KEVOS® MAKEOS · Strength
Two-Span Stringer Check (Continuous Beam, Deflection, Support Reactions)
Is a beam running continuously over three supports strong and stiff enough for this load, and can the middle support take its share?
Check of a stringer, rail or pipe-rack beam continuous over two spans with a uniform load plus its own weight: support reactions, the negative moment over the middle support, the span moments, the bending stress and the span deflections (as the continuous beam over two spans tool), against your allowable stress, deflection limit as a fraction of span, and the capacity of each support.
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How this tool works
Inputs, units and where to find them
| Input | Unit | Typical source |
|---|---|---|
| Span 1 | mm | Length of the first span. |
| Span 2 | mm | Length of the second span. |
| Applied uniform load | N/m | Uniform load on the beam (both spans). |
| Beam mass per metre | kg/m | Mass of the beam per metre (added to the load). |
| Elastic modulus | GPa | Elastic modulus. |
| Second moment of area | mm⁴ | Second moment of area of the beam about its bending axis. |
| Distance to extreme fibre | mm | Distance from the neutral axis to the extreme fibre. |
| Allowable bending stress | MPa | Allowable bending stress. |
| Deflection limit (span ÷ …) | Deflection limit as span divided by this number. | |
| Capacity of each support | kN | Load each support, bracket or column can take. |
Method and formulas
- Total load per metre = applied + mass × g on both spans.
- Middle-support moment from the three-moment equation; reactions, span moments and deflections by superposition (as the continuous beam over two spans tool).
- Stress = largest moment × c ÷ I; deflection limit = span ÷ ratio.
- Example: the middle support carries 8.0516 kN; the beam is stressed to 15.097 MPa and deflects 0.58871 mm.
Limitations
- Prismatic beam on rigid supports at the same level; support settlement changes the moments.
- Uniform load on both spans; patterned live loads can raise span moments.
- Example values are illustrations. Replace them with values for your actual task.
Typical uses
- Check a conveyor stringer or rail over three supports
- Size a pipe-rack beam
- Find the load on a middle support
Who it is for
- Structural designers
- Design engineers
- Fabrication engineers
What you get
- Support reactions
- Moments and bending stress
- Span deflections against the limit
Interpreting the result
- The middle support of equal spans takes about 1¼ times the load of one span: check it first.
References
- Machinery’s Handbook, 29th edition (Industrial Press, 2012), printed pp. 264–267. Topic reference; no source tables or recommended settings are reproduced.
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Open the Two-Span Stringer Check (Continuous Beam, Deflection, Support Reactions) calculator
