Model bridge panels, materials, and loading conditions. Review reactions, member forces, and vertical deflection instantly. Download neat reports for planning, checking, and project documentation.
| Example input | Value |
|---|---|
| Span | 30 m |
| Panels | 6 |
| Truss height | 6 m |
| Dead load | 20 kN/m |
| Live load | 35 kN/m |
| Elastic modulus | 200 GPa |
| Top chord area | 6000 mm² |
| Bottom chord area | 6000 mm² |
| Vertical area | 4500 mm² |
| Diagonal area | 5000 mm² |
| Extra loads | 2:120,3:120,4:120 |
| Example output | Value |
|---|---|
| Left vertical reaction | 1,005.000 kN |
| Right vertical reaction | 1,005.000 kN |
| Maximum tension member | BC3 (1,381.250 kN) |
| Maximum compression member | TC4 (-1,216.667 kN) |
| Maximum vertical deflection | B3 (-63.509 mm) |
Panel load conversion: interior top joint load = w × panel length. End top joint load = 0.5 × w × panel length. Extra loads are added directly to selected top joints.
Global stiffness method: each member uses the standard two dimensional truss stiffness matrix. The calculator assembles all member matrices into one global matrix and solves Kf × uf = Ff for unknown joint displacements.
Member axial force: N = (A × E / L) × [ -c -s c s ] × u.
Member stress: stress = N / A.
Support reactions: R = K × u - F.
Equilibrium check: sum of vertical reactions should match total vertical loading, subject to small numerical rounding.
A truss bridge analysis calculator helps engineers study force flow before detailing members. It estimates reactions, axial forces, stresses, and joint deflection in one place. That saves checking time. It also improves design clarity during concept work, teaching, and feasibility reviews.
This tool models a two dimensional bridge truss with top chords, bottom chords, verticals, and diagonals. You enter span, panel count, truss height, material stiffness, and member areas. You can also apply dead load, live load, and extra joint loads. The solver converts deck loading into nodal forces and builds a stiffness matrix for the structure.
The output highlights support reactions, maximum tension, maximum compression, and peak vertical deflection. It also lists each member force and stress. Those values help you size members, compare load cases, and identify critical bars. A good preliminary model can reveal inefficient geometry, before drawings become expensive to revise.
Bridge teams can use this calculator for classroom exercises, proposal studies, and verification. Contractors can compare service loads better. Students can observe how panel count and truss height change internal actions. Reviewers can inspect whether compression members or slender diagonals deserve closer attention under heavier loading.
Longer spans usually increase axial demand and deflection. Greater truss depth usually reduces chord force and improves stiffness. More panels can distribute loading more smoothly, though they also add members and connections. Balanced proportions often improve economy. This is why geometry testing is valuable when comparing bridge options.
Positive axial force indicates tension. Negative axial force indicates compression. Stress values combine force and member area, so they help compare different bar groups. If a member shows large compression in real practice, it may need a buckling review beyond this simplified calculation model.
This calculator is intended for preliminary analysis only. Real bridge design also requires code checks, connection design, buckling review, fatigue review, load combinations, and modelling. Always confirm final values with project criteria, governing standards, and a full engineering workflow before construction decisions are made.
It models a determinate parallel chord truss with chords, verticals, and diagonals. The layout is suitable for preliminary bridge style studies and teaching examples.
No. Use it for preliminary analysis, screening, and learning. Final design still needs governing codes, buckling checks, connection design, fatigue review, and detailed modelling.
The calculator converts the entered kN/m loading into equivalent top joint loads. Interior joints take full panel load. End joints take half panel load.
Positive axial force means tension. Negative axial force means compression. The state column labels each member clearly for quick engineering review.
Deeper trusses often reduce chord force and improve stiffness. A shallow truss may carry the same load, but usually with larger force demand and deflection.
Yes. Enter extra top joint loads as joint:load pairs, separated by commas. Example: 2:120,3:80 applies downward loads at joints T2 and T3.
Use metres for geometry, kN/m for distributed loads, kN for extra joint loads, GPa for elastic modulus, and mm² for member areas.
It confirms that vertical reactions closely match total applied vertical loading. Small residual values come from numerical rounding during matrix calculations.
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.