Rolled straight thread connection technology for steel bars in building construction

Based on the actual situation of the development of the current social construction industry, it is not difficult to find that in recent years, the steel rolling straight thread connection technology has been gradually promoted and applied in China’s urban and rural construction projects because of its own economical and reasonable and reliable quality characteristics. Through the observation of the actual situation of construction, it is found that the technology plays an important role in ensuring the quality of engineering construction, so it is necessary to conduct feasibility studies on the technology to promote the effective implementation of construction.

1 The advantages of rolling straight thread connection technology for reinforcing bars

In the actual construction process, the rolled straight-threaded connection technology is based on its simplicity and reliable quality, and the actual stable operation of all aspects of the connection facilitates the realization of the purpose of the connection. In terms of construction specifics, the rolled straight thread connection technology has the following advantages.

It is relatively easy to operate during the construction process, and the technology is non-polluting, non-open flame, and relatively safe to operate. The strength of the joint is high and the tightening force does not affect the performance of the joint too much, and the quality of the rebar threads meets the national standards and the processing accuracy is high, which makes the quality of the rebar connection reliable. From these two aspects, the technology does not easily affect the construction quality, and to a certain extent promotes the improvement of the construction quality to meet the relevant standards.

The reliable connection quality of this technology and the relatively good fatigue resistance of the joints in the actual application process make it widely applicable to reinforced concrete construction structures under various environmental conditions, which are usually not affected by the construction environment and climatic conditions, and the construction site environment is relatively neat and clean, with relatively little noise pollution and smoke pollution, thus helping to protect the health of construction personnel.

The construction quality of the straight threaded rolling connection technology is easy to control, and is not easily affected by human factors and the external environment. Usually, the exposed wire buckle is within two turns to reduce the safety risks.

2 The practical application of rolling straight thread connection technology for steel bars

  2.1 Construction process

The upsetting straight thread process is to first use the cold heading machine to upset the end of the steel bar, then use the sleeve machine to process the straight thread on the upsetting section of the end of the steel bar, and then use the connection cylinder to butt the two bars. By ten steel bar end cold heading, not only the cross-section is increased; but also the strength is improved. Plus, the minimum diameter of the bottom of the thread after the straight thread is processed on the end of the steel bar, should be not less than the diameter of the parent material of the steel bar. Therefore, the joint can be equal strength to the parent material of the steel bar.

The connection process of equal-strength straight-threaded reinforcement follows the standard process of construction and should not be changed at will in order to affect the actual quality of construction. In the construction process, there is inevitably cutting of the material, so the processing of the reinforcement should be scientifically and reasonably adjusted to ensure that it meets the construction specifications and standards. In particular, in the process of reinforcement upsetting, the operation should be standardized by professional equipment, and the most suitable processing pressure should be determined by conducting trial processing according to the relevant data and possible influencing factors before the formal processing.

The operation should be standardized, the processing angle should be carefully mastered and carefully checked in order to promote the actual effect of upsetting to be reliably guaranteed. It should be noted that in the actual construction process, it is strongly not allowed to upset the original upsetting reinforcement again. If it is found that the quality and effect of the upsetting reinforcement does not meet the relevant requirements, it needs to be cut out and reapplied to the upsetting operation.

In the thread processing, the threads are added one by one on the special thread sleeve machine and matched with the matching sleeve one by one, and those that pass the inspection go to the next process, and any qualified threads are removed. In order to ensure that the threads are damaged or operated during installation and transportation, they should be protected by sleeves or plastic caps in time.

In the process of steel connection, the connection sleeve is prefabricated in the factory according to the design specifications and accuracy and then boxed for use. In the field, the connection sleeve is used to connect the reinforcing steel and tighten it with a common wrench. In operation, attention should be paid to the degree of tightening, in general, the reinforcement joint without more than one buckle of the complete wire buckle exposed can be considered tightened.

  2.2 Material and machine equipment

①Steel should meet the requirements of the national standard “hot-rolled ribbed steel for reinforced concrete” (GBl499) and the requirements of the “remaining heat-treated steel for reinforced concrete” (GBl3014).
② sleeve and locking mother material should be used high-quality carbon steel or alloy structural steel, the material should comply with the provisions of GB699.
③Tools and equipment: cutting machine, wire snapping machine, common wrench, gauge, etc.

  2.3 Quality control and precautions

①Personnel participating in the construction of rolling straight threaded joints must have technical training and pass the examination before they can be licensed to operate.
②The end face of the reinforcing bar must be flat, and the material should be cut with an abrasive cutter. The end face should be bent and the horseshoe should be cut away to avoid damaging the cutter and affecting the quality of the fillet during processing. ③Steel processing should often add water-soluble cutting fluid, it is strictly prohibited not to use cutting fluid processing fillet.
④Steel to be processed must be tied to a good identification plate to avoid processing the wrong model. ⑤ The end of the wire head should wear a protective cap in time after processing and inspection to prevent the wire head from being damaged or contaminated by cement paste in the process of handling and installation construction. ⑥Check the length of the thread, the fullness of the thread type and the number of complete threads in the process of processing.

  2.4 Connection and inspection of straight threaded joints

2.4.1 Field connection of straight-threaded joints.
①When connecting reinforcement, the specifications of the reinforcement and the sleeve must be the same, and the fillets of the reinforcement and the sleeve must be clean and intact.
② When connecting reinforcement, the reinforcement should be screwed into the connection sleeve on the positive axis.
③After the connection is completed, the two threads should be tightened in the central position of the sleeve and the standard sleeve should not have more than one buckle of complete wire exposed at each end.

2.4.2 Quality inspection of straight-threaded reinforcing steel joints The performance inspection of straight-threaded reinforcing steel joints is divided into two categories: type inspection and construction site inspection, sleeve inspection for factory inspection and fillet inspection for processing site inspection. The type inspection includes one-way tensile, high strain repeated pulling and pressing, large deformation repeated pulling and pressing of strength, ultimate strain and residual deformation.

At the construction site, the appearance of straight-threaded steel joints should be checked in full according to the national standard “General Technical Specification for Mechanical Connection of Reinforcing Steel” (JGJl07), and the mechanical properties of straight-threaded steel joints should be tested by taking specimens. One-way tensile test, if a test piece fails, then double the sampling, that is, take 6 test lines for re-inspection, if there is still a test piece fails, then the acceptance batch is unqualified. With the rapid development of construction projects, rolling straight thread connection technology for steel reinforcement has enhanced the safety factor for a new generation of mechanical connection technology.


With the development of social economy and the progress of science and technology, the rolling straight thread connection technology has been more widely used in the construction of building construction, because of its own convenient operation, good joint strength and other advantages, the construction industry has received widespread attention. From the perspective of the actual situation of the construction of today’s situation, it is important to strengthen the practical application of the rolling straight thread connection technology for the long-term development of the construction industry.

Therefore, it is necessary to analyze the actual application of this technology to help promote the continuous improvement and development of this technology on the basis of the current development, so as to better play its actual value, promote the scientific and effective development of the construction industry, and overall promote the progress of the social economy.


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