Lesson 3 of 6
Turn spacing into a steel quantity
Count stirrups over a clear span, then calculate total length, unit weight and kilograms of steel.
This builds on Lesson 2, where we worked out the complete stirrup cutting-length chain — go back to Lesson 2.
- 1Turn spacing into a count
- 2Repeat the whole member
- 3Convert total length into steel weight
- 4Your turn
Learn · Part 1
Turn spacing into a count
Choose a spacing. Closer centres mean more stirrups.
100mm centres
41 bars per beam
floor(4000 / 100) + 1 = 41. This course places the first bar at the start of the clear span; the drawing governs actual offsets and zones.
- Total bars
- 123
- Steel
- 59.28kg
150mm centres
27 bars per beam
floor(4000 / 150) + 1 = 27. This course places the first bar at the start of the clear span; the drawing governs actual offsets and zones.
- Total bars
- 81
- Steel
- 39.04kg
200mm centres
21 bars per beam
floor(4000 / 200) + 1 = 21. This course places the first bar at the start of the clear span; the drawing governs actual offsets and zones.
- Total bars
- 63
- Steel
- 30.36kg
Learn · Part 2
Repeat the whole member
Reset to 150mm centres. Keep bars per member separate from the number of members.
1 beam
27 bars total
27 bars × 1 beams = 27 bars. 27 × 1220 / 1000 = 32.94m.
- Total length
- 32.94m
3 beams
81 bars total
27 bars × 3 beams = 81 bars. 81 × 1220 / 1000 = 98.82m.
- Total length
- 98.82m
Learn · Part 3
Convert total length into steel weight
Use the same 8mm bar and all three beams.
Unit weight
0.4 kg per metre
Nominal unit weight = d² / 162. Keep the unrounded value in the calculation.
All stirrups
39.04 kg
98.82m × the unrounded unit weight = 39.04kg. This excludes main bars and wastage.
Apply what you learned
Your turn.
Change spacing to 100mm over one 4,000mm clear span. How many stirrups?
See the worked solution
floor(4000 / 100) + 1 = 41 bars.
Answer: 41 bars.
Lesson notes & reference
Worked exampleAt 150mm centres, there are 27 stirrups per beam and 81 across 3 beams.
Your starting point
Carry forward the 1,220mm cutting length from Lesson 2 and apply it to three 4,000mm beam spans.
Read the complete lesson
1. Turn spacing into a count
Choose a spacing. Closer centres mean more stirrups.
100mm centres · 41 bars per beam
floor(4000 / 100) + 1 = 41. This course places the first bar at the start of the clear span; the drawing governs actual offsets and zones.
- Total bars
- 123
- Steel
- 59.28kg
150mm centres · 27 bars per beam
floor(4000 / 150) + 1 = 27. This course places the first bar at the start of the clear span; the drawing governs actual offsets and zones.
- Total bars
- 81
- Steel
- 39.04kg
200mm centres · 21 bars per beam
floor(4000 / 200) + 1 = 21. This course places the first bar at the start of the clear span; the drawing governs actual offsets and zones.
- Total bars
- 63
- Steel
- 30.36kg
2. Repeat the whole member
Reset to 150mm centres. Keep bars per member separate from the number of members.
1 beam · 27 bars total
27 bars × 1 beams = 27 bars. 27 × 1220 / 1000 = 32.94m.
- Total length
- 32.94m
3 beams · 81 bars total
27 bars × 3 beams = 81 bars. 81 × 1220 / 1000 = 98.82m.
- Total length
- 98.82m
3. Convert total length into steel weight
Use the same 8mm bar and all three beams.
Unit weight · 0.4 kg per metre
Nominal unit weight = d² / 162. Keep the unrounded value in the calculation.
All stirrups · 39.04 kg
98.82m × the unrounded unit weight = 39.04kg. This excludes main bars and wastage.
The schedule you’re building toward
The same worked example throughout the course: three identical beams, with three bottom and three top main bars in each.
| Bar | Shape | Dia | Cutting length | Bars per member | Total bars | Total length | Weight | Notes |
|---|---|---|---|---|---|---|---|---|
| S1 | Stirrup · rectangular, 135° hooks | 8mm | 1220mm | 27 | 81 | 98.82m | 39.04kg | Uniform centres; no zones |
| B1 | Bottom main · straight | 16mm | 5500mm | 3 | 9 | 49.50m | 78.22kg | Straight anchorage at both ends |
| T1 | Top main · straight | 16mm | 5500mm | 3 | 9 | 49.50m | 78.22kg | Straight anchorage at both ends |
Total steel: 195.48kg. Worked quantities exclude wastage. Main bars assume straight anchorage fits each support; use the actual structural detail for a project.
A beam stirrup is one closed loop. What changes when a column needs cross-ties to restrain more bars?
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