Steel structure-layout of roof purlin

1. Roof truss

The structure of the roof truss: The structure of the roof truss mainly depends on the roofing materials used and the requirements of the house. Mainly triangular roof truss, triangular arch roof truss, shuttle roof truss, flat slope trapezoidal steel roof truss.

There is not much difference in essence between light steel roof truss and ordinary steel roof truss. The design methods of the two are the same, except that the cross-section size of the members of the light steel roof truss is smaller, and the connection structure and use conditions are slightly different.

2. Purlin

The form of the purlin: the purlin should preferably adopt solid web members, but also can use empty web or lattice members. Purlins are generally single-span simply supported members, and solid web purlins can also be continuous members.

Open-web purlin: The open-web purlin is composed of the upper and lower chords of the angle steel and the welding of the plaque. Its main feature is that the amount of steel is small, and the small angle steel and thin steel can be reasonably used. The workload is larger, so there are fewer applications.

Lattice type purlin: The lattice type purlin can adopt plane truss type, space truss type and under support type purlin.

3. Connection structure of purlin

The purlin and the roof should be reliably connected to ensure that the roof can prevent lateral instability and torsion of the purlin. This is particularly important for solid-belly purlins that generally do not need to check the overall stability.

The connection between the purlin and the profiled steel plate roof should adopt self-tapping screws with rubber washers.

The brace and brace of the purlin: bolted to each other.

4. The arrangement and shelving of the purlin on the roof truss (rigid frame)

•  In order to prevent bending moment on the upper chord of the roof truss, the purlin should be located at the upper chord node of the roof truss. When using the inner gutter, the side purlin should be as close as possible to the gutter.

• The cross-sections of solid web purlins should be perpendicular to the roof slope. For channel steel and Z-shaped steel sandalwood strips, it is advisable to point the top flange tip (or curling) towards the roof ridge to reduce the torque caused by roof load eccentricity.

• The upper chord of the truss purlin should be perpendicular to the upper chord of the roof truss, while the web and lower chord should be perpendicular to the ground.

• Ridge purlin plan: The solid web type purlin should adopt the double purlin plan, and the roof ridge purlin can be connected with channel steel, angle steel or round steel (see the figure below). When the truss-type purlin adopts a single purlin scheme at the ridge, although the amount of steel used is less, the number of purlins is increased and the structure is complicated, so it is generally appropriate to use double purlins.