Scaffolding may have two types of instability: global instability and local instability.
1. Overall instability
When the whole is unstable, the scaffold presents a horizontal frame composed of inner and outer vertical rods and horizontal rods. The large wave bulges along the direction of the vertical main structure. The wavelengths are all larger than the step distance and are related to the vertical spacing of the connecting wall pieces. Global buckling failure begins with transverse frames without wall attachments, with poor lateral stiffness or large initial bending. In general, overall instability is the main failure form of scaffolding.
2. Local instability
When local instability occurs, wavelet buckling occurs between the poles between the steps, the wavelength is similar to the step, and the deformation directions of the inner and outer poles may or may not be consistent. When the scaffolds are erected with equal steps and longitudinal distances, and the connecting wall parts are set evenly, under the action of uniform construction loads, the critical load of the local stability of the vertical poles is higher than the critical load of the overall stability, and the failure form of the scaffolding is the overall instability. When the scaffolds are erected with unequal step distances and longitudinal distances, or the setting of the connecting wall parts is uneven, or the load of the poles is uneven, both forms of instability failure are possible. The installation of the connecting wall is not only to prevent the scaffold from overturning under the action of wind load and other horizontal forces, but more importantly, it acts as an intermediate support for the vertical pole.
Post time: Sep-26-2022