1、 Roof truss

Structural form of roof truss: the structural form of roof truss mainly depends on the roof material used and the use requirements of the house.It is mainly composed of triangular roof truss, triangular arch roof truss, shuttle shaped roof truss and flat slope trapezoidal steel roof truss

There is no difference between light steel roof truss and ordinary steel roof truss in essence. The design principles of both are the same, but the section size of light steel roof truss is smaller, and the connection structure and service conditions are slightly different.

2、 Hinged support joint of trapezoidal roof truss

3、 Purlin

Form of purlin: solid web members should be preferred for purlins, and open web or lattice members can also be used.Purlins are generally single span simply supported members, and solid web purlins are also continuous members.

Open web purlin: the open web purlin is composed of the upper and lower chords of angle steel and batten plate welding. Its main feature is that the amount of steel used is less, and the small angle steel and thin steel plate can be reasonably used. Due to the close spacing between batten plates and the heavy workload of assembly and welding, it is less used.

Lattice purlin: plane truss purlin, space truss purlin and down bracing purlin can be used.

4、 Solid web purlin

1Channel steel purlin

It is divided into ordinary channel steel purlin and light channel steel purlin.Ordinary channel steel purlin (Fig. a); due to the thickness of the profile, the strength can not be fully utilized, and the steel consumption is large.Although the light channel steel purlin is better than the ordinary channel steel purlin, it is still not ideal.

2High frequency welding light H-beam purlin; high-frequency welding light-weight H-beam (hereinafter referred to as “light H-beam”) is a kind of light-weight steel produced by introducing foreign advanced technology (Fig.

3The cold-formed thin-walled steel purlin with lipped channel: the cross-section interchangeability of cold-formed thin-walled steel purlin (C-shaped) is large, and it is widely used, with less steel consumption and convenient manufacturing and installation.

4The cold-formed thin-walled steel purlin with crimping Z-shaped is divided into straight crimping Z-shaped (Fig. d) and obliquely crimped Z-shaped (Fig. E).Its main plane X-axis stiffness is large, when used as purlin, the deflection is small, the steel consumption is saved, and the manufacture and installation are convenient.The Z-shaped steel with inclined curling edge can also be stacked in layers with less land occupation.When the roof slope is large, this kind of purlin is widely used.

5、 Connection structure of purlin

The purlin and the roof should be reliably connected to ensure that the roof can prevent the lateral instability and torsion of purlin, which is particularly important for the solid web purlin without checking the overall stability.

The self tapping screw with rubber washer should be used for the connection between purlin and profiled steel sheet roof.

The brace and strut of purlin are connected with each other by bolts.

6、 Layout and shelving of purlin on roof truss (rigid frame)

1In order to avoid bending moment on the top chord of roof truss, purlin should be located at the node of roof truss upper chord.When the inner gutter is used, the side purlin should be as close as possible to the gutter.

2The cross section of solid web purlin should be perpendicular to the roof slope.For channel steel and Z-shaped steel bars, the upper flange limb tip (or curling edge) should be oriented towards the roof ridge to reduce the torque caused by eccentric roof load.

3The upper chord of truss purlin should be perpendicular to the top chord of roof truss, while the web and bottom chord should be perpendicular to the ground.

4Ridge purlin scheme: Double purlin scheme shall be adopted for solid web purlin, and ridge purlin can be connected with channel steel, angle steel or round steel (see the figure below).When the single purlin scheme is adopted at the ridge of truss purlin, although the steel consumption is less, but the purlin types are increased and the structure is complex, so the double purlin is generally suitable.