Cold-Formed Steel Purlins from China Suppliers - Reliable Factory Solutions for Roofing and Wall Cladding
Common Types of Cold-Formed Roof Purlins
C and Z sections are the most common shapes available for cold-formed steel purlins. As their names imply, these sections are bent according to the letter in the alphabet (refer to Figure 2). Z Purlins are point-symmetric, and sometimes their flanges are manufactured slightly unequally to allow overlapping. Meanwhile, C Purlins have a slightly lesser vertical section modulus, making them more advantageous for roofs with lower slopes. Each shape has its own pros and cons; it’s up to the engineer to assess the appropriate purlin based on the project requirements.
When installed on the roof, purlins are generally lapped with each other, providing continuity in the section. It is usually connected using machine-grade bolts through the webs of lapped purlins.
When it comes to its design, loads are applied on the normal and tangential axes of the section’s centroid. Thus, biaxial bending is mainly checked. Torsional effects on the member are assumed to be neglected due to the partial lateral and torsional restraints provided by the roof sheathing.
Advantages of Cold-formed Steel over Other Materials
This article focuses on the use of cold-formed steel (CFS). This type of steel is made from thin gauge sheets and, from the word itself, is made by cold working processes such as pressing and rolling, making it more durable as compared to hot-rolled sheets. In contrast with wood, cold-formed steel offers a longer lifespan as it is resistant to mold or vermin.
Since it is lightweight, CFS is easier to install and can even be recycled when the roofing system is removed or changed. When correctly constructed and designed, CFS structures can resist extreme environmental loads making it one of the most resilient materials available.
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Frequently Asked Questions
Z purlins are point-symmetric and often feature slightly unequal flanges to facilitate overlapping for section continuity. C purlins have a slightly lesser vertical section modulus, which makes them highly suitable and advantageous for roofs with lower slopes.
Purlins are typically lapped with one another to ensure structural continuity. They are securely connected using machine-grade bolts passing through the webs of the lapped purlin sections.
Torsional effects on the members are generally assumed to be negligible because of the partial lateral and torsional restraints provided by the roof sheathing attached to the purlins.
Cold-formed steel is manufactured from thin gauge sheets through cold working processes like pressing and rolling. This manufacturing method enhances its durability compared to hot-rolled sheets.
Cold-formed steel is highly lightweight, making it easy to install, and fully recyclable when the roofing system is replaced. Furthermore, unlike wood, it has a longer lifespan due to its resistance to mold and vermin.