reporting them for both NDS-05 and now NDS-2018. However we did some changes to the terminology used to be more in agreement  with the NDS. Below and excerpt of the new NDS-2018 bending report showing the reference value.

  • Ah, OK. It was not very clear in the program what it was using since it showed a Size Factor of 1.0 in the report for most of the SP sections, and didn't list the Fb used. But that's good to know it is still getting handled internally. And that's great on the report. That makes it very clear what it's based on now.  Looking forward to the new release! Any updated ETA?

    Thanks,

    Jason

  • We are currently preparing a release candidate, if it passes all tests then by the end of the week it would be available for users.

  • We are currently preparing a release candidate and if it passes all tests then it would be available early next week.

  • Thanks for the update.  Clear output for the code checking is why I use Ram Elements at least for Steel Design.  There are those other programs that use the "black box" approach.  For Wood Design, I expect the same type output as the steel Design.  NDS has a lot of factors available to modify the basic allowable stresses!

    I am looking forward to the new Ram Elements "no black box" update.  One of the black box programs also has manufactured composites using LVL and PSL from several manufacturers.  Will Ram Elements have any of these composites?