purlin should be the priority to use solid belly members, can also use hollow type or lattice structure members. Purlins are generally single-span simply supported members, while purlins are also continuous members.
Purlin with full belly
1. Channel steel purlin
There are two kinds of ordinary channel purlin and light channel purlin. Ordinary channel steel purline (Figure a); Because the thickness of the profile is thicker, the strength cannot be fully developed, and the amount of steel used is larger. Light channel purlin is better than ordinary channel purlin, but it is still not ideal.
2.High-frequency welding light H-beam purlins
High-frequency welding light H-beam (hereinafter referred to as "light H-beam") is a kind of light beam produced by introducing foreign advanced technology (FIG. b), which has the advantages of thin web, good bending stiffness, relatively close moment of inertia of the two spindles, and easy connection of flange plate and so on.
3.Cold-formed thin-wall steel purlin with edge groove
The cold-formed thin-wall steel purlin with edge groove (Figure c) has a large cross section interchangeability and is widely used with less steel, which is easy to manufacture and install.
4.Edge-Zcold-formed thin-wall steel purlins
The Straight edge Z (Figure D) and the Oblique edge Z (figure E) are divided. Its main plane X-axis stiffness, used as small deflection when purlin, with steel saving, manufacturing and installation convenient. Oblique edge Z-shaped steel storage can be stacked, less floor space. When the roof slope is larger, this purlin is more common.
The connection structure of purlins
Purlin and roof should be connected reliably to ensure that roof can prevent lateral instability and torsion of purlin, which is especially important for solid belly purlin without checking overall stability.
Purlin and pressing steel plate roof connection, it is appropriate to use a rubber gasket with a self-tapping screw.
Brace and spporting bar: bolted to each other.
Purlin arrangement over roof truss (steel frame)
1. in order to make the roof truss upper chord does not produce a bending moment, purlin should be located in the roof truss upper chord node. When inner groove is used, edge purlin should be as close to the gutter as possible.
2. The section of purlin of solid belly should be perpendicular to the roof slope. For channel steel and Z-shaped steel purlin, it is advisable to turn the curling edge towards the roof ridge to reduce the torque caused by the eccentric roof load.
3. The upper chord of truss-type purlins should be perpendicular to the upper chord of roof truss, while the belly and lower chord should be perpendicular to the ground.
4. Ridge purlin scheme: Double purlin scheme shall be adopted for solid-belly purlin, and roof ridge purlin can be connected with channel steel, angle steel, or round steel (see figure below). When a single purlin scheme is used in truss purlin at roof ridge, although less steel is used, purlin models are increased and the structure is complex, so it is generally appropriate to use double purlin.