Compound Curve -Spiral-Curve-Spiral-Curve-Spiral in OpenRoads

Hi 

Did you tired this option ? 

Under Geometry ribbon 

1) Arc from Element - Spiral arc from element 

Once you draw this element then you can use Arc between elements , the first element can be Spiral arc from element and the second element can be line 

Thanks 

Anurag 

The problem with this method is that the spiral between the two arcs is a full spiral.  That is, the starting radius is infinite with an ending radius of the second arc.  There is no smooth transition between the first arc and the middle spiral.  The purpose of the middle spiral is to transition from the radius of the first arc to the radius of the second arc.  It needs to be a spiral segment, where the starting radius matches the radius of the first curve and the ending radius matching the radius of the second curve.  ORD is particularly bad in its support for spiral segments.

I have found only one reliable method for creating this type of geometry that does not require the use of a calculator.  Unfortunately, it is limited in its application.  And, as seems to by design, tweaking the curve to get the right fit requires tearing it apart and recreating it from scratch.

The necessary inputs are the incoming and outgoing tangents and a point on the curve.  The point can be the TS, the ST or a point on one of the arcs; a point in one of the spirals won't work.  And, of course, the curve radii and spiral lengths or constants.

Start at the end of the curve with the known point.  If the known point is the TS or ST, use Spiral Arc From Element.  If the known point is a point on the arc, use Spiral Arc To Element.  This curve set will include a full spiral and one of the arcs.

The next step uses Complex Transition Between Any Element And Arc.  The "Back Spiral" is the one attached to the tangent.

The two curve sets will almost certainly go in opposite directions so you will want to transpose the backward curve before complexing it into an alignment.

ORD treats these as two distinct curve sets, so edits can be quite challenging.

I would really like someone from Bentley come up with workflows to create these curves with different inputs and result in a spiral segment between the arcs.  There were several methods for creating this geometry in InRoads, but Bentley has yet to acknowledge this gap in ORD.  Not that replacing functions found in earlier software should be considered enhancement but requirement.  This requirement is currently unfulfilled.

Please refer to the attached video showing Spiral Arc from Element creating a compound spiral between the two arcs using OpenRoads Designer 2021 Release 2 (version 10.10.21.04)

This solution does not include the exit spiral (or tangent) and it requires knowledge of the CS at the end of the first arc rather than a pass-through point on the curve.  It does create a spiral segment but its use will be quite limited.

The image found in a previous post (https://communities.bentley.com/products/road___site_design/f/geopak-inroads-mx-openroads-forum/143177/compound-curves-with-spiral-segments) shows a typical situation faced by our surveyors.  This is a realignment of the highway constructed about 70 years ago.  In preparation for a new project we need to survey the section of highway, recover any surviving monuments and resolve the alignment to fit the monuments as best as possible.  It is not unusual to recover monuments defining only the tangents (which don't match the record bearings) and a point in a spiral.  Resolution of this problem will most likely require several iterations to find the best fit.  InRoads SS2 provided some powerful and flexible tools to work through this resolution.  ORD seems to be particularly unsuited to this type of work.

The previous video was just to show that the radii on the compound spiral are correct. Sprial Line from element can be used to complete an SCSCS in that case.

It's understood that the InRoads Horizontal Curve Set tool is not available in OpenRoads. Here is another possible workflow that may be helpful in the meantime that allows definition of a curve through a point.

Yes, that's a helpful video for the method I described above.

The lack of the geometry tools available in InRoads, or similar tools, is what is so frustrating.  Especially after 10  (11?) updates and ORD is still missing capabilities that were available for, literally, decades in previous software.

Can you not create it with InRoads and then import into Open Roads Disaster?  That is our current workflow for all alignments due to ORD being garbage.

Can you not create it with InRoads and then import into Open Roads Disaster?  That is our current workflow for all alignments due to ORD being garbage.

Of course you can... until you can't.  Who knows when InRoads will no longer work or when the agency will no longer want to deal with the licensing hassles or network issues or hardware issues.  We can only hope that Bentley produces a suitable replacement before we lose InRoads altogether.