Getting Isolated Node errors and Instability (1 type)

Anonymous — Thu, 26 Nov 2020 01:22:56 GMT

Hi,

I am a student using RSA for the first time and I have constructed a pratt truss bridge simulation using a tutorial online. The bridge is in S275 steel with various different steel section members depending on the part of the bridge. I am tasked with applying weather related loads on my bridge until failure (my project is Transport Infrastructure and climate change) and I need to find out how infrastructure can be evolved to be suitable for any future drastic climate change. This means I will be using primarily the seismic, temperature, wind, and snow loads on my bridge. I've learned how to apply the loads but I am getting isolated node warnings on my bridge and my supervisor is wondering if these warnings will affect the overall outcome of the bridge if it fails due to a certain load. I've removed all the weather loads before uploading the project file for simplicity's sake but have kept the live and dead loads.

I've attached a screenshot of my results window after simulation along with the file itself. Any help would be greatly appreciated, thank you.

The bridge file currently has no loads on it apart from a live load and dead load and EN1993 combinations.

Re: Getting Isolated Node errors and Instability (1 type)

Simau — Thu, 26 Nov 2020 10:52:59 GMT

Hi @Anonymous

You can't ignore type 1 instablity, take a look at the huge displacements you'll get.

This is a workaround:

- Delete node 21

- Select all your bars and delete releases

-Select all diagonals and set them as truss

- Change supports configuration

Model attached

Re: Getting Isolated Node errors and Instability (1 type)

Anonymous — Wed, 02 Dec 2020 21:50:12 GMT

Thank you!

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Getting Isolated Node errors and Instability (1 type)

Re: Getting Isolated Node errors and Instability (1 type)

Re: Getting Isolated Node errors and Instability (1 type)