Classification Of Plane Truss Metal Purlins

Common plane truss purlins can be divided into two categories: one is made of angle steel and round steel; the other is made of cold-bent thin-walled steel.
1. Angle steel and round steel plane truss purlins
The upper chord of the purlin is placed in a V-shape with angle steel, as shown in Figure 3. This type of purlin has poor lateral stiffness, but it is easy to obtain materials and has clear force. It is suitable for roof loads or roofs with small purlin spacing. Due to the small purlin spacing, the purlin must be passed through when installing the upper chord support, which makes construction more troublesome. In order to solve this contradiction, the purlin with the upper chord support bay can be changed to a solid-web purlin.
2. Cold-bent thin-walled steel plane truss purlins
Cold-bent thin-walled steel plane truss purlins are divided into two categories.
(1) All the rods of the purlin are cold-bent thin-walled steel. It is suitable for roofs with large purlin spacing, uses less steel, has clear force, and has greater stiffness both inside and outside the plane.
(2) The main parts of the purlin, the upper chord and the end vertical compression rod, are made of cold-bent thin-walled steel, and the remaining rods are made of round steel, as shown in Figure 5. In order to enhance the stability of the purlin, its end compression web member is preferably made of square tube. It is mostly used for roofs with a purlin spacing of 1.5m. Compared with the previous flat truss purlin, this purlin has basically the same force performance, but is more convenient to obtain materials and manufacture.