General Information
Figure 1 shows a steel canopy roof.
![Steel canopy roof with hanger rods.](canopy-roofs/structure-6/1-canopy-roof.jpg)
Hanger Rods
Figure 2 shows the canopy roof.
![Steel canopy roof with hanger rods.](canopy-roofs/structure-6/2-canopy-roof.jpg)
The width b ≅ 3 m, and the length l ≅ 8 m. The canopy roof has four hanger rods with a square hollow cross section, which are placed in pairs and connected to the reinforced concrete structure of the building. Figure 3 shows a schematic partial three-dimensional view of the structure.
![Three dimensional drawing of a steel canopy roof with four hanger rods.](canopy-roofs/structure-6/3-3d-view.jpg)
The hanger rods are connected to the canopy roof as shown in figure 4.
![Connection between two hanger rods and canopy roof.](canopy-roofs/structure-6/4-hanger-rods-roof-connection.jpg)
Hanger rod 1 is connected to a purlin, which connects the transverse beams by short rectangular hollow profiles; hanger rod 2 is connected to the longitudinal front beam. The hanger rods are joined by welding.
What are some possible reasons for using four hanger rods?