Plan strap layouts quickly for confined concrete repairs. Balance performance, cost, and installation effort safely. Generate spacing, quantity, and reports with one click now.
| Case | Wrap length (mm) | Strap width (mm) | Thickness (mm) | E (GPa) | Design strain | k_eff | phi | Demand (kN/m) | Min/Max spacing (mm) |
|---|---|---|---|---|---|---|---|---|---|
| A | 2000 | 50 | 1.2 | 230 | 0.006 | 0.85 | 0.90 | 120 | 50 / 300 |
| B | 1500 | 75 | 1.0 | 210 | 0.005 | 0.80 | 0.90 | 100 | 60 / 350 |
| C | 2500 | 40 | 1.4 | 240 | 0.007 | 0.90 | 0.85 | 140 | 50 / 250 |
The calculator treats each strap as a linear-elastic tension element at the chosen design strain. A reduced design tension is then distributed along the wrap length by the selected spacing.
Carbon straps provide confinement where cracking, corrosion, or seismic demand reduces capacity. Spacing converts a required confinement line load into a practical layout along the wrap length. The calculator treats each strap as a tension element at an effective design strain, then reduces that tension by efficiency and strength factors to reflect detailing and workmanship. For preliminary planning, demand may come from design calculations or specified strengthening targets. Use consistent units and confirm the wrap length represents the actual reinforced zone, not the full member span.
Spacing is driven by strap geometry, stiffness, and the confinement demand. Wider or thicker straps increase area, while a higher modulus and allowable design strain increase the usable tension. Efficiency accounts for curvature, anchorage, laps, and surface preparation. Strength reduction adds conservatism for material variability and field execution.
The adopted spacing is the demand-based value, limited by minimum and maximum bounds you set. The tool also distributes straps evenly between edge offsets, producing a practical spacing and quantity. Compare provided confinement to demand; an “OK” check indicates the distributed spacing meets or exceeds the required kN per meter. When demand is close to capacity, consider rounding spacing down to the next convenient increment for layout. The quantity output helps estimate material, adhesive, and installation time.
Use minimum spacing to prevent overlaps, wrinkling, and resin-rich zones, and maximum spacing to control crack widths and limit unconfined lengths. Confirm edge offsets avoid stress concentrations near terminations and allow access for rolling. If the calculated spacing is clipped by bounds, revisit demand assumptions, strap size, or allowable strain.
Exports summarize inputs, design tension, calculated spacing, distributed spacing, strap count, and the demand check. Attach the PDF to method statements, inspection records, and as-built packages. Keep the CSV for quick comparisons across members, enabling consistent layouts and clearer communication between designers, supervisors, and installers. Record batch numbers, surface moisture, and cure temperature with the report, and save files under clear member identifiers for future audits.
It is the design line load you want the straps to provide per meter of reinforced length. It can be derived from strengthening calculations, specifications, or retrofit targets, and should be consistent with your chosen design method.
They reduce ideal strap tension to a more realistic design value. Efficiency reflects detailing, curvature, anchorage, and workmanship effects. The strength factor adds conservatism for variability and site conditions.
The demand-based spacing may be clipped by your practical limits. If spacing is too tight or too wide, reconsider strap size, allowable strain, demand assumptions, or revise constructability limits to suit the project.
The tool subtracts edge offsets from the wrap length to get a usable length, then places straps at the adopted spacing and redistributes them evenly. This yields an integer strap count and a practical spacing.
Yes. Use it to compare scenarios and forecast strap count and layout. For final design, confirm material properties, effective strain limits, and detailing requirements with project specifications and governing standards.
Keep the exported report with member IDs, strap product data, surface preparation checks, adhesive batch numbers, ambient conditions, and cure temperatures. These details improve traceability and support quality assurance during reviews.
Important Note: All the Calculators listed in this site are for educational purpose only and we do not guarentee the accuracy of results. Please do consult with other sources as well.