Enter Truss Data
Example Data Table
| Input | Example Value | Meaning |
|---|---|---|
| Span | 10 m | Distance from support A to support B |
| Height | 3 m | Vertical rise to the apex joint |
| Apex Location | 5 m | Top joint centered between supports |
| Vertical Load | 80 kN | Downward joint load at the apex |
| Horizontal Load | 10 kN | Rightward joint load at the apex |
| Typical Result | AB tension, AC compression, BC compression | Member signs depend on the entered geometry and load |
Formula Used
The calculator uses static equilibrium for a simple triangular truss.
Horizontal balance: ΣFx = 0
Vertical balance: ΣFy = 0
Moment balance: ΣM = 0
Right support reaction: By = (P × apex + H × height) ÷ span
Left vertical reaction: Ay = P - By
Left horizontal reaction: Ax = -H
Member force method: each joint is solved with direction cosines.
Axial stress: stress = absolute axial force ÷ area
Euler buckling: Pcr = π²EI ÷ (KL)²
Positive member force means tension. Negative member force means compression.
How To Use This Calculator
- Select a unit system.
- Enter span, height, and apex location.
- Enter the vertical joint load.
- Enter horizontal load if wind or side force exists.
- Set a load factor for factored design checks.
- Add member areas for stress checks.
- Add modulus, K factor, and radius for buckling checks.
- Press calculate and review the result above the form.
- Use the CSV or PDF button to save the report.
Why This Truss Calculator Helps
A truss carries load through straight members. Each member mainly takes axial force. That force may pull, or it may push. Pulling force is tension. Pushing force is compression. This calculator models a simple three member truss. It uses a pin at the left support and a roller at the right support. The load is applied at the top joint. This layout is common in lessons, roof checks, bridge examples, and quick design reviews.
What The Tool Estimates
The tool first finds support reactions. It uses horizontal balance, vertical balance, and moment balance. Then it solves top joint equilibrium. The two sloped members are found from their direction cosines. The bottom chord is then solved from the left joint. The output labels each member as tension or compression. It also reports member length, axial stress, stress utilization, Euler buckling capacity, and buckling utilization when section data is entered.
Why Geometry Matters
Truss force changes when height, span, or apex position changes. A shallow truss often creates larger chord forces. A taller truss may reduce some axial demand. An off center apex changes reaction values. Horizontal load also changes reaction and member force. These effects are easy to miss by hand. The calculator shows them in one result table.
Use In Study And Early Checks
Use this page for learning and preliminary estimates. It is useful before drawing a full structural model. It can compare trial shapes and load cases quickly. It can also show how compression members may buckle before they reach material stress limits. That is why area, radius of gyration, effective length factor, and modulus are included. They give a stronger check than force alone.
Reading The Result
Positive member force means tension in this calculator. Negative member force means compression. Small rounding differences can appear. Keep enough digits when comparing manual calculations or class answers carefully.
Important Limits
Real structures may include many joints, eccentric connections, member self weight, load combinations, and local codes. This calculator assumes ideal pinned joints and axial member behavior. It also assumes all loads are applied at the top joint. Do not treat the result as final construction approval. A qualified engineer should review safety critical work.
FAQs
1. What does positive member force mean?
Positive member force means the member is in tension. It is being pulled along its length. Negative force means compression. It is being pushed along its length.
2. Can this calculator handle large roof trusses?
This version is for a simple three member triangular truss. Large roof trusses need a full joint model. Use this page for learning, quick checks, and simple triangular layouts.
3. Why is the apex location important?
The apex location controls member angle and reaction distribution. Moving it left or right changes the lever arm. It also changes the force split between the sloped members.
4. What is Euler buckling capacity?
Euler buckling capacity estimates the axial compression load that may cause a slender member to buckle. It depends on modulus, length, end condition, area, and radius of gyration.
5. Should I enter service loads or factored loads?
You can enter service loads and apply a load factor. You can also enter factored loads and set the factor to one. Keep your approach consistent.
6. Why does stress show N/A?
Stress shows N/A when the member area is missing or zero. Enter an area for each member. The calculator will then report axial stress and utilization.
7. Can horizontal wind load be entered?
Yes. Enter a positive value for rightward horizontal load. Enter a negative value for leftward load. The calculator includes it in reaction and member force equations.
8. Is this result suitable for final design?
No. It is a learning and preliminary checking tool. Final structural work needs code checks, connection design, load combinations, deflection checks, and review by a qualified engineer.