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Conspan "Design Truck" vs "Double Truck"

John Lynch
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I am having difficulty matching Conspan's "Double Truck" load.  The user manual (and AASHTO) states that the negative design LL should be 90% of lane + 90% of two HL93s with non varying rear axles spaced no further than 50ft.  I agree with this however when I produce my moment diagrams by hand, I do not match Conspan's Double Truck.  When I open the live load library to investigate, I see the following note attached to the Double Truck:  "NOTE: Internally CONSPAN automatically considers 80% of the truck load selected for analysis, applied simultaneously with this lane load".  This does not match the AASHTO 3.6.1.3.1.  Can you expand upon this live load case and where AASHTO talks about it?

In addition, I believe the "Design Truck" case is automatically recognizing a continuous span bridge and running the two HL93s spaced at 50ft+.  The live load library gives no indication of this but my negative moment diagrams match it.  Can you confirm my suspicions?

I should also note that I am running version V13.00.00.68.  My company has had crashing issues on new computers with v14 and we are holding out to v15 in hopes that the problem goes away.

Thank you for the help in this negative moment issue.

  • 0 Offline in reply to John Lynch
    I apologize Alex. I see what went wrong now. Thank you for your help.
  • 0 Offline in reply to Alex O [Bentley]
    Alex. I will ignore the note on the "Double Truck". Regarding AASHTO Art 3.6.1.3.1, I think we both agree on how the negative moment should be produced. However, I am also using influence lines and feel the "Design Truck" is performing this as well (not sure what the Double Truck is doing). To do another check, I created a custom vehicle to simulate the two HL93s, spaced between 50ft-300ft apart. The negative moment produced by this matches my numbers and not the "Double Truck". Would it be easier to send you the file I am working on?

    Regarding the Bridge Enterprise, is Bentley moving towards requiring this program? We don't use the entire library of programs that are offered so there is not much of an advantage of having a 'go between' program installed. If the stand alones are fading out, well thats another issue.

    With the crashing on V13, I've had my IT guys on the phone with Bentley on several different occassions with no positive results. We had Conspan placed on three brand new machines with full rights (while in ITs hands) and the crash occured consistently based on the time of the day. No one knows why but due to the energy already spent, we're waiting for the next version before upgrading.

    Thank you for all the help. John
  • 0 Offline
    John, that note regarding 80% of the truck load was the only issue in the version you are running; the program was correctly following the AASHTO Art. 3.6.1.3.1. The note you refer to was removed in v14.
    Only the 32 kip axles have a fixed spacing as per code requirement. The program is using influence lines for LL analysis. We did check in the past this loading condition with an independent program and we did not find any issue.
    Please install and use v15.0.0.41 of LEAP Bridge Enterprise where you can run CONSPAN the same as you did with the stand-alone version. The stand-alone version will get one last release with just bug fixes and no AASHTO Code updates. Transition from using component programs to using LEAP Bridge Enterprise is free. I am not aware of CONSPAN crashing; make sure you are given full control (read and write) on program folder and try to see if you get any crash while working with the tutorials of CONSPAN from your local drive.

     
    This is a test

    Answer Verified By: Dilip Matange [Bentley] 

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