How to get the correct maximum rail span values when using SunModo SMR racking systems
ASCE 7-16
Good news! Lyra utilizes an API to automatically get rail spans for projects using SunModo mounting. Rail span values should automatically populate on the Mounting BOS step.
Manual lookup
When specifying the Mounting BOS for a design using a SunModo SMR racking system, one important data point to consider is the maximum rail span for roof zones 1, 2, and 3.
Why are these numbers important?
Correct values for these fields are critical. Everything from accurate maximum cantilever values (and thus accurate attachment layouts) to accurate calculations of racking hardware weights and quantities of racking hardware components on the bill of materials are affected by these numbers. If you use erroneous values to rush through the design process, some parts of your permit package (such as the attachment layout and racking hardware quantities and weights) may be inaccurate or missing.
How do I find the maximum rail spans for my design?
Find the correct maximum rail span values using the span tables provided by SunModo.
- Get the ground snow load and wind speed rating, if they weren't added automatically, for your address here. This is added to your project in the Environmental Parameters section. Read more about that here.
- Look up the maximum rail spans for each wind zone for the Crossrail product you will be using by downloading the span tables for your state here
Alternatively, design your project with SunModo's configurator software to find the maximum rail spans.
Note: Maximum rail span, which is based on the mechanical properties of the rail, differs from maximum attachment spacing, which is based on the roof's structural limitations. Wider attachment spacing results in greater point loads on the roof at each attachment point. Optimal attachment spacing depends on many factors, such as the roof structure, roof condition, snow loads, wind loads, etc.