Course · lesson 1 of 6

Reading and drawing reinforced concrete

A reinforced concrete drawing tells the fixer where every bar goes; the bending schedule tells the yard what to cut. This lesson reads both: views and sections, line conventions, bar callouts and marks, range lines and layers, and the schedule columns, with the STATIX project schedule.

1. Learning outcomes

After this lesson you can:

find your way round a set of RC drawings: plans, elevations, sections and the schedule;
read the line and bar conventions and a bar callout;
explain bar marks and count bars over a range;
read slab layers and the dimensions of a bent bar;
turn a detail into schedule rows and check them in STATIX.

2. Before you start

RC Design 1, lesson 8 (cover, anchorage, laps and a first schedule).
Your copy of SANS 282, and the project schedule.
About 40 minutes.

3. The drawing set

From design to site. The engineer sizes the members and the steel; the detail drawing shows where every bar goes; the bending schedule (SANS 282) tells the yard what to cut and bend; the fixer builds the cage from both. The drawing and the schedule must agree bar for bar.

Views. A plan looks down, an elevation looks from the side, and a section cuts through the member where a section mark (a letter and an arrow for the viewing direction) says. A beam is usually shown in elevation with one or more sections; a slab in plan.

4. Conventions

Line and bar conventions. The concrete is drawn thin so the steel stands out: bars along the view as thick lines, bars cut by the section as solid dots, links as thick closed lines with their hooks. Many offices draw the steel in a colour; the weight of the line is what matters on a print.

The bar callout. Each group of bars on a drawing carries a label: how many, the steel type and size, the bar mark, and the spacing where the bars are spread out. This order is common South African practice rather than a code rule; whatever the office uses, every drawing must use it the same way.

Bar marks. Every distinct bar (its shape, size and dimensions) gets its own mark, and the same mark appears on the drawing and in the schedule. Two bars that differ in anything need different marks. STATIX gives one mark per distinct bar and numbers them 1, 2, 3 and so on.

5. Counting and layers

Range lines. A slab or a wall has many identical bars, so only one or two are drawn, with a range line showing where the group starts and stops. The number of bars over a width w at spacing s is the width divided by the spacing, rounded down, plus one (a bar at each end), which is how STATIX counts them.

Reading a beam. The elevation shows where the bars run and stop and where the links are spaced; the section shows how many bars sit in each layer and where. Read them together: a bar that appears in the elevation must be counted in the section, with the same mark.

Slab layers. In plan a slab's bars are shown by their direction with a layer label: B1 for the outer bottom layer, B2 for the one above it, T1 and T2 at the top (common practice). The short-span bars usually go in the outer layer, where they get the most depth.

bars over a width w at spacing s: n = floor(w / s) + 1 cutting length: the shape code's length from the outside dimensions, rounded UP to the nearest 50 mm (SANS 282 cl. 3.5) mass: n × length × kg/m (πd²/4 × 7 850 kg/m³)

6. Bent bars and the schedule

Dimensions of a bent bar. SANS 282 gives a bar's leg dimensions to the outside of the bends (cl. 4.1.1), so the cage fits inside the cover. The yard works out the cutting length from them; the drawing and the schedule give only the legs.

The schedule's columns, as the STATIX project schedule lays them out: member, bar mark, type and size, number of members, number in each, total, length each (the cutting length), shape code, shape, the dimensions A to E (or r), and the mass.

7. In STATIX

In STATIX: every concrete calculator can send its bars to the project schedule; the project board gathers the sheets and the schedule, with the order list, the cutting list and DXF; and STATIX 2D details and schedules inside AutoCAD. Lesson 6 follows the whole path.