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?

，要看看螺栓使用工況及螺栓本身類型，普通型螺栓連接一般情況沒有明確禁止重復使用，但也需要做簡單的檢查，有無生銹是否嚴重，螺紋有沒有變形，螺桿有沒有縮頸現(xiàn)象，如果沒有異常，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.

對于高強度螺栓應用可以分為抗剪連接和抗拉連接，一般抗剪連接中螺栓僅承受初始預緊拉力，被連接件在初始預緊拉力的作用下接觸面之間有很高的壓力，在外力作用時可產(chǎn)生可觀的摩擦力。

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.

高強度螺栓用于抗拉型連接時，一般螺栓除了承受初始預緊力之外，還要承受外部工作載荷或者動態(tài)疲勞載荷。

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.

為了保證比較高的疲勞強度和高承載能力，高強度螺栓一般都要施加一個很大的預緊力，一般這種預緊力扭矩法來擰緊實現(xiàn)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.

扭矩法擰緊都需要施加很大的扭矩，且預拉力的精  確度高度依賴摩擦系數(shù)的穩(wěn)定性，高強度螺栓聯(lián)接副一般都要求同批次使用，不得混批使用，及螺栓螺母墊圈都是配好的，不能隨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.

由于一次使用過程中擰緊扭矩很大，螺紋副上螺紋牙型和螺母接觸面都經(jīng)歷了高強度摩擦，是螺紋接觸面和螺母接觸面表面粗糙度都發(fā)生了很大的變化，因此摩擦系數(shù)也產(chǎn)生了很大的變化，再用同樣的扭矩擰緊時，可能產(chǎn)生更大的拉伸力可能把螺栓拉斷。

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.

使用時間比較久的高強度螺栓有螺紋連接處銹蝕的可能，因此在拆卸的過程中可能需要比較大的扭矩才能松開螺母，大扭矩可能把螺栓扭斷或者嚴重的扭剪變形，再次使用時風險很高，高強度螺栓一般都用在比較重要的連接位置，因此應避免風險。

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.

因此高強度螺栓不能重復使用，但也有例外，比如，如果螺栓的預拉力是靠直接拉伸實現(xiàn)的，這種情況重復使用就影響不大，前提是松螺母時松卸扭矩不能大于擰緊扭矩或超出很小。

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.