You may have encountered that sometimes a temporary steel structure building or stage can still be used after disassembly. Is there a limit on the number of reuse?

，要看看螺栓使用工况及螺栓本身类型，普通型螺栓连接一般情况没有明确禁止重复使用，但也需要做简单的检查，有无生锈是否严重，螺纹有没有变形，螺杆有没有缩颈现象，如果没有异常，就可以正常使用了。

First of all, we should look at the service conditions of bolts and the types of bolts. Generally, the reuse of ordinary bolt connection is not explicitly prohibited, but we also need to make a simple inspection to see whether there is serious rust, whether the thread is deformed, and whether the screw is necked. If there is no abnormality, it can be used normally.

对于高强度螺栓应用可以分为抗剪连接和抗拉连接，一般抗剪连接中螺栓仅承受初始预紧拉力，被连接件在初始预紧拉力的作用下接触面之间有很高的压力，在外力作用时可产生可观的摩擦力。

The application of high-strength bolts can be divided into shear connection and tensile connection. Generally, in shear connection, the bolts only bear the initial pre tightening tension, and there is a high pressure between the contact surfaces of the connected parts under the action of the initial pre tightening tension, which can produce considerable friction under the action of external force.

高强度螺栓用于抗拉型连接时，一般螺栓除了承受初始预紧力之外，还要承受外部工作载荷或者动态疲劳载荷。

When high-strength bolts are used for tensile connection, the general bolts not only bear the initial preload, but also bear the external working load or dynamic fatigue load.

为了保证比较高的疲劳强度和高承载能力，高强度螺栓一般都要施加一个很大的预紧力，一般这种预紧力扭矩法来拧紧实现的。

In order to ensure relatively high fatigue strength and high bearing capacity, high-strength bolts generally have to apply a large preload, which is generally realized by tightening with this preload torque method.

扭矩法拧紧都需要施加很大的扭矩，且预拉力的精  确度高度依赖摩擦系数的稳定性，高强度螺栓联接副一般都要求同批次使用，不得混批使用，及螺栓螺母垫圈都是配好的，不能随意螺栓螺母搭配使用。

Torque tightening requires great torque, and the accuracy of pretension highly depends on the stability of friction coefficient. High strength bolt connection pairs are generally required to be used in the same batch, and shall not be used in mixed batches. Bolts, nuts and washers are well matched, and bolts and nuts cannot be used at will.

由于一次使用过程中拧紧扭矩很大，螺纹副上螺纹牙型和螺母接触面都经历了高强度摩擦，是螺纹接触面和螺母接触面表面粗糙度都发生了很大的变化，因此摩擦系数也产生了很大的变化，再用同样的扭矩拧紧时，可能产生更大的拉伸力可能把螺栓拉断。

Due to the large tightening torque during one use, the thread profile on the thread pair and the nut contact surface have experienced high-strength friction. The surface roughness of the thread contact surface and the nut contact surface has changed greatly, so the friction coefficient has also changed greatly. When tightening with the same torque, greater tensile force may be generated and the bolt may be broken.

使用时间比较久的高强度螺栓有螺纹连接处锈蚀的可能，因此在拆卸的过程中可能需要比较大的扭矩才能松开螺母，大扭矩可能把螺栓扭断或者严重的扭剪变形，再次使用时风险很高，高强度螺栓一般都用在比较重要的连接位置，因此应避免风险。

The high-strength bolts that have been used for a long time may have the possibility of corrosion at the threaded connection. Therefore, a large torque may be required to loosen the nut in the process of disassembly. A large torque may break the bolt or cause serious torsional shear deformation. The risk is very high when they are used again. High-strength bolts are generally used at important connection positions, so the risk should be avoided.

因此高强度螺栓不能重复使用，但也有例外，比如，如果螺栓的预拉力是靠直接拉伸实现的，这种情况重复使用就影响不大，前提是松螺母时松卸扭矩不能大于拧紧扭矩或超出很小。

Therefore, high-strength bolts cannot be reused, but there are exceptions. For example, if the pretension of bolts is realized by direct tension, the reuse will have little impact, provided that the loosening torque cannot be greater than the tightening torque or exceed very little when loosening the nut.