Application Status and Research Direction of Self-locking One-way Bolt Engineering

Abstract: Bolted joints are one of the main connections for steel structures. High-strength bolts and plain bolts are often used as fasteners. Since these two bolts require a large installation space for installation, they are not suitable for connecting closed-section members such as tubular or box-shaped members, and the one-side fastening bolts solve the problem of limited construction of conventional bolts. Through the use of self-locking one-way bolts in the main structure, enclosure structure and functional components, the domestic application status is studied, and the future research focus and development direction of the bolts are analyzed in combination with the problems encountered in practical applications.

Key words: self-locking one-way bolt; working principle; T-shaped joint node; application status; research direction

0 Preface

The discovery and application of self-locking unidirectional bolts make the connection between closed cross-section members such as rectangular steel pipe columns and steel beams no longer depend on traditional methods such as field welding or bolt-on connection, thus reducing the accuracy of steel factory processing and on-site construction. Requirements, effectively improve construction efficiency and construction quality.

At present, the self-locking one-way bolt connection node and its application are still in the early stage of research. The design rules, related design specifications and industry standards of self-locking one-way bolts have not been introduced, and the actual use of the project is not as popular as high-strength bolts and ordinary bolts. However, the self-locking one-way bolt has a wide range of use, quick and convenient installation, labor saving, no need for on-site welding, high pre-tightening force and tensile shear capacity, good corrosion resistance, beautiful connection form and stable product performance. The high quality and many other advantages will be recognized by the industry in the future and become one of the important connection forms of steel structure. The application of different bolts is shown in Figure 1.

a—Self-locking one-way bolt; b—normal or high-strength bolt.

Figure 1 Different bolt applications

In this paper, the application of self-locking one-way bolts in the current stage of engineering, combined with the shortcomings and advantages in its application, analyzes the future research direction and positioning of the bolts.

1 　 Self-locking one-way bolt working principle

Since 1994, Japan and some European countries have developed several types of more mature self-locking one-way bolt products. At present, the locking principle of self-locking one-way bolts mainly has the following three types: 1) Using the principle of expansion bolts, the sleeve outside the screw is opened when the screw is tightened, and the connected parts are locked, such as Hollo- of the British Lindiper company. Bolt[1], BoxBolt type one-way bolt of LNA Solution Company of the United States. 2) When the nut is rotated on the screw, the screw moves forward relative to the screw, and the sleeve outside the screw is squeezed and deformed, and the cross-sectional area becomes large, forming a gasket to catch the connected member, such as the Ultra-Twist in the United States and Japan. . 3) A certain device is placed on the screw, and the device is opened to become a gasket after passing through the bolt hole, thereby locking the connected member, such as Australia's ONESIDE Fastener, the screw is provided with a foldable gasket, and the bolt hole is passed from one side. The post is opened into a normal gasket to form a connection similar to a normal high-strength bolt.

Xu Yanbin et al., with reference to the construction principle of the first type of unidirectional bolt, developed a self-locking one-way bolt (Fig. 2) by improving the sleeve material and the end structure [2], the working principle is shown in Figure 3, and its performance It is comparable to the London-based Lindoper's Hollo-Bolt, but at a lower cost. At present, two kinds of self-locking one-way bolts of grades 8.8 and 10.9 have been developed, and the mechanical properties such as tensile ultimate strength and shear ultimate strength of one-way bolts have been determined through experiments [3-4].

1 - gasket; 2 - sleeve; 3 - vertebra; 4 - high-strength screw; 5 - rubber gasket.

Figure 2 Self-locking one-way bolt

Figure 3 Self-locking one-way bolt working principle

2 　 Application Status of Self-locking One-way Bolt T-Joint Joints

Self-locking one-way bolts are used in engineering projects because of their unique advantages. Although the use of one-way bolts is still in the initial stage, self-locking is used for the main structure, the envelope structure and the functional components. One-way bolt [5-7].

2.1 Main structure of the building

The main structure of the building generally includes a beam-column connection node, a column-column connection node, and the like. If the steel column is a closed section such as a rectangular shape, due to the limitation of the construction space, the conventional high-strength bolt and the ordinary bolt cannot be directly used in the column-column connection of the rectangular steel pipe column and the H-shaped steel beam and the closed column. Special bolts are required for bolting. Previously used in domestic engineering projects, special bolts that can run through the entire rectangular steel pipe column, commonly known as pairs of bolts. On the one hand, the bolt-type connection node has a large weakening of the column section due to the opening on both sides of the column wall; on the other hand, the precision requirements for the beam-column factory processing and on-site construction are high, and the construction efficiency is followed. reduce. These two drawbacks have caused the use of this type of bolt to be severely limited, so it has not been widely used in engineering.

The development and application of self-locking unidirectional bolts have made the selection of fasteners for rectangular steel pipe columns and H-shaped steel beam joints (Fig. 4). The construction process is very simple, including: 1) opening the component at the joint; 2) aligning the bolt hole of the connector; 3) inserting the self-locking one-way bolt; 4) tightening with an electric wrench.

Figure 4 One-way bolt is applied to the H-beam and the rectangular steel pipe end plate connection

A common method for column-column splicing of closed-section columns in domestic engineering projects is flanged connections, similar to the way pipe connections are made. The flange connection has the advantages of convenient disassembly, high strength, good sealing performance, etc., but also has the disadvantage of protruding the column section. The application of the self-locking one-way bolt not only makes the column-column connection node beautiful (Fig. 5), but also has excellent bearing performance. The bolt installation method and construction procedure are similar to the beam-column connection node and will not be described again.

Figure 5 One-way bolts for column-column connections

2.2 Building exterior wall and envelope structure

a - overall; b - local.

Figure 6 One-way bolt is applied to the outer wall of the skeleton and the tubular member of the main structure

Skeleton wall is a wall that is filled or suspended between a frame or a frame beam and supported by a frame or a frame. It is used in multi-storey, high-rise civil buildings and industrial buildings. The construction of the external wall dry-hanging granite and the like has the advantages of being unaffected by the season and avoiding the penetration of the saline-alkali pigment on the stone during the wet work grouting. Dry-hanging granite plates are mainly fixed by steel skeletons. According to the design drawings, the main keel spacing requirements are first installed on the main structure. For the case where the outer wall of the skeleton is connected with the tubular member of the main structure, the conventional practice in the country is to use the welding method to construct and install the keel. After the welding is completed, the welding slag is removed and two antirust paints are painted. Although the welding method is safe and reliable, it is extremely rust-resistant and difficult to adjust twice after installation, so the construction accuracy is very high. At present, there are engineering cases in China that use self-locking one-way bolts as fasteners for connecting the outer wall of the skeleton with the tubular members of the main structure (Fig. 6), thereby eliminating on-site welding, improving construction efficiency and quality, and achieving fast and efficient assembly. Construction, and the nodes are stable and reliable.

2.3 Glass curtain wall and roof

The glass curtain wall refers to the load that can be displaced from the main structure by the supporting structure system, and does not share the load of the building outer structure or the decorative structure that the main structure bears, and is composed of glass, metal connecting parts and supporting system.

As a component that directly transmits various loads to the glass panel to the main structure of the building, the supporting system needs to be effectively connected with the main structure to meet its function. Since the glass needs to be mounted on a flat and non-angular base layer, it is required that the joint between the support system and the main structure does not have a protrusion similar to a flange. The self-locking one-way bolt can effectively avoid this problem and is suitable for the connection between the glass curtain wall support system and the tubular structure of the main structure (Fig. 7, Fig. 8).

Figure 7 Example of a one-way bolt applied to a glass curtain wall installation

a - overall; b - local.

Figure 8 One-way bolts for glass curtain wall installation

Steel structure roofing is widely used in industrial and civil buildings due to its simple construction, short construction period and durability. Due to its high strength and toughness, it is suitable for single-story and long-span buildings. It can be used to build multi-storey or high-rise buildings. building. When the steel truss with a square tube closed section is used for the roof, the common bolt connection has the problem of limited construction, and it can only rely on welding or pulling bolts, etc., which brings various drawbacks to the construction. The use of self-locking unidirectional bolts currently solves this problem, making it widely used in closed section steel component connections (Figure 9).

Figure 9 One-way bolt applied to the steel truss connection of the square tube closed section

2.4 stairs and handrails

The backyard area of ​​the theme park usually has more stair platforms for operation and maintenance, horse tracks, etc. Many outdoor civil buildings also have outdoor steel structure stairs, which need to be installed with railings to meet safety requirements and functions. When a closed section member is used for a stair or a horseway structural support member, only the end plate of the railing column and the steel beam are welded or the bolts are connected. According to the load-deformation curve of the shear force obtained by the self-locking one-way bolt shear test made by Tongji University, it can be known that [3-4]: the mechanical properties of the one-way bolt are excellent in shear strength and strength, due to one-way The bolt is provided with a sleeve, which has better shear resistance than ordinary bolts. Therefore, it is very suitable to use the one-way bolt as a fastener to connect the railing handrail with the tubular structure, and the advantage of the shear bearing performance of the one-way bolt can be fully utilized, as shown in FIG.

a - overall; b - local.

Figure 10 One-way bolts are used to connect railings to tubular structures.

Through the analysis of the above engineering examples, it can be seen that the self-locking unidirectional bolts are suitable for the connection of all components and closed section members, not only satisfying the structural bearing capacity and other performance requirements, but also meeting the architectural aesthetic requirements. However, special attention should be paid to the construction requirements of self-locking one-way bolts. For example, when M16 and M20 one-way bolts are used, the thickness of the outer layer should not be less than 8 mm, and the rubber gasket is indispensable; It needs to be flush and close; the torque must be set to the specified value during installation.

3 　 Research direction of self-locking bolts

Self-locking one-way bolts have broad application prospects. However, the current theoretical research on self-locking one-way bolts in China is not mature enough to provide sufficient reference for engineering design. Therefore, the author believes that the future research on self-locking unidirectional bolts includes but is not limited to the following aspects. 3.1 Development of new one-way bolts

Up to now, there are only 4 kinds of domestic STUCK-BOM one-way bolts with M16 and M20 specifications of 8.8S and 10.9S in China, and the models are less than enough to meet the requirements of all projects. As a result, the one-way bolts are limited in the use of special structures such as oversized steel structures and complex profiled steel structures, and more types of one-way bolts need to be developed according to existing principles to meet engineering requirements.

3.2 Develop node design basis

The design of the node design manual [1] developed by the British Steel Structure Association proposes the design of the connection between the rectangular steel pipe column and the H-beam end plate using the one-way bolt (Hollo-Bolt), but only provides the inner end of the one-way bolt. The design criterion of the plate joint node does not involve the calculation method of the one-way bolt for the bearing capacity of the semi-rigid connection node of the overhanging end plate. Moreover, the design proposal for the one-way bolt in the above node design manual is based on the Hollo-Bolt one-way bolt, and can not fully guide the design and use of the domestic STUCK-BOM one-way bolt. Therefore, there is still a lack of research on the force performance of the connected node system, which makes the one-way bolted joint node lack of theoretical basis in the actual project.

3.3 Analysis of the difference between ordinary bolts and high-strength bolts

According to the test results of the bearing capacity of the self-locking one-way bolt T-shaped joints of Li Guoqiang et al. [8], comparing the theoretical calculation results of the bearing capacity of the joints of the same parameters with high-strength bolts and ordinary bolts, the self-locking single is known. The force applied to the bolted joints should be between the high-strength bolts of the same size and the normal bolt joints. However, it has not been specifically analyzed which bolts are more likely to be subjected to the force of the one-way bolts. Related design procedures lead to simplified design recommendations for unidirectional bolts.

3.4 Proposed unidirectional bolt node construction requirements

In order to let the designer understand the design requirements of the self-locking one-way bolt in a simple and efficient way, further theoretical analysis and a lot of experiments are needed to summarize the construction requirements of the self-locking one-way bolt node, and to illustrate a certain form in an easy-to-understand form. The type of bolt is suitable for the connected parts, thus reducing the amount of calculations by the designer.

3.5 Integrating self-locking one-way bolts into structural design software

At present, there are many structural design softwares, which bring great convenience to structural designers, and all beams, columns, connectors, contact forms, etc. exist in the form of parameters in the software to facilitate the use of designers. However, the self-locking one-way bolt has not been integrated into the structural design software, which is not convenient for structural calculation. Therefore, after the above four studies are mature, the one-way bolts can be integrated into the structural design software in a parametric form to complete the entire design chain.

4 　 Conclusion

Self-locking unidirectional bolts are trusted and praised by engineers for their unmatched wide applicability. In the future, they can be used as important fasteners in steel structure joints like ordinary bolts and high-strength bolts. The author believes that self-locking one-way bolts still have a lot of research space and development space, and it is necessary to improve relevant design specifications and standards, so as to maximize the promotion and use of one-way bolts.

references:

[1] Lindapter International. Hollo-Bolt [M]. Yorkshire, UK: Lindiper International, 1995.

[2] Xu Yanbin, Li Guoqiang, Zhang Long. Single-sided fastening bolt: China, 201210435247.7[P]. 2012-11-05.

[3] Li Guoqiang, Zhang Jiehua. Study on bearing capacity of self-locking unidirectional bolts for 8.8 grade steel structures [D]. Shanghai: Tongji University, 2015.

[4] Li Guoqiang, Zhang Jiehua. Study on bearing capacity of self-locking one-way bolts for 10.9 grade steel structures [D]. Shanghai: Tongji University, 2016.

[5] Zhang Liang, Chen Yiyi. Comment on the connection form of square steel tubular column and H-shaped steel beam [J]. Structural Engineer, 2009, 25(4): 129-137.

[6] Wang Meng, Wang Yan, Chai Wei, et al. Study on the effective length and bearing capacity of equivalent T-pieces of European standard EC3 high-strength bolts [J]. Progress in Construction Steel Structure, 2009, 11(3): 58-62.

[7] Guo Bing, Liu Feng, Gu Qiang. Failure mode and bending moment relationship of beam-column end plate connection[J]. China Civil Engineering Journal, 2002, 35(5): 24-27.

[8] Li Guoqiang, Duan Lian. Experimental and theoretical study on bearing capacity of one-way bolted joints of H-beam and rectangular steel tubular columns with extended end plates[J]. Journal of Building Structures, 2015, 36(9): 91-100 .

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