Views: 0 Author: Site Editor Publish Time: 2026-01-02 Origin: Site
Picking the wrong PC strand size can wreck your whole project. Too small and it won't carry the load. Too big and you're wasting money.
So how do you choose the right diameter? What load capacity do you actually need? Let's make sense of prestressing strand sizing once and for all.
PC strand size isn't random. The industry settled on specific diameters that work for most prestressed concrete applications.
Here's what you'll find at Tj Wasungen and other suppliers:
Common Sizes:
9.5mm (3/8 inch): Small precast products
12.7mm (1/2 inch): Most popular, workhorse size
15.2mm (0.6 inch): Heavy bridge girders
15.7mm (0.62 inch): Major infrastructure
The 12.7mm diameter dominates the market. You'll see it everywhere from parking garages to bridge decks. Why? It hits the sweet spot between capacity and handling.
Here's something that trips people up. The PC strand size you order isn't exactly the diameter you measure.
When you order 12.7mm strand, that's the nominal size. Measure with calipers and you might get 12.4mm or 12.9mm. That's normal. ASTM A416 allows tolerances.
Why does this matter? When calculating how many strands fit in a duct, use actual measurements, not nominal.
The whole point of choosing different PC strand size options is matching capacity to your needs:
9.5mm (3/8 inch)
Breaking strength: 102 kN (23,000 lbs)
Best for: Railroad ties, hollow-core slabs
12.7mm (1/2 inch)
Breaking strength: 186 kN (41,800 lbs)
Best for: Bridge decks, parking structures, building floors
15.2mm (0.6 inch)
Breaking strength: 265 kN (60,000 lbs)
Best for: Long-span girders, heavy infrastructure
15.7mm (0.62 inch)
Breaking strength: 287 kN (64,500 lbs)
Best for: Stadium roofs, nuclear containment
Tj Wasungen stocks these sizes ready to ship. Need something special? We can manufacture custom diameters, but standard sizes save you time and money.
You can't just guess at PC strand size. Math keeps bridges standing. Here's the process:
Step 1: Your engineer calculates total prestressing force needed (based on span, loads, design).
Step 2: Choose working stress at 70-80% of ultimate strength. For 12.7mm strand with 186 kN capacity, use about 130-148 kN per strand.
Step 3: Divide total force by force per strand. Example: 2,000 kN ÷ 140 kN = 14.3, round up to 15 strands.
Step 4: Verify they fit in your duct or beam cross-section.
Should you use a few big strands or many smaller ones?
Larger Diameters:
Simpler installation, less threading
Fewer anchorages to set
Better reserve capacity if one fails
Crew works faster
Smaller Diameters:
More flexible placement
Distribute force evenly
Bend to tighter radii
Sometimes cheaper material cost
Factor in installation labor before deciding.
The PC strand size you pick changes how your crew works:
Minimum Bend Radius:
9.5mm: 300mm radius minimum
12.7mm: 400mm radius minimum
15.2mm: 500mm radius minimum
15.7mm: 550mm radius minimum
Exceed these and you risk damaging the prestressing steel.
Anchorage Compatibility: Your chosen PC strand size must match available anchorages. Standard sizes have lots of options. Custom sizes? You're stuck with limited choices.
Check anchorage availability before finalizing your strand order.
Threading Difficulty: Smaller strand threads through ducts easier. But you're threading more of them. Larger strand might bind in tight duct bends.
Your PC strand size dictates what ducts you need for post-tensioning work:
Single Strand:
9.5mm: 35-40mm duct
12.7mm: 50-60mm duct
15.2mm: 70-80mm duct
Multiple Strands (12.7mm):
4 strands: 75mm duct
7 strands: 100mm duct
12 strands: 125mm duct
19 strands: 150mm duct
Tj Wasungen can help you calculate exact duct requirements.
Does PC strand size affect what you pay? Absolutely.
Price Per Ton:
9.5mm: Base price
12.7mm: Base + 2-3%
15.2mm: Base + 5-8%
15.7mm: Base + 8-12%
But don't just look at material cost. Larger strand means fewer pieces to handle, less installation labor, and fewer anchorages to buy.
Run the complete cost calculation before choosing based on strand price alone.
PC strand size affects manufacturing difficulty:
Thinner strand shows more variation in properties. The wire drawing process is less forgiving on small diameters. Quality manufacturers like Tj Wasungen maintain tight tolerances regardless of size.
All sizes get tested: breaking strength tests, elongation verification, and relaxation testing apply to every diameter.
Confusing Nominal with Actual: Designing ducts based on nominal diameter? You might come up short. Always verify actual measurements.
Ignoring Anchorage Availability: Choosing 15.7mm strand when only 15.2mm anchorages are available? Now you're stuck.
Not Planning for Tolerances: ASTM A416 allows diameter variations. Your design needs to accommodate the tolerance range.
Assuming All Strands Are Equal: A 12.7mm strand from one manufacturer might have different properties than another's. Check the actual breaking strength and metallic area.
Ready to buy? Here's how to get exactly what you need:
Specify Completely:
Diameter (metric or imperial)
Grade (1860 MPa standard)
Coating (bright, galvanized, epoxy)
Relaxation class (low relaxation)
Quantity needed
Delivery timeline
Request Documentation: Every coil should come with mill test reports. Tj Wasungen provides complete test reports automatically.
Verify Stock: Call suppliers near you to confirm they've got your chosen PC strand size in stock. Don't assume.
Plan for Extras: Order 5-10% more than calculated. Installation waste happens. Better to have extra than run short mid-project.
We help contractors and engineers pick the right PC strand size every day:
Free Engineering Consultation: Not sure which diameter fits your application? Our technical team reviews your requirements and recommends the optimal size.
Stock Inventory: We keep 9.5mm, 12.7mm, and 15.2mm strand in stock. Most orders ship within 48 hours.
Complete Documentation: Every shipment includes mill test reports, material certifications, and handling instructions.
Choosing the right PC strand size isn't complicated once you understand the basics. Match diameter to your load capacity requirements. Consider installation factors. Verify anchorage compatibility.
The 12.7mm diameter handles most prestressed concrete work beautifully. Go smaller for precast products. Go larger for heavy infrastructure.
Need help selecting PC strand size for your next project? Tj Wasungen is ready to answer questions and provide exactly what you need.
