Estimate mullion strength and stiffness for wall design. Choose units, span type, and properties confidently. Get clear results and practical next steps today, now.
| Case | Pressure | Spacing | Span | Span type | Deflection | Typical use |
|---|---|---|---|---|---|---|
| A | 1.2 kPa | 1.5 m | 3.0 m | Single | L/175 | Mid-rise elevations |
| B | 1.8 kPa | 1.5 m | 3.6 m | Two-span | L/240 | Long mullions with intermediate support |
| C | 2.4 kPa | 1.2 m | 4.2 m | Single | L/175 | Corner zones or higher exposure |
Curtain wall mullions convert façade pressure into a line load using w = p × b, where p is design wind pressure and b is tributary width or spacing. For example, 1.8 kPa on 1.5 m spacing produces 2.7 kN/m line load before any project safety factor. Spacing often follows glass module and can range from 1.2 m to 1.8 m on many stick systems. Check local exposure. Use corner and edge zone pressures when they govern, not the building average.
Support conditions change the governing moment and deflection. A single simply supported span uses M = wL²/8 with deflection δ = 5wL⁴/(384EI). Two equal continuous spans reduce positive midspan moment but introduce a negative interior-support moment. The calculator reports both positive and negative moments so you can size for the larger demand. For unequal spans, use a frame analysis.
Deflection limits are typically expressed as L/175, L/240, or more stringent project criteria for vision glass, sealants, and movement joints. If glass-edge rotation or bite is sensitive, stiffness may control the selection even when stresses are low. Always confirm the supplier’s allowable deflection guidance for the glazing type and framing system.
The modulus of elasticity E drives stiffness while allowable stress governs strength sizing through Sreq = M/σ. Typical aluminum uses E ≈ 69 GPa (about 10,000 ksi), but allowable stresses vary by alloy, temper, and design method. Compare the required S and I against published section tables for your intended mullion profile. If negative moment governs, confirm capacity in both bending directions.
Exported CSV and PDF outputs support quick concept reports and option studies. After a profile is selected, validate anchors, splice details, dead load transfer, thermal movement, and differential drift. If mullion spacing changes, re-run the tributary width because line load scales directly with spacing. Treat the estimated depth as a guide only; real extrusions can be much more efficient than a solid rectangle. For traceability, record the wind source, zone, and date used in the notes field.
It provides target section properties: required section modulus (S) for bending stress and required second moment of area (I) for deflection control under uniform wind loading.
Use single span when the member is supported only at its ends. Use two-span when an intermediate support creates two equal spans and continuity, which introduces a negative support moment.
Either can be used. If you enter factored pressure from your code workflow, keep the safety factor at 1.0. If you enter nominal pressure, apply an appropriate safety factor for conservative targets.
Continuous members develop sagging moment in spans and hogging moment over supports. Some sections govern at the interior support due to negative moment, especially with stiff connections.
L/175 is common for many systems, while L/240 or tighter may be specified for large glazing, higher performance façades, or where sealant and glass edge behavior is critical.
No. Use it for concept sizing and option screening. Final design should include detailed load combinations, connection behavior, drift and movement, supplier limits, and engineer-of-record verification.
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.