What is the maximum un-braced length for purlins according to standard guidelines?

The maximum un-braced length for purlins is commonly determined by various building codes and engineering guidelines, which are designed to ensure structural integrity and safety. The correct option, indicating a maximum un-braced length of 8 feet for purlins, aligns with typical structural engineering practices that take into account factors such as the type of material used, the load applied to the purlins, and the intended use of the structure.

Purlins are horizontal members that support roofing and are essential in distributing the loads from the roof to the vertical structural elements. An un-braced length of 8 feet allows purlins to maintain sufficient stability and strength to resist lateral forces, bending, and buckling that may occur due to wind or other dynamic loads. This length ensures that purlins can effectively carry their designed loads while minimizing the risk of failure.

Choosing a longer un-braced length would increase the risk of structural deficiencies under load, as the purlins would have greater susceptibility to deflection and lateral-torsional buckling. Therefore, adhering to the 8-foot un-braced length guideline helps ensure the safety and durability of a roofing system.