Why can't SSA compute correct link slope?

[cs32691]

SSA can't seem to compute the correct slope between junction to node (my network has several occurrences of this).  The junction and node elevations are given, link offsets are zero... it ought to take the vertical difference between adjacent junctions/nodes and divide by the linear distance between them but for some reason reports zero link slope, which leads to overflow at several nodes.  I don't see an obvious solution... anyone?

[Matt_Haokip]

Hi,

You may want to attach your SSA model so that we can review it and comment on it.

Thanks,

[cs32691]

Right, here it is, renamed as a .txt file

[Matt_Haokip]

Thank yo for the file. Slope in SSA is computed from the difference between the Inlet & Outlet inverts of the pipes divided by the pipe's length shown in ft/ft or percentage. 

There are some issues with your pipe connectivities, especially between the Inlets to Junctions. First the flow direction appears to be in the opposite direction and secondly one the pipes inlet/outlet invets are at negative inverts i.e. below the the invert of the nodes/inlets. Please refer to the image in the screen capture: http://screencast.com/t/nzLNsvJLXN  

Here is how the profile for one of those pipe looks like: http://screencast.com/t/wRke4prBK 

There are more of the same issue in the whole network so, you may want to review the connectivities. If all your pipes are connected at the bottom of the Junction and Inlets, the simplest way to correct this is as follow:

1. From the Plan View | Right click and select Display Options | Select to display flow direction as follow: http://screencast.com/t/vtVuCxZhT 
2. Look at your pipes flow direction in the plan view and change the flow direction by Right clicking the pipe and selecting Reverse Direction
3. Now, Go to Project Options | Change the Elevation Type to Elevation from Depth | Click OK
4. Double click any one of the pipes to open the property dialog box | Scroll through the pipes | Click the pipe in concern |
5. Then Click the arrow < at the end of the Inlet or Outlet Invert elevation to match the inverts as shown here: http://screencast.com/t/6puvhqg6wbg 

I understand this is a bit lengthy process, but hope it helps.

Thanks,

[cs32691]

Thanks Matt it seems to be working.

Getting the flow arrows was a big help visually and beats scrolling through a dialog box.  Followed your advice about the change from depth to elevation and it seems to have stopped the program from arbitrarily changing inlet and outlet offsets which I had set to zero... though I don't know why/how.  

Why didn't I do this from the outset?  I only picked up the program a few weeks ago, though I've used other hydraulic apps.  Perhaps the program isn't as intuitive as it might be and I missed something as I only learned it by reading the manual, admittedly from an earlier version.  I note that several others in the civil section have tried and abandoned using the program.  Maybe I got lost in the options and missed "something". I didn't pick up the flow arrows thing until you told me, but there it is.