Reinforcement

Place and manage reinforcement bars using individual placement, edge patterns, perimeter patterns, linear rows, circular rings, and rectangular grids.

Overview

Reinforcement placement is central to concrete section design. ACS provides seven placement tools for positioning reinforcement bars within the section, plus a stirrup configuration panel for shear reinforcement. All bar positions are measured from the section coordinate origin in millimetres.

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).

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).

Place bar

Click anywhere inside the section to place a single bar at that location. Set the bar diameter and grade before clicking. Use this for individual bars in non-standard positions.

Edge pattern

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

Input	Description	Units
Edge	Which edge to place bars along	—
Number of bars	Total bars along the edge	—
Bar diameter	Nominal bar size	mm
Grade	Reinforcement grade	—
Offset	Distance from edge to bar centres	mm

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

Perimeter pattern

Place bars around the perimeter of a rectangular region inside the section. Commonly used for column reinforcement.

Input	Description	Units
Spacing	Centre-to-centre distance between adjacent bars	mm
Corner bars	Include bars at corners	—
Bar diameter	Nominal bar size	mm
Grade	Reinforcement grade	—

The rectangular region is inset from the section edges by the cover distance.

Linear row

Place evenly-spaced bars between two points. Useful for intermediate layers of reinforcement.

Input	Description	Units
Start point	$(x_1, y_1)$ coordinates	mm
End point	$(x_2, y_2)$ coordinates	mm
Number of bars	Total bars including endpoints	—
Bar diameter	Nominal bar size	mm
Grade	Reinforcement grade	—

The spacing between bars is calculated automatically as the distance between start and end divided by $(n - 1)$ .

Circular ring

Arrange bars in a circle at a specified centre and radius. Used for circular column reinforcement.

Input	Description	Units
Centre	$(x, y)$ coordinates of ring centre	mm
Radius	Distance from centre to bar centres	mm
Number of bars	Total bars around the ring	—
Start angle	Angle of first bar from horizontal	degrees
Bar diameter	Nominal bar size	mm
Grade	Reinforcement grade	—

Rectangular grid

Place bars in a grid pattern within a rectangular area. Useful for slabs or wide sections.

Input	Description	Units
Bounds	Rectangle defining the grid area	mm
X spacing	Horizontal centre-to-centre distance	mm
Y spacing	Vertical centre-to-centre distance	mm
Bar diameter	Nominal bar size	mm
Grade	Reinforcement grade	—

Bar table

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

Column	Description	Editable
ID	Sequential bar identifier	No
Group	Placement group (edge, ring, etc.)	No
X	Horizontal position (mm)	Yes
Y	Vertical position (mm)	Yes
Diameter	Bar size (mm)	Yes
Grade	Steel grade label	Yes

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.

Input	Description	Units	Default
Diameter	Stirrup bar size	mm	10
Number of legs	Vertical legs crossing the shear plane	—	2
Spacing	Centre-to-centre along the member	mm	200
Grade	Stirrup steel grade	—	Same as rebar grade

The panel displays the computed stirrup area:

A_{sv} = n_{legs} \times A_{bar}

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

Prestressing tendons

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

Input	Description	Units
X, Y	Tendon centroid position	mm
Strand type	7-wire strand designation (12.7, 15.2, 15.7 mm)	—
Number of strands	Strands in the tendon	—
Initial stress	Jacking stress ( $f_{pi}$ )	MPa
Bond type	Bonded or unbonded	—

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
Place corner bars first using the perimeter pattern, then fill edges as needed
For beam sections, the bottom tension reinforcement typically governs the flexural capacity
Check minimum and maximum reinforcement ratios after placing bars — the design summary flags violations
Group bars logically (e.g., all bottom bars in one edge pattern) for easier editing later

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