The angle of Z-shaped purlin is different from that of C-shaped purlin. C-shaped purlin is 90 degrees, and Z-shaped purlin is less than 90 degrees, about 60 to 75 degrees. Therefore, when using purlins for roofs with a certain slope, the angle of purlins should be considered in combination with the stress knowledge. Adopting Z-shaped purlins for large slopes can make full use of its bending resistance.
Compared with the Z-section, the mechanical properties of the strong and weak axes of the C-section are greatly different, and the connection with the rigid frame is mostly bolt hinge, which must be considered as simple support (the rigid connection between the z-sections can be realized by reliable lapping, so it can be calculated as a continuous beam). Therefore, the latter is more reasonable from the perspective of stress state, calculation results and structure. Therefore, in addition to the processing needs of door and window openings and other special nodes, the Z-shaped section shall be preferentially selected. Wall purlins and roof purlins with small slope can be C-shaped; The roof purlin with large slope should be Z-shaped, and it is better to make the resultant force of roof load pass through the section centroid of Z-shaped purlin.
1) When the roof slope is small, the bending section modulus of Z-type purlin is slightly larger than that of C-type purlin, but the difference is not significant; When the roof slope increases, the utilization ratio of the bending section modulus of the Z-shaped purlin symmetrical to the vertical direction increases. Therefore, Z-shaped purlins are suitable for roofs with large slopes;
2) For the wall, there is no big difference in choosing Z-type or C-type;
3) If the purlin is to be made into a continuous member, the best is Z-shaped purlin, because it is easy to overlap.