Scaffold fasteners are composed of pads, bases, brackets, horizontal rods, scissors support, throwing, soft wall rods, scaffolding, etc. Each scaffold fastener plays an important role in the load-bearing capacity of the lathe.
1、 Scissor support
The main function of scissors support is to increase the stiffness of the scaffold and maintain the integrity of the scaffold structure. During normal use, the scaffolding has low strength and its main function is to support the support during unstable moments of the lathe.
There are two types of scissors support. Vertical scissors support can mainly improve the stability of the frame and effectively reduce the vertical displacement of nodes inside the frame. Transverse shear support mainly limits the horizontal displacement of the frame to ensure the stiffness of the frame in the plane direction.
The experiment shows that as the shear support increases, the number of diagonal frames in the scaffold represents the number of shear supports in the entire frame. The proportion of diagonal frames in the entire frame is about 5%, and the shelf load force accounts for about 30%, 15-20%, and the lathe load force increases by about 1.5 times, showing a tilted state. The relevant specifications for scaffolding also indicate that the critical load of the lathe is increased by about 26% -64% compared to the one without scissors support.
When the bracket collapses, the changes in the bracket of the scissor bracket are consistent with the collapse and failure state of the bracket. Therefore, the scissor bracket is the last pillar before the bracket collapses. Reasonable setting of the scissor bracket is particularly important to prevent the bracket from collapsing.
2、 Horizontal rod
The damage of scaffolding fasteners is mainly caused by the horizontal force of the lathe. The lathe undergoes slight disturbance during external forces or icing, leading to deviation in the verticality of the lathe. When the upper part of the lathe bears a greater load, a chain reaction occurs, resulting in a huge horizontal force between the lathes, thereby damaging the lathe.
At the moment before the lathe is destroyed, due to the small horizontal displacement, the force model can be simplified as a static fixed continuous beam hinge structure, and the horizontal rod part can be considered as hinge.
When the support is subjected to horizontal forces, the maximum bending moment and maximum reaction force of the support will be displayed in the first node section at the top. That is to say, when the bracket is subjected to a horizontal force, the force on the first horizontal rod at the top is the greatest. In addition, the magnitude of the force is proportional to the length of the vertical lever extending to the top elevation rod (i.e. the value A in the figure). In practical engineering, when the vertical lever extends the top elevation rod length by 0.5 meters, the support force increases by 13.43% compared to when the vertical lever extends the top elevation rod length by 0.8 meters.
Because components are slender, Euler's formula can be used to calculate forces. That is to say, its value is determined based on the endpoint conditions of the component. Reasonable setting of the broom can effectively improve the stress conditions at both ends of the component and reduce the value. Therefore, the force of the scaffold is not only greatly affected by the top horizontal rod, but also by the force of the bottom broom on the frame body.
When the broom is not set, the physical energy model of the lathe is similar to the hinge at both ends, with a value of 1. When a horizontal rod is set at the bottom of the lathe, the force model is similar to the fixed floor and the upper hinge, with a value of 0.7. From the Euler formula, it can be seen that the difference in the limit values of the two loading forces is about twice.
From this, it can be seen that the setting of the first horizontal bar at the top of the scaffold fastener and the setting of the sweeping floor have a significant impact on the bearing capacity of the frame, so special attention should be paid.
3、 Scaffold fasteners
In practical engineering, most frame collapses do not occur when the steel pipe exceeds the load. If the car