Flyover Span Length Calculator

Set length, limits, and preferred standard spans easily. Get balanced span layouts and quick checks. Export CSV or PDF to share with your team.

Inputs
Enter geometry and practical span constraints, then calculate.
Reset
All outputs follow this selection.
Along centerline between end reference points.
Seat, bearing, diaphragm, or detailing allowance.
Used when span count is auto-selected.
Too short can increase joints and bearings.
Capped further by selected superstructure type.
End span = factor × middle span (0.50–1.00).
If set, the solver fits spans to your count.
Range is used as a planning feasibility check.
If exceeded, suggests segments and expansion joints.
Affects displayed values and tables.

Example data table

Sample values show how inputs translate into a span schedule.
Scenario Total length (m) Support allowance (m) Preferred span (m) Min–Max (m) End factor Superstructure Output (typical)
Urban flyover 450 1.2 30 20–45 0.85 Prestressed I-Girder ~15 spans; end ~25.2, middle ~29.6
Longer mainline 900 1.5 55 35–70 0.90 Prestressed Box Girder ~17 spans; more uniform distribution
Short access ramp 160 1.0 18 10–20 0.95 RC Slab / T-beam ~9 spans; reduced bearing count

Formula used

The calculator splits total flyover length into supports and spans. Support allowances are deducted first, then the remaining length is distributed across spans.

Supports = Spans + 1
Support deduction = Supports × Support allowance
Span total = Total length − Support deduction

Let middle span = M, end span = E, end factor = k (E = k×M)
Span total = 2E + (n−2)M = 2kM + (n−2)M
M = Span total / ((n−2) + 2k)
E = k × M

If the span count is not provided, the calculator selects a count near your preferred span, then iteratively adjusts it to keep end and middle spans inside feasible limits.

How to use this calculator

  1. Choose units, then enter total flyover length.
  2. Set support allowance based on bearings and detailing needs.
  3. Enter span limits and a preferred standard span.
  4. Pick a superstructure type to apply planning span bounds.
  5. Optional: specify span count or max continuous length.
  6. Press Calculate and review the schedule, checks, and exports.

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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.