Reinforcement

Place and manage reinforcement bars using edge patterns, perimeter patterns, individual placement, bar wrap, and cell-tie tools. Covers cell decomposition for concave sections, D'Hondt count allocation, and the lateral-restraint check.

Overview

Reinforcement placement is central to concrete section design. ACS provides five longitudinal placement tools and two transverse tools for positioning bars and fitments within the section.

Bars are placed at their centre coordinates, and cover is measured from the nearest section edge to the outer surface of the outermost bar (including stirrup diameter). All bar positions are measured from the section coordinate origin in millimetres.

The toolbar groups tools by role:

Placement constraints

ACS enforces the following geometric constraints at the moment a bar or tendon is placed or edited:

Bar or tendon inside a void — a bar or tendon whose centre lies inside a void is refused with a clear diagnostic (#4162). The concrete stress model assumes material wherever a bar sits; placing a bar inside a subtracted void region would produce a physically meaningless result. Move the bar outside the void boundary or adjust the void geometry before placing.

Cell decomposition

Concave sections — L-shapes, T-shapes, U-shapes, and any outline with re-entrant corners — cannot be handled by a single perimeter loop. ACS automatically decomposes the section outline into convex cells using a convex decomposition algorithm. Each cell is a convex polygon whose faces map to edges of the section outline or to internal cut lines.

Cell decomposition runs automatically whenever the section outline changes. You do not need to trigger it manually. The decomposition result is used by:

• Perimeter pattern — bars can target the whole section (distributed across all cells) or a specific cell
• Cell tie — places a closed hoop exactly around one cell
• Place bar (individual) — cell picker appears for concave sections so placement targets the intended corner or face

For a convex section (rectangle, circle, regular polygon) the decomposition produces a single cell, so no cell-specific controls appear in dialogs.

Fillet-corner sections: Sections with fillet (rounded) corners — generated by the geometry editor’s fillet tool — are handled as ordinary curved outlines. The arc vertices describing each rounded corner are preserved through decomposition, so bar placement tools that target corners or faces correctly identify and follow the filleted geometry. Bars placed at a filleted corner are anchored to the arc’s nearest endpoint rather than to a sharp vertex, ensuring they move consistently when the fillet radius is adjusted.

Placement tools

The reinforcement toolbar appears above the canvas when the Reinforcement tab is active. Select a tool, then interact with the canvas to place bars.

Select tool

Click any bar to select it. Selected bars display their coordinates, diameter, and grade. Press Delete or Backspace to remove the selected bar. Drag a selected bar to reposition it (snaps to grid).

Edge pattern

Distribute bars evenly along a single edge of the section outline.

The offset is typically the cover plus stirrup diameter plus half the bar diameter. ACS computes this automatically from your cover settings.

The edge selector lists each edge with its length and geometry type. Straight edges show which face they are (e.g., “Edge 2: bottom face, 400 mm”) while curved (arc) edges show their arc length (e.g., “Edge 1: arc, 628 mm”).

Edges are numbered from 1, matching the E1, E2, … labels the canvas draws when Element numbers is enabled — so the edge you read off the drawing is the edge you select here. When you target a single cell of a concave section instead of the whole outline, the selector lists that cell’s faces (“Face 1: left face, 150 mm”); a cell’s face numbering is local to that cell and does not correspond to the canvas edge numbers, which is why each face carries its location. The targeted cell is shaded in the live preview so you can see which region of the section you are reinforcing.

:::note[Cell shading and face-location labels in pattern dialogs — September 2026 (#5823, #5828)] The bar pattern dialogs — Edge pattern, Perimeter pattern, and Place bar (individual) — now shade the targeted cell in the live canvas preview and label each cell face with its location (top, bottom, left, right). Previously, only the canvas overlay highlighted cells; the face labels were not shown in the dialog itself.

The face location appears beside each face’s length in the selector list — for example Face 1 · left face · 150 mm — so you can identify the correct face without counting vertices on the drawing. Curved faces show arc in place of a location because they do not face a single direction. The shading and labels update live as you change the targeted cell. :::

Arc edges — angle offset

When the selected edge is a curved arc (as on a circular column or curved haunch), bars are spaced by arc length rather than chord length, so the spacing is uniform around the curve. An additional Angle offset (deg along arc) input appears for arc edges:

A positive angle offset shifts the bar group counter-clockwise around the arc centre. Use this to avoid placing the first or last bar too close to the arc–straight junction.

Perimeter pattern

Place bars around the perimeter of the section at a uniform offset from the outline. Commonly used for column reinforcement.

Count modes

ACS provides three ways to specify how many bars to place:

Per edge (legacy default) — specify how many bars appear along each straight face. Corner bars are shared between adjacent faces. This mode maps directly to the original bars-per-edge behaviour and is still available for compatibility.

Total count (D’Hondt allocation) — specify a total bar count and let ACS distribute bars proportionally across the perimeter faces. Distribution uses D’Hondt proportional allocation (the same algorithm used in proportional-representation elections), which minimises the deviation between a face’s share of the perimeter and its share of the bar count. Longer faces receive more bars; no face receives fewer than its minimum geometric allocation.

Spacing — specify a target centre-to-centre spacing and ACS calculates the count per face. A minimum clear spacing between bars is enforced — if the requested spacing would produce a clear gap below the limit, ACS refuses to place bars rather than silently over-packing the face. Total count mode is clamped by the same limit.

The limit depends on the design code:

d_g is the Maximum aggregate size from the Materials tab. Under EN 1992-1-1, k₁ and k₂ are Nationally Determined Parameters — ACS applies the values the standard itself recommends, and every refusal message states the k₁, k₂ and d_g it used so a National Annex that modifies them is visible to you. If no aggregate size has been entered, ACS assumes 20 mm and says so in the refusal.

AS 3600:2018 Cl 8.1.9 states the requirement qualitatively (the spacing “shall be such that the concrete can be properly placed and compacted”) and tabulates no number, so the practice value applies. The same applies to ACI 318 and to the second-generation EN 1992-1-1:2023.

This limit governs whether bars are placed at all — it never modifies a calculated result. Bars per face mode is deliberately unclamped: you have stated a literal count.

Seeded default and its basis. The Max Spacing field opens seeded at 300 mm. The helper text beneath the field names the basis for that seed according to the active design code:

The seed is always editable. It carries no enforcement — the only floor here is the clear-spacing refusal in the table above. Changing the active design code (Materials tab) changes both the seed value’s helper text and the clear-spacing refusal floor applied at the next resolver pass.

Concave sections and cell targeting

For concave sections, the perimeter pattern uses a cell-based algorithm to place bars along the actual section perimeter, including re-entrant corners. Bars follow the true outline of each convex cell rather than a bounding-box approximation, so they sit correctly on faces that fold inward at re-entrant corners of L-, T-, and U-shaped sections.

The pattern can distribute across all cells (the default) or target a specific cell. Use Total count mode when distributing across multiple cells so the D’Hondt allocator balances the count proportionally across each cell’s perimeter length.

A cell selector appears in the dialog when the section has more than one cell. The cell you select is shaded in the live preview, so you can confirm you are reinforcing the intended leg of an L- or T-section before applying.

Circular and curved sections

When the active section is circular (or close to circular), the perimeter pattern dialog automatically adapts to place bars equi-angularly around the circular outline. The adapted inputs are:

Bars are placed at radius:

where $R$ is the section radius, $c_{cover}$ is the nominal cover, $d_{stirrup}$ is the stirrup bar diameter (or zero if no stirrups are defined), and $d_{bar}$ is the longitudinal bar diameter.

The start angle defaults to 0° (first bar at the rightmost point). Adjust it to control where bars begin around the circumference — for example, setting 90° places the first bar at the top of the column.

Clear-spacing enforcement for circular layouts. The circular perimeter dialog applies the same code-specific clear-spacing floor as the perimeter dialog. When the active design code is EN 1992-1-1:2004 and a maximum aggregate size is set in the Materials tab, the resolver enforces Cl 8.2(2) on the circular arrangement: a total bar count that would result in a clear gap below the floor is refused before placement, and the live preview reflects the feasible layout. For the practice floor (all other codes) the same check applies with the simpler max(d_bar, 25 mm) limit.

Place bar (individual)

Place a single bar at an anchored position within the section. Individual bars are tied to a section feature — a corner or a face — rather than raw coordinates, so they move correctly when the section geometry changes.

Select a placement kind:

Corner — the bar is anchored to the inside corner of a specific cell corner. The corner picker lists available corners with their cell. At reflex (inward-pointing) vertices of concave sections — inside corners where the section outline turns through more than 180° — bars are placed so their centroid stays inside the section boundary; the cover offset is measured from the enclosing edges rather than from the corner tip.

Edge ratio — the bar is placed at a fractional position along a face of the outline (0 = start vertex, 1 = end vertex). Use this for bars at a fixed proportional offset along a long face.

Edge distance — the bar is placed at a measured distance (mm along the face) from the start vertex of a chosen face.

For concave sections a cell picker appears first. Select the cell containing the corner or face you want to target, then choose the specific corner or face from the lists that update to show only targets within that cell. The selected cell is shaded in the live preview.

The face list shows each face’s indicative location alongside its length — “Edge 2 · bottom face · 600 mm” on the whole outline, “Face 3 · left face · 150 mm” within a cell — so you can pick the face you mean without counting vertices on the drawing. A curved face reads “arc” in place of a location, since it does not face one direction.

A live preview in the canvas updates as you change inputs so you can verify position before confirming.

Placement on curved faces

When the selected face is a curved arc (circular column flute, fillet corner, or arched wall face), the face ratio and face distance placement kinds measure position along the arc length rather than the chord. The bar is placed normal-inset from the arc at the resolved arc-length position, so cover is measured perpendicularly to the curved surface.

For a bar placed at arc length position $l$ on an arc of radius $R$ and half-angle $\alpha$, the Cartesian position is derived from the arc parametrisation:

Where $c_{eff} = c_{cover} + d_{stirrup} + d_{bar}/2$ is the effective cover offset and $(x_c, y_c)$ is the arc centre.

The live preview updates as you adjust the ratio or distance, so you can confirm the bar lands at the intended face position before placing.

Bar wrap

Bar wrap is a selection-first transverse tool: click the longitudinal bars the tie engages, and the number of bars you select decides which tie you get. There is nothing to choose beforehand.

The banner above the canvas keeps a running count and names the tie the current selection will produce — for example 2 bars selected → cross-tie — updating live as you add or remove bars. A third bar turns a cross-tie into a closed tie; dropping back to two turns it back.

Click Create… once at least two bars are selected. Selecting the second bar does not place the tie on its own, because that same selection may still be on its way to a closed tie — nothing is placed until you press Create….

Click a selected bar again to deselect it. Leaving the tool clears the selection.

The resulting fitment shares the diameter and grade of the current stirrup settings.

Cell tie

Cell tie places a closed hoop stirrup that exactly encloses one convex cell. The hoop follows the cell boundary at the cover offset.

The dialog behaviour depends on the section shape:

• Convex section (one cell) — a dialog opens directly. A live preview on the canvas immediately shows the hoop at the cover offset around the cell boundary. Confirm to place the hoop.
• Concave section (multiple cells) — a canvas overlay appears highlighting each cell. Click a cell to select it; the live preview updates to show the hoop for the selected cell. Confirm to place.
• Refused — if the decomposition failed for the section (for example, a degenerate outline), the tool shows an error message and cannot place a hoop.
• Ring tie bends refused — for cell ties around circular or curved cells, the hoop includes standard hook bends at the splice point. If the bend geometry cannot fit within the section at the current cover and bar size — for example, when the arc radius is too small relative to the hook extension — ACS refuses the placement and shows a message identifying the conflicting bend. Reduce the bar diameter or adjust the cover and retry.

Closure bar: The cell tie dialog includes an optional Add closure bar toggle. When enabled, a single longitudinal bar is placed at the splice/closure corner of the hoop at the same cover offset. This is useful for detailing the lap-splice end of a hoop without manually adding an individual bar. If the cell tie is placed before all longitudinal bars are present in the section, the tie’s closure anchor reference is re-derived when the remaining bars arrive — hooks are never missing because bars were added after the stirrup (#4208).

Cover violation disclosure: When any portion of the generated hoop falls closer to the section outline than the minimum cover setting — which can happen on internal shared faces where the cover boundary of two adjacent cells overlaps — ACS shows an inline warning in the cell tie confirmation dialog. The warning identifies the affected face and the minimum clear distance achieved. You can accept the hoop as-is (for example, when the face is an internal cut line with no concrete cover requirement) or adjust the cover before placing.

Cell tie is the fastest way to add a perimeter stirrup to a column or to individual cells of an L-, T-, or U-section.

Editing placed reinforcement

Every row in the Rebar/PT sidebar carries a pencil that reopens the dialog that created the item, seeded with its saved values. Saving updates the item in place rather than adding a second one, so you no longer have to delete and re-author a pattern just to change its bar count, size or grade.

Row actions run in ascending order of consequence: edit (pencil), explode (for patterns), then delete.

Because the item keeps its identity across an edit, everything attached to it survives: excluded bars, per-bar diameter overrides, tie-corner anchors, and any stirrup wrapping its bars. One edit is one undo step.

Impact warning. If an edit reduces the number of bars a pattern produces, the references pointing at the bars that disappear cannot be honoured. Before you save, the dialog names exactly what is affected — which stirrups will be withheld, and how many exclusions, diameter overrides and corner anchors will go inert. Save stays enabled: reducing a bar count is a legitimate design change and the decision is yours. Nothing is removed from the saved design either — the affected exclusions and overrides become inert rather than being deleted, so raising the bar count again brings them back.

The warning is computed from the bars the pattern actually resolves, not from a number typed into the form. This matters in Max spacing mode, where the bar count is derived from the section outline and no input field states it.

Grades that are no longer available. If a design is opened under a jurisdiction that does not offer the bar grade the item was saved with — for example an AS 3600 design opened in an ACI 318 project — ACS keeps the saved grade exactly as it is, tells you it is unavailable, and blocks Save until you choose a grade from the current list. It never silently swaps the grade for an available one: that would produce plausible numbers from a material you did not select.

:::note[SENSE 600 high-strength rebar — September 2026 (#6025, #6058)] SENSE 600 is now available as a bar grade across all placement tools — edge pattern, perimeter pattern, and individual bar placement. The diameter selector is product-aware: when SENSE 600 is chosen, the dropdown lists only the sizes registered to that product line, which differ from the sizes in the general reinforcing bar catalogue. Selecting a diameter fills the nominal bar area from the product’s own registered value rather than from the nominal-diameter formula ($\pi d^2/4$).

Results change from earlier versions for any design that previously referenced SENSE 600 bars:

• AS 3600 yield-strength policy (#6028): AS 3600:2018 Cl. 3.2.1 caps the design yield strength at $f_{sy} \leq 500\,\mathrm{MPa}$ for most provisions. SENSE 600 bars carry $f_{sy} = 500\,\mathrm{MPa}$, which is already at the cap. In prior releases the cap was applied against an assumed value above 500 MPa for certain product grades, reducing the effective $f_{sy}$ below 500 MPa in some code paths. Re-run any design using SENSE 600 bars — flexural, shear and interaction capacities may change where the cap was previously reducing the grade.
• Nominal bar area (#6033): SENSE 600 bar areas now come from the product’s registered values, which may differ from the area derived from the nominal diameter alone. Re-run designs using SENSE 600 bars to confirm the correct area is in use. :::

What editing does not change

A stirrup that already wraps a bar which no longer exists cannot be edited: its bar selection cannot be reconstructed honestly, so the pencil is disabled and the reason is shown. Restore the missing bar, or delete the stirrup and re-wrap.

Exclusion and override

Pattern-derived bars can be excluded individually or restored after exclusion. This lets you suppress bars that conflict with an opening, penetration, or cover requirement without deleting the whole pattern.

Exclude a bar — in Select mode, right-click a pattern bar and choose Exclude bar from pattern. The bar is removed from the canvas. The pattern itself remains and can still produce other bars; only this bar index is suppressed.

Restore a bar — the sidebar shows an Excluded bars section under each pattern that has at least one exclusion. Click Restore next to an individual bar to re-include it, or Restore all to clear all exclusions for that pattern.

Override position — drag a pattern bar to a new position. The bar detaches from the pattern rule at that index and holds its new position independently. The pattern continues to generate other bars at their computed positions.

Explode to bars — converts a pattern entirely to individual custom bars. This is a one-way operation: exploded bars lose their pattern association and cannot be restored to pattern control. Use this only when the pattern logic is no longer useful and you need full manual control.

Bar table

The bar table in the left panel lists every bar in the section with sortable columns:

Click a row to select the bar on the canvas. Click again to deselect. Use the Add button to create a bar with default properties, then edit its coordinates inline.

Stirrups

The stirrup panel configures transverse reinforcement for shear capacity calculations.

The panel displays the computed stirrup area:

Where $A_{bar}$ is the cross-sectional area of a single stirrup leg.

Circular fitment mandrel bend radius

For circular fitments (closed hoops placed around a circular section), ACS now enforces the minimum mandrel bend radius when computing the fitment geometry and mass.

The mandrel bend radius is the minimum radius to which the reinforcement bar can be bent, and it is a property of the bar size and grade. AS 3600:2018 Table 17.2.3.2 gives the minimum values by nominal diameter:

When the circular section is small enough that the hoop’s inner radius is less than the mandrel minimum, ACS adjusts the hoop geometry to comply — the placed bar sits on a slightly different radius than the nominal cover offset would indicate, and the computed hoop length (and therefore mass) reflects this adjustment.

Results change from earlier versions: Prior to the September 2026 release, circular fitments were placed without enforcing the mandrel radius — the geometry was computed from the cover offset alone, which could understate the bar mass for small-diameter circular sections where the mandrel limit governs (#5861). Re-run any circular fitment mass calculation if the section diameter is less than approximately 150 mm for 10 mm bars (or larger thresholds for larger bar diameters), where the mandrel minimum is likely to govern.

:::note[Circular fitments only] The mandrel enforcement applies to closed circular hoops. Rectangular cell ties, bar wraps and cross-ties are not affected — their bend geometry is computed from the corner pin, which AS 3600 Table 17.2.3.3 governs separately, and that has been enforced since the cell tie tool was introduced. :::

:::note[Circular fitment hook tails now point inward, into the confined core — September 2026 (#5954)] The hook projections on circular fitments (closed hoops on circular sections) now point inward toward the concrete core, not outward through the cover. AS 3600 Cl. 8.3.2.4 NOTE and Cl. 10.7.3.1 require that a fitment hook be anchored in the confined core — a tail terminating in the cover zone does not satisfy the clause. Before this change both hook tails pointed radially outward; on a 500 mm column with 40 mm cover they terminated approximately 0.8 mm inside the surface.

The displayed fitment geometry will change for all circular sections. No numerical re-analysis is needed — the hook direction does not affect the shear capacity calculation — but any PDF report showing the section geometry should be regenerated so the reinforcement layout is correct. :::

:::note[Circular section tie hooks and bar readout corrected — September 2026 (#5947)] Two additional fixes to circular section fitment rendering:

• Tie hook position — the seating of hook bends for circular section tie stirrups was corrected. Hooks now seat at the correct contact point on the bar, consistent with the geometry AS 3600 Cl. 8.3.2.4(a) requires.
• Cover adequacy warning — the cover adequacy warning for circular fitments now fires correctly when any part of the tie geometry falls inside the minimum cover distance. Previously the check could miss certain configurations on circular sections.
• Bar readout display — the bar count displayed in the Rebar/PT sidebar for circular fitment patterns now reflects the correct resolved count. A display-only discrepancy in the count readout has been corrected; the underlying geometry and mass calculations were unaffected. :::

Duplicate stirrup healing on load

When a design is loaded, ACS automatically collapses any stirrups that share the same ID. This condition arose from a bug in a previous version of the editor in which the pencil-edit path appended a second record sharing the original’s ID rather than replacing it (#4223). The consequential defect was invisible: the two specs were geometrically identical (same tie path, same diameter), so the only obvious symptom was that the old hook appeared not to have moved. The consequential half was that AggregateAsv summed per stirrup, so the duplicate silently doubled the shear reinforcement area in the shear tab, the batch Design Summary, and the PDF report — an un-conservative Asv that was presented without any warning (#874).

The healing rule: the last occurrence wins at the first occurrence’s index position. Appends are chronological, so the last record is the engineer’s most recent edit, and holding the original list position reproduces what a correct upsert path would have produced. The action is undoable, requires no confirmation, and an informational note identifies any IDs that were collapsed.

Lateral restraint check

The ULS tab in the right panel includes a Bar Restraint section that checks whether compression bars are adequately restrained against lateral buckling under each ULS load combination.

The check is performed per load combination and reported as an envelope across all combinations:

• A bar is flagged if it is in compression under any ULS combination and is not restrained by a fitment that satisfies the applicable clause.
• The governing combination for each flagged bar is the one that produces the most critical result.
• The envelope is the union of all flagged bars across all combinations.

Applicable clauses by member type (AS 3600):

Flagged bars are highlighted on the canvas with a red halo. The right panel lists each flagged bar by its display ID and the governing combination that produced the flag.

Skip conditions

The restraint check is skipped and the panel shows an explanatory notice when:

• Geometry unavailable — the section outline has not been defined or is invalid.
• Strain unavailable — the ULS analysis has not been run, or no load combinations are defined.
• Wall, high-strength concrete — Cl 11.7.4 restraint for walls is not yet supported for high-strength concrete grades (advisory limitation).

Fitment adequacy

Below the bar restraint list, the Fitment adequacy section checks whether the stirrup configuration satisfies the dimensional limits in AS 3600 Table 10.7.4.3 (columns):

A separate pass/fail is shown for each check. The governing spacing and diameter from the current stirrup configuration are shown alongside the limits.

Arc-seat tie-bend credit

AS 3600 Table 10.7.4.3 permits a reduction in minimum fitment diameter when the fitment bends tightly around the longitudinal bar corner — the so-called arc-seat tie-bend credit. ACS applies this credit only when the fitment genuinely wraps the bar at the arc seat: the fitment must turn the corner of the bar (i.e., the bar sits in the bend of the fitment), not merely pass alongside it on a straight leg.

In practice this means:

• Corner bars enclosed by a closed hoop or cross-tie whose hook engages the bar corner: credit is applied.
• Intermediate bars restrained by a U-bar or open stirrup whose leg runs past the bar without bending around it: credit is not applied.

If the fitment diameter fails the minimum check only because the arc-seat credit was withheld, ACS displays an explanatory note alongside the fail result. To claim the credit, use a closed hoop or a cross-tie whose standard hook terminates at the bar corner.

Prestressing tendons

For prestressed or post-tensioned sections, add tendons from the PT tab in the right panel:

See Section analysis for details on prestress loss calculations and ultimate capacity checks.

Tips and best practices

• Use the cover outline display toggle to verify that bars are placed within the allowable zone
• For circular columns, use the Perimeter pattern tool — it adapts automatically to a circular bar ring at the correct cover inset radius
• For concave sections (L, T, U shapes), use Total count mode in the perimeter pattern — D’Hondt allocation distributes bars proportionally across all cells
• For arc edges on non-circular sections, use the Edge pattern and adjust the Angle offset to prevent bars from crowding the arc endpoints
• Use Bar wrap for cross-ties and closed ties around specific bar groups; use Cell tie for a full perimeter hoop around a convex cell
• Individual bars placed with corner or face anchoring move correctly when the section outline changes — prefer anchored placement over manually editing bar coordinates
• Use Exclude (right-click) to suppress individual pattern bars around openings or penetrations without disrupting the rest of the pattern
• Check the Bar Restraint panel under ULS after placing reinforcement — flagged bars require additional fitments or modified bar positions
• Hover a row in the Cover panel to highlight the corresponding bar on the canvas and scroll it into view — useful for identifying which bar controls the governing cover
• Check minimum and maximum reinforcement ratios after placing bars — the design summary flags violations

SENSE 600 product sizes

InfraBuild SENSE 600® reinforcement (characteristic yield strength 600 MPa) is available as a product-catalogued bar size in ACS for Australian AS 3600 projects. When SENSE 600 is selected as the reinforcement grade on a section, the bar size selector in the reinforcement sidebar shows the product-registered nominal diameters and areas from the SENSE 600 catalogue — N16, N20, N24, N28, N32, N36 — rather than the generic circular idealisation $\pi d^2/4$.

Selecting SENSE 600 sizes

Each placement dialog (Edge pattern, Perimeter pattern, Circular perimeter, Place bar, Fitment) carries a Bar Material selector above its size selector. It defaults to the section’s reinforcement material from the General tab, and you can override it for that placement — the material is what determines the grade code, the yield strength and the product size catalogue together, so a bar can never hold a size from one product beside the grade of another.

With SENSE 600 selected as the Bar Material:

1. The size picker in that dialog updates to show SENSE 600 product-registered nominal diameters.
2. Sizes not published by the SENSE 600 catalogue (e.g., N10, N12) are not offered for a SENSE 600 bar — the picker lists only the certified sizes.
3. If you previously placed bars from a typed diameter that matches a SENSE 600 product size, those bars keep their diameter exactly as saved; they are not automatically converted to a product selection.

A bar saved before the Bar Material selector existed adopts the section’s material only where its recorded grade already names that material’s grade code. Anything else — a bar carrying a different grade, or a fitment recorded against a material name rather than a grade code — is shown as needing an explicit re-pick, and Save is blocked for that item until you choose one. Nothing is substituted on your behalf. The analysis applies the same rule: such a fitment earns no detailing credit for the grade it names, and the check says so rather than designing it on the section’s steel.

If a reinforcement material is removed from the catalogue while bars already reference it, those sections keep saving normally — a standing selection is not a new one, and blocking it would make every edit to that section fail with no way to clear the field. A new selection of a material this project cannot see is still refused.

Reinforcement strength policy for SENSE 600 (AS 3600 Cl. 1.1.2(d))

AS 3600 Cl. 1.1.2(d) permits reinforcing grades above 500 MPa up to 800 MPa, but caps the design strength at ULS at 600 MPa and requires the grade to declare ductility class N or E with $\varepsilon_{su} \geq 0.05$ and $R_m/R_e \geq 1.08$.

SENSE 600 bars meet these requirements and are therefore admissible in AS 3600 ULS design under ACS. The 600 MPa ceiling applies — it is the grade’s characteristic strength, not a reduction — so no capacity is lost relative to the declared $f_{sy}$. A grade at or below 500 MPa is unaffected by this rule.

Where the grade cannot be verified as meeting the ductility and ductility-class requirements, ACS refuses the analysis rather than proceeding on assumed ductility. See Section analysis § Reinforcement yield strength in ULS design models for the full rule.

Nominal bar areas for SENSE 600

Where a bar names a SENSE 600 product size, every capacity calculation uses that size’s published nominal area from the product catalogue — not the circular idealisation $\pi d^2/4$. The distinction matters because the SENSE 600 product areas are independently rounded figures and differ slightly from $\pi d^2/4$. Results change if you switch a bar from a typed diameter to the equivalent SENSE 600 product selection, or vice versa.

The product area is frozen on the bar at save time. If the catalogue row is later archived, the saved nominal area is preserved (the section is not disrupted), and the Rebar/PT sidebar discloses that the size is archived.

:::note[SENSE 600 product size catalogues available in ACS — September 2026 (#6025, #6058)] The InfraBuild SENSE 600® bar size catalogue is now available in the ACS reinforcement library. N16, N20, N24, N28, N32, and N36 product sizes appear in the bar size picker when SENSE 600 is selected as the reinforcement grade. Selecting a product size ties the bar to the SENSE 600 catalogue and uses the published nominal diameter and area for all calculations.

This is a display and selection change for new bars placed on or after this release. Existing designs are unaffected unless you explicitly re-pick the bar size to a catalogue selection, at which point the nominal area may differ fractionally from the previous circular-idealisation value. :::

:::note[AS 3600 reinforcement strength policy corrected for grades above 500 MPa — September 2026 (#6028)] The Cl. 1.1.2(d) 600 MPa ULS design ceiling was previously enforced only at the capacity computation stage and not on the admissibility gate. ACS now also refuses a grade above 500 MPa that does not declare the required ductility class (N or E), uniform elongation, and tensile-to-yield ratio, rather than letting it reach the solver and then capping its strength.

Results change for SENSE 600 sections: the admissibility gate now matches the analysis assumption, and a grade that was previously refused at the solver level is now refused earlier with a clearer message. The computed capacities for an admitted SENSE 600 grade are unchanged, because the 600 MPa ceiling already applied there. :::

:::note[Nominal bar area now uses product-registered values for SENSE 600 — September 2026 (#6033)] Where a bar or fitment names a SENSE 600 catalogue size, every capacity is now computed on that size’s published nominal area from the product catalogue. Previously, all bar areas were computed as $\pi d^2/4$ regardless of whether a product size was selected. For SENSE 600 bars the difference is up to several percent for the larger bar sizes; results change for sections where SENSE 600 catalogue sizes are selected.

No saved design moves unless you explicitly pick a SENSE 600 catalogue size for a bar. Bars saved with a typed diameter continue to use $\pi d^2/4$ as before. :::

:::note[Fitment grade resolved against grade CODE, not material name — September 2026 (#6126)] When a fitment’s reinforcement material is looked up by its recorded grade label (rather than a direct material ID), ACS now compares the label against the material’s grade code — for example, “D500N” — rather than its display name. Previously, the comparison was against the material’s display name, which caused the fitment to appear unresolvable for materials where the display name differed from the grade code, resulting in incorrect reinforcement grade resolution for those sections. Sections where the grade code and display name agree — the common case — are unaffected. Sections where they differ now resolve correctly. :::

:::note[Reinforcement dialogs now offer a material selector, not a grade-code picker — September 2026 (#6135)] The Place bar, Fitment, Edge pattern, Perimeter pattern, and Circular perimeter dialogs now present a Material selector instead of a Grade code picker. The selected material determines the grade code, yield strength, product size catalogue, and ductility class together. This aligns the dialog selection model with the rest of the reinforcement system, where materials are the primary identity. The selection is recorded at save time and takes effect in the analysis immediately. :::

:::note[Per-bar and per-fitment f_sy design basis — September 2026 (#6140)] Every longitudinal bar and every fitment now designs on the $f_{sy}$ of the reinforcement material it is placed under, rather than a single section-wide value. A mixed-grade cage — for example, plain round 250N ties with 500N longitudinal bars — is correctly designed at 250 MPa for the ties and 500 MPa for the longitudinals. This extends the per-element grade model (#6120) to the $f_{sy}$ input to the transverse strength checks. Where the fitments do not all share one $f_{sy}$, ACS uses the lowest fitment grade for all transverse capacity terms and says so in the report. Results change for sections where bars or fitments had differing grades; the Design Summary’s Reinforcement Grades table shows all grades in use. :::

:::note[Mixed-grade fitment cages: shear capacity per fitment — September 2026 (#6148)] Where the fitments do not all share one $f_{sy}$, the steel shear capacity $\phi V_{us}$ now credits each fitment’s legs at that fitment’s own grade, $\sum A_{sv,i} f_{sy,i}$. Previously every leg was credited at the lowest grade present. For example, a D500N perimeter tie beside one R250N cross-tie had its perimeter legs credited at 250 MPa. The clauses that take a single fitment $f_{sy}$ still use the lowest grade, which is the conservative value for each of them: the Cl 8.2.1.7 minimum shear reinforcement, the $k_v$ branch and its $\phi$, $\phi T_{us}$ and the Cl 10.7.4.3 minimum fitment diameter. A cage with a cell-anchored tie keeps $\phi V_{us}$ on the lowest grade too. The report states which basis each clause used. AS 3600 does not address a cage of several grades. The summation assumes every leg a shear crack crosses reaches yield, which holds for ductility-class N steel. Shear results rise for mixed-grade cages only; uniform cages are unchanged. :::

Grade 250N plain round reinforcement

AS/NZS 4671 Grade 250N plain round (R-bar) reinforcement is available in the bar material selector. Plain round bars have a smooth surface profile — lower bond to concrete than deformed bars — and AS 3600 Cl. 8.1.9.1 requires plain bars to be provided with standard hooks or cogs at their ends. Common diameters are R6, R10, and R12; Grade 250N is most frequently used for fitments and nominal reinforcement.

:::note[AS/NZS 4671 Grade 250N plain round reinforcement available — September 2026 (#6163)] Grade 250N plain round bars are now seeded in the reinforcement catalogue and available in the bar material picker for all placement tools. Previously only deformed bar grades (Grade 500N, SENSE 600) and mesh products were offered. :::

Related pages

• Section geometry — defining the concrete outline
• Materials — concrete and steel material properties
• Section analysis — running ULS and SLS checks