New Progress of High Strength Bolt Connection Technology for Steel Structure

In the field of modern steel structure construction and engineering, high-strength bolt connection technology occupies a pivotal position. It is the key link to ensure the overall stability, safety and reliability of steel structure. With the continuous development of the construction industry in the direction of higher, larger span, more complex structural forms and more severe environmental conditions, the high-strength bolting technology of steel structure has also put forward unprecedented challenges and requirements. In recent years, under the synergistic promotion of material science, manufacturing process, automation technology and testing and monitoring methods, high-strength bolting technology has made a series of remarkable new progress.

1.Improvement of material performance

Traditional high-strength bolt materials are mainly medium carbon steel or alloy steel-based, and today, new high-strength bolt materials continue to emerge. By adding special alloying elements such as vanadium, niobium, titanium, etc., the microstructure of steel has been optimised, and its yield strength and tensile strength have been significantly improved to withstand greater loads. For example, the tensile strength of some new high-strength bolts can be more than 1200MPa, compared with the traditional bolts have been significantly improved. At the same time, the toughness and corrosion resistance of the material has also been improved, which makes the application of high-strength bolts in marine engineering, chemical facilities and other harsh environments more reliable, effectively extending the service life of the steel structure and reducing maintenance costs.

2.Intelligent installation process

With the arrival of Industry 4.0 era, the installation process of high-strength bolts for steel structure is moving towards the direction of intelligence. Automated tightening equipment has been widely used in the construction of large-scale steel structure projects. Using advanced sensor technology, these equipments can accurately control the tightening torque and preload force of bolts, avoiding the errors and inconsistencies that may be brought about by manual operation. For example, in bridge construction, automated tightening equipment can quickly and accurately complete the installation of a large number of bolts according to preset parameters, greatly improving construction efficiency and installation quality. In addition, intelligent monitoring systems based on Internet of Things (IoT) technology are also emerging, which can monitor the parameters of bolts in the installation process in real time, such as torque, corner, preload, etc., and transmit the data to a remote monitoring centre to achieve all-round control of the entire installation process. Once abnormalities are found, the system can issue timely alarms so that the construction personnel can make adjustments and treatments to ensure that each bolt connection meets the design requirements.

3.Innovation of non-destructive testing technology

In the quality inspection of high-strength bolt connections, non-destructive testing technology has made a major breakthrough. Traditional detection methods such as ultrasonic testing, magnetic particle testing, etc. Although to a certain extent can be found inside the bolt and surface defects, but there are problems such as limited detection accuracy and complex operation. Nowadays, emerging non-destructive testing technologies such as laser scattering interference technology, electromagnetic ultrasonic testing technology and so on began to emerge. Laser scattering interference technology using laser irradiation bolt surface scattering pattern changes to detect defects and stress distribution inside the bolt, with non-contact, high precision, full-field measurement and other advantages. Electromagnetic ultrasonic detection technology is through the electromagnetic coupling principle in the bolt to stimulate and receive ultrasonic waves, without the need for coupling agent, can achieve rapid detection of the bolt. The application of these new technologies greatly improves the accuracy and reliability of the detection of high-strength bolt connections, and provides powerful technical support for guaranteeing the quality of steel structure projects.

4.In-depth research on durability

During the long-term use of steel structure, high-strength bolt connection faces durability problems such as fatigue, relaxation and environmental corrosion. In recent years, the research on these problems has been deepening. In the fatigue performance research, through a large number of tests and numerical simulation, a more accurate fatigue life prediction model of high-strength bolted connection has been established, which can take into account a variety of factors, such as the load spectrum, bolt preload, material properties, etc. on the fatigue life, and provide a scientific basis for the maintenance and overhaul of the steel structure. In the research of anti-relaxation performance, new bolt anti-loosening devices and technologies have been developed, such as adopting special nut structure and applying anti-loosening coating, etc., which effectively reduces the relaxation rate of bolts during long-term use and ensures the tightness of the connection. Meanwhile, in terms of corrosion resistance, by improving the surface treatment process of bolts, such as the use of new anti-corrosion coating and plating technology, the corrosion resistance of bolts is enhanced, and its service life in harsh environments is extended.

To sum up, the new progress of steel structure high-strength bolt connection technology in materials, installation process, testing technology and durability research will further promote the steel structure engineering towards a safer, more efficient and durable direction, and provide a solid technical guarantee for the construction of modern buildings and infrastructures.