Expansion Joint Gap input

I want to know what is the meaning of Gaps input in Autopipe for Expansion joint tie rod?

What does a forward or a backward gap signifies?

Is forward gap always mean for tension purpose and backward for compression?

As I have heard, there will always be small gap in the tie rod for rotation in transverse direction. So, does this mean I have to input small gap always?

I tried to look at the help section of Autopipe but could not find definite answer.

Thank you

  • Hello Dipesh,

    Please remember that there are 3 supports in AutoPIPE that have a forward / back gap setting:

    Incline, Line Stop, and Tie link.

    Incline and Tie Link support

    Specify a gap forward to enable the supported point to move toward the connected to point established by the defined bearing spring direction (cosines), without generating a restraining reaction until the gap is closed. Specify a gap backward to enable the supported point to move away from the connected to point without generating a restraining reaction until the gap is closed.

    Line stop support

    Specify a gap forward to enable the supported point to move in a forward segment direction (local+x) without generating a restraining reaction until the gap is closed. Specify a gap backward to enable the supported point to move in the opposite direction (local-x) without generating a restraining reaction until the gap is closed. A large gap can be specified in order to model a one-way restraint.

    Regards,

    Mike Dattilio
    Bentley Product Advantage Group Analyst
    AutoPIPE Product Line Bentley Systems, Inc.
    ===================================================

    YouTube- Bentley Pipe Stress - Subscribe

    AutoPIPE On-Demand Training CLICK HERE
    ===================================================

    Answer Verified By: Dipesh Khadka 

  • Thank you very much for the reply.
    I can understand about it much better now.
    Does the tie link support have one end fixed and only other end moving if the gap is specified?
    Is the "connected to" point position fixed?
    Normally an expansion joint with limit rod have some gaps at both ends to allow compression or tension as necessary, so is there way to model this in Autopipe?
  • Hello Dipesh,

    The support is not rigid at either end. The gap shared by both node points.
    Example, actual limit rod has 1 inches gap both sides to expand, dialog setting gap = 2 inches.

    Regards,

    Mike Dattilio
    Bentley Product Advantage Group Analyst
    AutoPIPE Product Line Bentley Systems, Inc.
    ===================================================

    Answer Verified By: Dipesh Khadka