Model stay forces using vertical demand, cable angle, and quantity quickly today. See tension, components, stress checks, then download clean field files as needed.
Enter project demands and cable properties. The calculator estimates straight-cable tension and anchor components.
Sample inputs and typical outputs for quick checking.
| V (kN) | θ (deg) | Stays | L (m) | w (kN/m) | SF | T per stay (kN) |
|---|---|---|---|---|---|---|
| 1800 | 30 | 12 | 120 | 0.020 | 1.50 | ~ 389.7 |
| 950 | 25 | 10 | 95 | 0.015 | 1.35 | ~ 281.7 |
| 2400 | 35 | 16 | 140 | 0.023 | 1.50 | ~ 330.0 |
Values are illustrative. Your results depend on angle, distribution, and chosen factors.
Straight-cable equilibrium with an approximate self-weight term.
1) Self-weight contribution (approximate):
Vself = (w · L) / 2
2) Design vertical demand:
Vdesign = (V + Vself) · SF
3) Per-stay vertical share:
Vper = Vdesign / n
4) Cable tension and components:
T = Vper / sin(θ)
H = T · cos(θ)
V = T · sin(θ)
5) Stress and allowable check:
σ = (T · 1000) / A (MPa, with A in mm²)
σallow = fult / γm
Utilization (%) = (σ / σallow) · 100
This model assumes a straight cable line and distributes the vertical demand evenly across stays.
A practical workflow for fast estimation and reporting.
For detailed design, include sag, temperature, dynamic effects, and code-specific combinations.
A professional overview with a worked example for field-ready estimates.
Stay cables are primary load paths in cable‑stayed bridges and similar systems. Early checks often focus on the tension needed to deliver a required vertical component at a chosen angle. This calculator uses a straight‑line equilibrium model to estimate tension per stay, plus horizontal and vertical components at the anchorage. It also adds an approximate self‑weight contribution and applies a safety factor so preliminary sizing and coordination can move forward with consistent numbers.
Start by defining the vertical demand you want the stay system to support at the evaluated stage. This demand may represent dead load share, superimposed dead load, or a service combination used for quick checks. Next, set the cable angle to horizontal from your geometry. As the angle decreases, the required tension rises rapidly because the vertical component is T·sin(θ). For shallow stays, even modest vertical demands can produce high forces and large horizontal reactions into the deck and pylon.
The self‑weight term here is simplified: half the cable weight is assumed to contribute to the vertical demand at the anchor. In detailed analysis, cable sag and catenary effects alter both tension and component distribution, and construction stage effects can dominate. Use this tool to screen options, compare layouts, and create traceable calculations for discussions, not as a final design model.
Worked example: Suppose the total vertical demand is 1800 kN, the stay angle is 30°, and 12 stays share the demand. Let cable length be 120 m, self‑weight 0.020 kN/m, and safety factor 1.50. The approximate self‑weight contribution is (0.020·120)/2 = 1.2 kN. The design vertical demand becomes (1800 + 1.2)·1.50 ≈ 2701.8 kN, so each stay must provide about 225.15 kN vertically. The estimated tension per stay is 225.15/sin(30°) ≈ 450.3 kN, with a horizontal component of about 389.9 kN.
Finally, enter cable area and strength values to check utilization. Stress is computed from tension divided by area, and allowable stress is taken as ultimate strength divided by a material factor. Keep your project criteria consistent, document assumptions, and confirm governing combinations and detailing with the design team before procurement or field decisions.
For coordination, review pylon capacity, deck compression zones, and anchor detailing. If utilization exceeds 100%, increase area, raise angle, add stays, or reduce demand. Recalculate after adjustments to maintain margin.
Quick answers for typical design and coordination questions.
It is the angle between the cable and a horizontal line. The calculator uses it to split tension into vertical support and horizontal reaction at the anchor.
Vertical capacity is T·sin(θ). When θ is small, sin(θ) is small, so a larger tension is required to deliver the same vertical component.
The tool adds an approximate vertical term equal to half the cable weight, (w·L)/2, then applies the safety factor. Detailed models may redistribute weight differently.
Use it for preliminary checks, comparisons, and documentation. Final design should include sag, temperature, staged construction, dynamic effects, code load combinations, and detailed anchorage design.
Use kN for forces, meters for length, kN/m for self‑weight, and mm² for area. Strength is in MPa, which matches N/mm² used in the stress calculation.
Change the number of stays to reflect the effective load‑sharing group, or reduce the vertical demand to the portion carried by the specific stay set. Unequal distribution needs structural analysis.
Utilization compares computed stress to allowable stress. Values under 100% indicate capacity margin under the chosen factors; values above 100% suggest revising geometry, area, materials, or demand assumptions.
Verify assumptions with engineers before applying results onsite always.
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.