Restraint Requirement Analysis

What it does

The clear zone is the roadside strip, measured from the carriageway edge, in which an errant vehicle should be able to stop or regain control without meeting an obstacle or a dangerous slope. The norm of the active country profile defines two things about it, and the command applies both:

1. How wide it is. A base width read from a table by design speed and traffic volume, multiplied by the Kcz factor, which widens it on curves: the more, the tighter the radius and the higher the speed.
2. Whether the ground inside it calls for restraint. For every crest/toe pair found in the section, the norm gives a minimum slope as a function of the embankment height. Steeper than that, the embankment is not recoverable and restraint is indicated.

The window gathers five jobs over the same alignment and surface:

• Analysis along the alignment (7): cuts a section at every step, on both sides, and grades each side critical (restraint indicated), non-critical embankment or cut/flat. Draws the cuts in plan, produces the Excel report and the guardrail batch table.
• Clear-zone boundaries (5): draws, along the alignment, the carriageway-edge line and the clear-zone line, on both sides.
• Section at a point (23): analyses the clicked side at any station and draws the cut and, if asked, the cross section with a grid.
• Point in the clear zone (28) and interferences (29): tell whether a point, or each block of a selection, lies inside the clear zone.
• Section viewer (41): steps through the analysed sections and computes any other station with a click on the alignment.

What the alignment has to carry

The command uses the project alignment and reads three of its properties, all station-indexed:

If one of them is missing over the alignment, the command asks, before running, whether to set it now:

• Yes, total extension: asks for one value, stores it for the whole alignment, and the analysis goes on. The design speed is picked from a list of 40 to 120 km/h; the carriageway width accepts 1 to 100 m.
• Yes, segmented: opens Alignment properties to set the property by stretches. Run the analysis again afterwards.
• No: the analysis does not run.

The radius comes from the alignment's geometry at each station.

The surface

The Surface list (16) holds the drawing's Civil 3D surfaces. With more than one, <all> is offered too and analyses them all. Without Civil 3D, the surface is the project's LandXML, shown as <land xml>: the LandXML sample (40) loads one. With neither, the command asks you to select the terrain faces in the drawing (3DFACE or PolyFaceMesh).

Workflow

1. Run CAPCAD_ANALYTICS_RESTRAINT. The window opens beside the drawing. To try it without a project of your own, click LandXML (40): the sample terrain and alignment are loaded and drawn.
2. Pick the Surface (16) and check the Step (22).
3. Pick the outputs: Draw (11), Generate section reports (12), Batch guardrail report (13).
4. Click Analyse the section slopes along the alignment (7). If the alignment lacks traffic volume, speed or width, answer the question described above.
5. A progress bar follows each element of the alignment. At the end:
6. the cuts appear in plan in the verdict colours, and critical stations get the mark H = <height>;
7. with (12), Excel opens with the CRESCENTE (increasing) and DECRESCENTE (decreasing) sheets;
8. with (13), the stretch table appears in a window and the command asks whether to open the guardrail batch insertion already filled in;
9. a message sums up how many sides came out in each verdict, or warns that there are issues to check in the report.
10. Click Section viewer (41) to step through the sections and see why each station got its verdict.
11. To draw the clear-zone boundaries along the alignment, click Generate the clear-zone boundaries (5).
12. To analyse a station off the step, click Analyse the slope at a single section (23) and click beside the alignment, on the side to analyse.

The window

The numbers are the same in every figure on this page: 1 to 41 in the analysis window, 42 to 52 in the section viewer.

First tab, the window as it opens.

Tab 1

Cross slope (top left frame)

Kcz for incompatible curves

The (speed, radius) pair may not exist in the Kcz table: a tight radius at a high speed is not covered by the norm. This frame says what to do then.

With neither option and an off-table pair, the boundary generation (5) shows the pair's speed and radius and offers to open the alignment properties.

Analysis along the alignment (top right frame)

Layers of the cuts drawn in plan, all with the arrow linetype SETA_CONT_1 and lineweight 0.40:

On every critical side, a point and the text H = <embankment height> mark the toe of the slope, on the critical layer, even with Draw unticked.

Single section (bottom frame)

Footer

Tab 2: Vertical

The Vertical tab has a single button.

Tab 3: Extra

The Extra tab: neighbouring commands and the three numbers that build the guardrail stretches.

The section viewer

The viewer at a station on a curve: on the right the ground falls away and the side comes out critical, with the deciding pair in purple and "44,6% / 34,0%" (measured slope against the norm's limit); on the left the ground rises and the side comes out cut/flat. The clear zone is shaded blue on both sides. At the top, the alignment with the analysed stations.

The viewer does not write to the drawing. It shows the whole section, from one clear-zone limit to the other across the carriageway, and colours the judged stretch of each side on top of it.

The bar between the alignment and the section can be dragged to give more room to one or the other. The section takes the same mouse as the alignment: dragging with the left button draws a zoom window. With the cursor over the section, the footer shows the offset, the elevation and the distance to that side's edge.

The colours:

How the options combine

The figures below came out of real runs of the analysis over synthetic terrain, at vertical exaggeration 2. A 7 m carriageway (edge at 3.50 m), design speed 100 km/h, traffic volume 3,000: 8 m of clear zone on each side.

The labels inside the figures are in Portuguese: esquerda is left, direita is right, corte/plano is cut/flat, aterro ok is a non-critical embankment and crítico is critical.

The three verdicts

A 60 % slope starting 2.50 m beyond the edge. The crest sits at the edge itself, so the flat shoulder counts towards the horizontal run: the crest/toe pair accumulates a 3.00 m drop over 7.50 m, that is 40 % average slope, not the 60 % of the slope face. The limit the table gives for a 3.00 m drop is below that, so the side comes out critical.

The same terrain at 25 %. The drop reaches 1.375 m over an 8.00 m run, that is 17.2 % average slope, far under what the table asks for at that height: there is an embankment, there is no criticality.

Terrain rising to the right: there is no drop at all inside the clear zone, and the side comes out cut/flat. The left side is flat in all three figures and comes out cut/flat in all three.

How the restraint limit behaves

The table applied is a step function: the higher the embankment, the gentler the slope that already makes it critical. It starts at the lowest height the table covers and levels off at 1V:3H from a certain height upwards. Below the lowest row there is no line at all: that is the shallow embankment waived by option 10.

The comparison is strict: a slope exactly equal to the limit does not call for restraint.

How the clear-zone width behaves

The base width is read from a table by design speed and traffic volume, then multiplied by the curve factor. Two properties of that lookup decide whether you get an answer:

• The speed must be one of the table's rows. A design speed between two rows finds no width: the station is flagged in the report, and on a tangent the clear zone comes out zero.
• The radius is fitted onto a table row before the lookup. Below the tightest row and from the widest row upwards it counts as a tangent, and the curve factor is 1.

The final width is curve factor × base width.

From critical stations to guardrail stretches

Each critical station covers from its own station to the next station of the step; contiguous ones become a single stretch. Stretches separated by a gap smaller than gapTolerance (35) join, and each stretch gains extensaoExtra (37) at both ends. In the figure, tolerance 40 m and extra 8 m.

Each stretch becomes one row of the table. With Use km (15):

Km ini · Km fim · Afastamento · Ação · Bloco entrada · Bloco saída · Terminal entrada · Terminal saída · Bordo ini · Bordo fim · ZL ini · ZL fim · Cor talude

Without it, the first two columns become E ini · N ini · E fim · N fim.

Ação (action), Bloco entrada/saída (entry/exit block) and Terminal entrada/saída come out as ?: the analysis knows where restraint is needed, not which guardrail nor which terminal. You complete those columns in the batch insertion and draw. Cor talude carries vermelho (red) for a stretch with any critical station and laranja (orange) for a stretch of non-critical embankment only (option 14).

Remembered between sessions

When it closes, the window stores the controls of three frames: the analysis-along-the-alignment frame (8 to 16), the Kcz method and its value (17 to 19) and the single-section frame (24 to 27).

The viewer stores the exaggeration, the grid and the clear-zone limits.

Notes

• Overlapping surfaces. With more than one surface, each section uses the first one that covers the cut.
• The judged section stops at the clear-zone limit. Terrain drawn beyond it is there so you can see the slope continue.
• The guardrail side. The sign of each row's Afastamento states the side: positive on the right, negative on the left, looking in the stationing direction.
• The command has no keyboard shortcut. ZL is the shortcut of CAPCAD_MARKING_AREA_LINEAR.