Analyze spans using uniform, point, and lane loading. See reactions, bending, shear, and utilization instantly. Use results carefully for planning, study, and early reviews.
This bridge load calculator helps estimate preliminary reactions, shear, bending moment, bending stress, and deflection for a simply supported span. It combines dead load, live load, dynamic impact, and a concentrated point load in one practical workflow.
The tool is useful for concept design, classroom work, bid-stage checks, and early member comparison. It is not a substitute for full code-based analysis, vehicle load models, fatigue checks, influence lines, load combinations, bearing design, deck distribution analysis, or professional review.
You can enter a lane factor to amplify live load demand, then add a point load to simulate a wheel group, maintenance vehicle, equipment placement, or local concentrated action. The output section appears directly below the header after submission, making fast iteration easier.
Plotly charts visualize the internal force pattern across the full span. The shear graph helps locate abrupt changes caused by the point load. The bending moment graph helps identify peak flexural demand and compare it with available section resistance.
Adjusted live load: Live UDL × Lane Factor × (1 + Impact Factor / 100)
Total uniform load: Dead UDL + Adjusted Live UDL
Total load: (Total UDL × Span) + Point Load
Left reaction: (wL / 2) + P(L − a) / L
Right reaction: (wL / 2) + Pa / L
Shear at position x: V(x) = R₁ − wx − P when x is beyond the point load
Moment at position x: M(x) = R₁x − wx²/2 − P(x − a) when x is beyond the point load
Bending stress: σ = M / Z
Utilization: (Calculated Stress / Allowable Stress) × 100
Deflection: Calculated numerically from beam curvature using E and I inputs for the same loading case.
| Span (m) | Dead UDL (kN/m) | Live UDL (kN/m) | Point Load (kN) | Point Position (m) | Lane Factor | Impact (%) | Approx. Left Reaction (kN) |
|---|---|---|---|---|---|---|---|
| 20 | 16 | 12 | 90 | 8 | 1.10 | 10 | 322.26 |
| 30 | 22 | 18 | 160 | 12 | 1.20 | 15 | 675.60 |
| 36 | 25 | 20 | 210 | 15 | 1.25 | 20 | 915.42 |
It uses a simply supported beam model with combined uniform load and one point load. That makes it suitable for preliminary checks, teaching, and concept comparison, but not for final bridge design certification.
No. It does not automatically apply jurisdiction-specific bridge design codes, lane reduction tables, fatigue models, multiple presence factors, or detailed truck configurations. You must enter assumptions manually and verify them separately.
Impact factor lets you amplify live load effects to reflect dynamic action. It is applied to the live uniform load before combining with dead load, helping early-stage screening reflect more realistic demand.
Lane factor scales the live uniform load to represent traffic distribution or early design assumptions. It is useful when comparing scenarios, but it does not replace proper live load distribution methods.
The calculator divides the maximum bending moment by the entered section modulus. This produces an estimated flexural stress value, which is then compared with the allowable stress to show utilization.
Deflection results appear when both elastic modulus and moment of inertia are entered. The page then computes beam curvature numerically and reports midspan and maximum absolute deflection for the current load case.
No. Continuous spans, trusses, arches, cable-supported systems, staged construction, and composite action require different analysis methods. This page is built only for a single simply supported span approximation.
They are useful for quick study notes, option comparison, and internal review. They should be treated as preliminary summaries and checked against a full structural analysis workflow before formal submission.
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.