Jump to content
TUFLOW Forum
Duck

Connecting 1D bridge to 2D

Recommended Posts

Hi, I am trying to add a bridge to a model using a 1d_nwk file but I am having issues (I usually model bridges in 2d but the preference for this model is 1d bridges)

The model is a 2D rain on grid model with only culverts and bridges modelled in 1D. I am therefore trying to connect a 1d_nwk bridge to the 2D using SX/CN lines the same way you would with a culvert.

The error I get is '1033 - No XS line data upstream of channel' between this and the only examples I can find being connect a bridge to a 1d channel line, I am not sure if you can connect a bridge as you would a culvert.

Can you connect a bridge using SX/CN lines upstream and downstream? If not is there a way around this like creating a short 10m channel leading up to the bridge? 

Share this post


Link to post
Share on other sites

Hi there, 

In short, yes it is possible to connect a 'standalone' bridge in a 1d_nwk file connected to the 2D with SX links. 

1d_nwk file with a B/BB type input (for this example i have used a B bridge type). The only attributes needed will be a unique ID, type (B), and then an US/DS inverts set at -99999. (setting the invert levels at -99999 will force tuflow to set both inverts at the lowest point on your HW table, you can enforce invert levels and use the Z flag in your SX line if the user wants this).

once you have your 1d_nwk file set up with your CN/SX links snapped to either side you just need to use the 1d_bg file to digitise lines intersecting the the 1d_nwk file. One that links to your HW table and one that links to your LC (losses table) as im using a B bridge type. the only attributes needed here will be the type of each and the source linked to the csv containing the info on the HW and LC values. 

schematisation of this below/attached:

image.png.44b56784d041ab51bdae1281b997f741.png

 

Useful pages with further helpful information:

https://wiki.tuflow.com/index.php?title=1D_Bridges

https://wiki.tuflow.com/index.php?title=TUFLOW_1D2D_SX_Advice

Also as TUFLOW looks at bridges with a length of zero (assuming short structure with little frictional influence) if you have substantially long bridges it might be worth considering changing to a culvert set up. 

 

Cheers,

Joe

 

Share this post


Link to post
Share on other sites

Hi JJStobart, thanks for the reply.

This is the method I was going for but I keep getting 'Error 1033 - No XS line data downstream of channel "XXXX". Could not interpolate cross-section properties.'

I added a 1d_xs line (the 1d_xs line was instead of the HW line, is this correct that I don't need both?) crossing the 1d_nwk line the same way as the 1d_bg in your example with a 'XZ' type.

I read in the 1d_xs in the ecf like this; 'Read GIS Table Links == xs\1d_xs...' and had it pointing to a csv with X and Z values for the river cross section through the bridge.

I can't work out why it is not liking that. Any ideas?

Also if I use BB as the bridge type does that mean I don't need a 1d_bg file with the losses?

Share this post


Link to post
Share on other sites

Hi Duck,

I'll let Joe come back on your other questions, but specifically that error 1033 is relating to TUFLOW trying to interpolate the inverts of your channels. With channels, setting inverts to -99999 asks TUFLOW to interpolate the inverts at the end of your network lines using known invert elevations from further away in your network. I'm not sure why it's doing that for your bridge, since it should be just applying the lowest from your XZ table (or HW like you had before). For the one structure then, you could stop TUFLOW trying to interpolate anything by manually setting the inverts yourself instead of going with -99999.

It may be that this only helps move TUFLOW on to a different step which might reveal some data issue elsewhere and explain the odd behaviour, so don't expect it to cure all. I might even be more worried if this fixes the thing, as it would mean bridges weren't being handled as expected!

I've just twigged it's not only trying to interpolate inverts, but the whole set of properties, so what I wrote above doesn't apply. Suggests it's not recognising the cross section data being applied, though your command looks right. Sorry, not sure what to suggest!

Hope this helps,
Peter.

Share this post


Link to post
Share on other sites

Hi Duck,

Cheers for the input Peter, always appreciated. 

I'll look into this a bit further but I'd assume as when you're modelling a bridge in a full ESTRY network it looks to the xs associated with channels to bring that to the bridge unit as a bridge effectively has a length of zero as discussed above. In that sense, having a bridge unit standalone in the 2D, I would assume it takes your invert levels (so in the case of -99999 the lowest point on your HW table) and applies this as a flat value across the bridge bed and because of this doesn't accept xs data being applied. 

BB bridges differ from B bridges in that the losses due to flow contraction and expansion, and the occurrence of pressure flow is handled automatically. The only loss coefficients required to be specified are those due to any piers, and the bridge deck when it is submerged and not under pressure flow. Further information on how losses are applied can be found in section 5.7.2.4 of the 2018 TUFLOW manual.

Cheers, 

Joe

 

Share this post


Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.


×
×
  • Create New...