# Application of Intelligent Technology on Tunnel Steel Structure Factory

Authors: Chenyang He
Journal: Mathematical Problems in Engineering
 (2022)

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## Abstract

At present, the construction of tunnel steel structure factories has been common, but most of them are still on the low end. In addition, the manual processing modes face certain problems, such as high waste rate, low efficiency, and discrete welding of steel components. To address these problems, this paper introduces an intelligent management cloud platform, aiming to realize unmanned control methods and construct an intelligent tunnel steel component processing plant. There are four main production lines in the intelligent steel structure factory. First, an intelligent production line of a tunnel grille arch effectively improves the production efficiency, production quality, and dust removal effect of the grille arch through the automatic welding technology of a reinforcement mechanism-based welding robot. Second, a processing line of a steel pipe for tunnel construction improves the overall processing efficiency, saves costs, and reduces work intensity by using an intelligent numerical control system, a pneumatic clamping device, a plasma cutting hole assembly, and a 360-degree automatic rotation system. Third, an automatic feeding platform of section steel arch production line adopts the six-axis robot sensor clamping connecting plate positioning and six-axis robot sensing three-plane automatic welding system, which not only compensates for the defects of manual production but also realizes the reduction, increases efficiency, and improves welding quality and precision. Fourth, an automatic steel mesh production line saves much labor and enhances site management and production efficiency through vertical and horizontal reinforcement pay-off racks. Overall, in this study, the construction goals of informatization, intellectualization, and personnel downsizing of the tunnel steel structure processing have been achieved.


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## Body

## 1. Introduction

As underground technology, tunnel engineering involves a variety of underground structures and construction methods and techniques. The development of construction methods and technologies is related to the design and characteristics of underground structures. With the widespread use of tunnels, an increasing number of advanced small pipes and pipe roofs have been used. Most of the current applications use the punching and pinching machines separately, which consumes much space. Moreover, the corresponding processing steps are also separated. Manual feeding, punching, pinching, and blanking have certain defects, such as much manpower, high labor intensity, slow processing speed, and low efficiency.Considering the design and construction of an intelligent steel bar processing plant scheme, intelligent production technology, and the theory of steel bar cutting compensation, Liu Yang [1] developed a complete modern high-speed railway steel bar engineering intelligent manufacturing technology system. Further, by analyzing the intelligent processing of steel bars, Sun Yi and Zhou Lei [2, 3] reduced the number of personnel from 50 to 12, achieving a 100% pass rate for semifinished and finished products. Through the overall layout and planning analysis of a steel bar processing plant, Yu Xiaofeng and Jia Antong et al. [4, 5] realized the processing mode of overall planning, rational layout, and land saving with an emphasis on practicality and compliance with standards. Wang Wei et al. [6] studied the optimization management of steel bar processing and improved the utilization rate of steel bars. In terms of intelligent steel bar processing, Zhao Menghe [7] explored the factory management mode of steel bar processing plants, which fundamentally solved the problem of insufficient technical manpower and realized a significant reduction in mechanical equipment investment, raw material waste, and construction costs. Product quality, cost efficiency, production flexibility, and enhancement of industrial performance denote targets of intelligent manufacturing vision [8], which poses new challenges to the development of automation and industrial IT solutions. In particular, the availability of semantic description of data and data sources aligned with product, production, and process information has been a necessary condition for the realization of objectives [9]. To satisfy growing demands, traditional manufacturing techniques have been forced to develop and adapt to new practices and methods for planning, control, and parameter optimization [10]. The research and development of optimization techniques have transformed traditional manufacturing methods into intelligent manufacturing methods that can manufacture high-quality products at a lower cost and a faster production rate [11]. Masny Wojciech [12] developed a generic ontology-based approach for semantic modeling of data sources, establishing the basis for seamless information exchange. Recently, many artificial intelligence-based techniques have been designed for capturing, representing, organizing, and utilizing knowledge by computers, and they play an important role in intelligent manufacturing [13–15]. Zillner [16] presented an innovative hybrid system for selecting the best parameters for tuning in an open loop PID controller. This system combines a rule-based system and artificial neural networks.Robot adaptive welding refers to a robot with a sensing function that can automatically detect environmental changes, adaptively adjust the welding process and robot path, and finally realize intelligent welding. Currently, the main methods of robot collision-free path planning are the free space method based on the C space and the artificial potential field method [17–19]. Zhuang et al. [20–23] and D. W. Kim [24] studied the welding path planning problem when a six-degree-of-freedom robot and a two-degree-of-freedom positioner coordinated welding.Considering the management requirements for mechanization, specialization, factorization, and intelligence and the goal of lean management and intelligent construction, an intelligent management cloud platform is introduced to strengthen process control and construct an intelligent tunnel steel component processing plant comprehensively [25–27]. Each workshop in the processing plant is divided into four areas, namely, the finished product area, processing area, raw material storage area, and transportation area in accordance with the principle of scientific zoning and reasonable layout. In addition, the processing plant adopts the four most advanced domestic intelligent production lines, namely, the grille arch production line, CNC (computer numerical control) mesh welding production line, section steel arch production line, and small catheter production line. The construction goals of informatization, intelligence, and personnel downsizing of tunnel steel structure processing are realized [28–31]. The development of this production line is described in detail in the following.


## 2. Implementation Steps of Intelligent Production Line

Currently, intelligent production technology has been gradually introduced in the process of production and processing of steel structures, which has significantly improved the analysis and processing of a structural system, as well as the quality standard [32, 33]. In this regard, this paper optimizes the traditional design concept. At the macro level, robotic intelligent production lines are established to replace traditional manual mechanical manufacturing. In the process, fast production steps are set, and the construction and production are performed according to the path specified by the program [34–37]. The purpose of the unmanned workshop is achieved through remote control programming.By optimizing the overall layout and design of the four production lines in a tunnel reinforcement factory, each production line can achieve streamlined operations and overall layout [38, 39]. Through the programming of implementation steps of the four production lines, process intellectualization is achieved [40, 41]. The automation of a production line can be realized through the automatic setting of each process’s connection. On this basis, the remote control function can be provided by programming the control program. At present, automatic robot welding has made significant progress [42–45]. By using the robotic automatic welding, a factory line can be controlled remotely. The intelligent control programming of the four production lines, including the global startup, automatic start of feeding, automatic start of the arch bending machine, automatic start of the back end, automatic start of connecting plate feeding, emergency stop, and error reset, is performed separately. The specific procedure is given in Appendix 1.The programming is practically applied to the field. Through the remote control of equipment, an unmanned workshop is realized. In this type of workshop, only one person is required to make a safety tour of the workshop. As shown in Figure1, the interface is constructed from the aspects of the production plan and processing quantity to improve production efficiency.Figure 1
Remote control interface illustration.


## 3. Reinforcement Yard Intelligent Production Line

### 3.1. Grille Arch Intelligent Production Line

In the traditional production line, different pieces of equipment, such as the cutting machine, punching machine, I-beam cold bending machine, and welding machine, are usually placed separately during the production and processing of a section steel arch connecting plate, which consumes much space. Moreover, the corresponding processing procedures are performed separately, which requires manual operations to perform different types of processing, such as feeding, cutting, punching, section steel blanking, section steel cold bending, and welding sequentially. This type of production method has the shortcomings of high labor demand, low automation degree, high labor intensity, slow processing speed, and poor work efficiency. To address these shortcomings, this paper optimizes and improves the grille arch production.An intelligent automatic numerical control eight-bar hoop bending machine and a grille steel welding robot for figure eight bending, extrusion, and welding have been introduced in a grille arch production line. Through the digital program control technology, a robot welds the predetermined workpiece using a customized mould and the set running track program, thus realizing digitization, intelligence, and automation and then improving the welding quality and work efficiency. The mould can be turned by 180° to realize the 360° welding without a dead angle. The eight-bar all-in-one forming machine can automatically complete the integrated automatic functions of fixing, cutting, bending, welding, and forming steel bars in accordance with the requirements using the numerical control programming. The standardization and unification of dimensions are conducive to the improvement in the production efficiency and production quality of a grille arch. In addition, manpower is reduced from six to nine people in the traditional grille arch production to three people in the optimized production. Furthermore, the production efficiency is improved significantly, from processing 350 eight-bar grille arches to 2,000 eight-bar grille arches in an eight-hour period as shown in Figure2.Figure 2
1: Eight-bar material charging table; 2: V-shaped conveying roller; 3: reinforcement mechanism; 4: eight-bar production line; 5: eight-bar finished product heat-resistant conveyor; 6: eight-bar welding robot; 7: grille arch welding robot; 8. grille arch welding tooling.To solve the problem of dust in an intelligent production line of a tunnel grille arch, the set dust removal structure can make the suction head rotate and drive the second sphere to rotate synchronously, thus effectively improving the dust removal range and effect as shown in Figure3.Figure 3
The grille arch intelligent production line.Through the production line optimization, production efficiency is increased significantly compared with the traditional production methods, namely, from processing 350 eight-bar grille arches to 2,000 eight-bar grille arches in an eight-hour period. In addition, the efficiency is improved by five to ten times, and the personnel is reduced to only one person.


### 3.2. Steel Pipe Processing Production Line

With the widespread use of tunnels, an increasing number of small pipes and pipe roofs have been used. Most of the current applications place the punching and pinching machines separately, which is space-consuming, and the processing steps are performed separately. Manual feeding, punching, pinching, and blanking have defects of much manpower consumption, high labor intensity, slow processing speed, and low efficiency. To solve these problems, a fully automatic processing line is proposed.The proposed production line adopts an intelligent numerical control system, a pneumatic clamping device, a plasma cutting hole assembly, a 360° automatic rotation system, a charging table, a conveying mechanism, and a pinching machine. An AC synchronous servo motor with a large torque has the characteristics of fast response, high positioning accuracy, low noise, small braking heat loss, and long service life. Further, an advanced PLC controller adopts a simple and convenient touch screen operation. After completing the program setting, automatic processing, including automatic hole cutting, conveying, and tip reduction, is performed as shown in Figure4.Figure 4
1: Transfer conveyor assembly; 2: blanking rack; 3: pinching machine assembly; 4: plasma cutting hole assembly; 5: loading rack plate.After cutting holes, a small catheter is conveyed to the conveying mechanism. The feeding device feeds the steel pipe to the conveying mechanism on the side of the pinching machine. Then, the conveying mechanism sends the small catheter to the pinching machine. When the small catheter hits the positioning baffle, the clamping mechanism of the automatic feeding rack clamps the small catheter. Afterward, the positioning stopper is pulled up by the cylinder. Once the medium-frequency solid-state heater heats the steel pipe, until it turns white, the feeding rack inserts the steel pipe into the pinching machine. The machine drives the mold to rotate through mechanical transmission. The mold extrudes the steel pipe through its own special structure to make it have the required shape. After the tip reduction is completed, the small catheter is transported back in the reverse direction and, finally, automatically blanked to the blanking rack as shown in Figure5.Figure 5
The steel pipe processing intelligent production line.The loading rack plate and feeding control plate can realize automatic feeding of steel pipes, thus improving the overall processing efficiency; conduits of up to 12 m can be processed. The processed catheter with a diameter of 42 mm–108 mm can meet the needs of small catheters of various sizes, which can further reduce costs, space, manual labor, and work intensity.


### 3.3. Section Steel Arch Connecting Plate Automatic Production Line

The section steel arch plays an important role in the initial support of a tunnel. Generally, the production process of the traditional tunnel section steel arch requires manual welding of an eight-bar and the entire grille arch and has the disadvantages of slow processing, low efficiency, and a poor forming effect. Through systematic research, the production of a tunnel section steel arch is optimized and improved.A section steel arch is bent with a section steel bending machine. The Siemens controller and touch screen have powerful functions and superior performances, such as one-key operation and scheduled shutdown. A 3D camera of an H-section steel arch end plate automatic welding robot can automatically identify the weld seam and perform the 360° automatic welding, thus improving the welding quality and ensuring the consistency of the welding effect. The connecting plate production line includes hydraulic shearing and punching machines, which realize shearing and four-hole punching integrated molding through a simple, convenient, and efficient operation. The production process from raw materials to the connecting plate products does not require turnaround processes and sites, which not only reduces labor intensity but also increases production efficiency by 10 times compared to the traditional production. The traditional single-hole forming produces 300 connecting plates per day (i.e., for eight hours), while the proposed improved technology can produce 3,000 connecting plates for the same time. In addition, the traditional processing of the four-hole center distance is inaccurate, and the connecting error is large, but in the optimized processing, four holes are integrally stamped and formed with an accurate size as shown in Figure6.Figure 6
The section steel arch intelligent production line.An automatic feeding platform of the section steel arch production line for cold bending and cutting of section steel includes six-axis robot sensor clamping connecting plate positioning and a six-axis robot sensing three-plane automatic welding system which break through the manual production method. This can effectively reduce personnel and costs while enhancing production efficiency. In more detail, the number of required personnel is reduced from the traditional three to six people to only one person. The robot adopts the three-bit plane sensing position finding, which has the characteristics of high welding quality and precision. The positioner jaws can be turned by 180°, enabling 360° welding without dead ends. The robot walking device can be linked with the welding system and automatically adjusts the working position of a robot, thus meeting the welding needs of industrial steel of different lengths. A jaw welding positioner can provide the required welding position for the welding of the steel, and the clamping position can be adjusted according to the steel length to meet the welding needs of different steel specifications.


### 3.4. Automatic Steel Mesh Production Line

In the traditional mode of simple reinforcement mesh processing, mesh welding requires a large number of molds to be created. In addition, each time the specification is changed, the corresponding mold needs to be remade. Moreover, welding is performed in the manual mode. Thus, the mesh welding quality cannot be guaranteed, and the over-reliance on tooling and labor in the production process lead to the inability to guarantee the machining quality and timely delivery of reinforcement mesh. As labor costs continue to increase, the assembly line is optimized to automate production, which accelerates progress and ensures construction quality.The automatic steel mesh production line includes vertical and horizontal reinforcement pay-off racks. The vertical reinforcement pay-off rack has a prestraightening part of vertical reinforcement on one side. The prestraightening part of vertical reinforcement is connected with a vertical reinforcement traction storage device, which is connected with the welding host part. The welding host part is connected with a straightening traction part of the horizontal reinforcement and mesh shearing device. Automatic control is achieved through automatic welding and feeding technology as shown in Figures7 and 8.Figure 7
Disc reinforcement pay-off frame.Figure 8
Welding host.


## 3.1. Grille Arch Intelligent Production Line

In the traditional production line, different pieces of equipment, such as the cutting machine, punching machine, I-beam cold bending machine, and welding machine, are usually placed separately during the production and processing of a section steel arch connecting plate, which consumes much space. Moreover, the corresponding processing procedures are performed separately, which requires manual operations to perform different types of processing, such as feeding, cutting, punching, section steel blanking, section steel cold bending, and welding sequentially. This type of production method has the shortcomings of high labor demand, low automation degree, high labor intensity, slow processing speed, and poor work efficiency. To address these shortcomings, this paper optimizes and improves the grille arch production.An intelligent automatic numerical control eight-bar hoop bending machine and a grille steel welding robot for figure eight bending, extrusion, and welding have been introduced in a grille arch production line. Through the digital program control technology, a robot welds the predetermined workpiece using a customized mould and the set running track program, thus realizing digitization, intelligence, and automation and then improving the welding quality and work efficiency. The mould can be turned by 180° to realize the 360° welding without a dead angle. The eight-bar all-in-one forming machine can automatically complete the integrated automatic functions of fixing, cutting, bending, welding, and forming steel bars in accordance with the requirements using the numerical control programming. The standardization and unification of dimensions are conducive to the improvement in the production efficiency and production quality of a grille arch. In addition, manpower is reduced from six to nine people in the traditional grille arch production to three people in the optimized production. Furthermore, the production efficiency is improved significantly, from processing 350 eight-bar grille arches to 2,000 eight-bar grille arches in an eight-hour period as shown in Figure2.Figure 2
1: Eight-bar material charging table; 2: V-shaped conveying roller; 3: reinforcement mechanism; 4: eight-bar production line; 5: eight-bar finished product heat-resistant conveyor; 6: eight-bar welding robot; 7: grille arch welding robot; 8. grille arch welding tooling.To solve the problem of dust in an intelligent production line of a tunnel grille arch, the set dust removal structure can make the suction head rotate and drive the second sphere to rotate synchronously, thus effectively improving the dust removal range and effect as shown in Figure3.Figure 3
The grille arch intelligent production line.Through the production line optimization, production efficiency is increased significantly compared with the traditional production methods, namely, from processing 350 eight-bar grille arches to 2,000 eight-bar grille arches in an eight-hour period. In addition, the efficiency is improved by five to ten times, and the personnel is reduced to only one person.


## 3.2. Steel Pipe Processing Production Line

With the widespread use of tunnels, an increasing number of small pipes and pipe roofs have been used. Most of the current applications place the punching and pinching machines separately, which is space-consuming, and the processing steps are performed separately. Manual feeding, punching, pinching, and blanking have defects of much manpower consumption, high labor intensity, slow processing speed, and low efficiency. To solve these problems, a fully automatic processing line is proposed.The proposed production line adopts an intelligent numerical control system, a pneumatic clamping device, a plasma cutting hole assembly, a 360° automatic rotation system, a charging table, a conveying mechanism, and a pinching machine. An AC synchronous servo motor with a large torque has the characteristics of fast response, high positioning accuracy, low noise, small braking heat loss, and long service life. Further, an advanced PLC controller adopts a simple and convenient touch screen operation. After completing the program setting, automatic processing, including automatic hole cutting, conveying, and tip reduction, is performed as shown in Figure4.Figure 4
1: Transfer conveyor assembly; 2: blanking rack; 3: pinching machine assembly; 4: plasma cutting hole assembly; 5: loading rack plate.After cutting holes, a small catheter is conveyed to the conveying mechanism. The feeding device feeds the steel pipe to the conveying mechanism on the side of the pinching machine. Then, the conveying mechanism sends the small catheter to the pinching machine. When the small catheter hits the positioning baffle, the clamping mechanism of the automatic feeding rack clamps the small catheter. Afterward, the positioning stopper is pulled up by the cylinder. Once the medium-frequency solid-state heater heats the steel pipe, until it turns white, the feeding rack inserts the steel pipe into the pinching machine. The machine drives the mold to rotate through mechanical transmission. The mold extrudes the steel pipe through its own special structure to make it have the required shape. After the tip reduction is completed, the small catheter is transported back in the reverse direction and, finally, automatically blanked to the blanking rack as shown in Figure5.Figure 5
The steel pipe processing intelligent production line.The loading rack plate and feeding control plate can realize automatic feeding of steel pipes, thus improving the overall processing efficiency; conduits of up to 12 m can be processed. The processed catheter with a diameter of 42 mm–108 mm can meet the needs of small catheters of various sizes, which can further reduce costs, space, manual labor, and work intensity.


## 3.3. Section Steel Arch Connecting Plate Automatic Production Line

The section steel arch plays an important role in the initial support of a tunnel. Generally, the production process of the traditional tunnel section steel arch requires manual welding of an eight-bar and the entire grille arch and has the disadvantages of slow processing, low efficiency, and a poor forming effect. Through systematic research, the production of a tunnel section steel arch is optimized and improved.A section steel arch is bent with a section steel bending machine. The Siemens controller and touch screen have powerful functions and superior performances, such as one-key operation and scheduled shutdown. A 3D camera of an H-section steel arch end plate automatic welding robot can automatically identify the weld seam and perform the 360° automatic welding, thus improving the welding quality and ensuring the consistency of the welding effect. The connecting plate production line includes hydraulic shearing and punching machines, which realize shearing and four-hole punching integrated molding through a simple, convenient, and efficient operation. The production process from raw materials to the connecting plate products does not require turnaround processes and sites, which not only reduces labor intensity but also increases production efficiency by 10 times compared to the traditional production. The traditional single-hole forming produces 300 connecting plates per day (i.e., for eight hours), while the proposed improved technology can produce 3,000 connecting plates for the same time. In addition, the traditional processing of the four-hole center distance is inaccurate, and the connecting error is large, but in the optimized processing, four holes are integrally stamped and formed with an accurate size as shown in Figure6.Figure 6
The section steel arch intelligent production line.An automatic feeding platform of the section steel arch production line for cold bending and cutting of section steel includes six-axis robot sensor clamping connecting plate positioning and a six-axis robot sensing three-plane automatic welding system which break through the manual production method. This can effectively reduce personnel and costs while enhancing production efficiency. In more detail, the number of required personnel is reduced from the traditional three to six people to only one person. The robot adopts the three-bit plane sensing position finding, which has the characteristics of high welding quality and precision. The positioner jaws can be turned by 180°, enabling 360° welding without dead ends. The robot walking device can be linked with the welding system and automatically adjusts the working position of a robot, thus meeting the welding needs of industrial steel of different lengths. A jaw welding positioner can provide the required welding position for the welding of the steel, and the clamping position can be adjusted according to the steel length to meet the welding needs of different steel specifications.


## 3.4. Automatic Steel Mesh Production Line

In the traditional mode of simple reinforcement mesh processing, mesh welding requires a large number of molds to be created. In addition, each time the specification is changed, the corresponding mold needs to be remade. Moreover, welding is performed in the manual mode. Thus, the mesh welding quality cannot be guaranteed, and the over-reliance on tooling and labor in the production process lead to the inability to guarantee the machining quality and timely delivery of reinforcement mesh. As labor costs continue to increase, the assembly line is optimized to automate production, which accelerates progress and ensures construction quality.The automatic steel mesh production line includes vertical and horizontal reinforcement pay-off racks. The vertical reinforcement pay-off rack has a prestraightening part of vertical reinforcement on one side. The prestraightening part of vertical reinforcement is connected with a vertical reinforcement traction storage device, which is connected with the welding host part. The welding host part is connected with a straightening traction part of the horizontal reinforcement and mesh shearing device. Automatic control is achieved through automatic welding and feeding technology as shown in Figures7 and 8.Figure 7
Disc reinforcement pay-off frame.Figure 8
Welding host.


## 4. Advantages and Effects of Intelligent Production

The traditional grille arch production requires nine people, which is reduced to only one person by introducing intelligent production. In addition, the traditional method can process 350 eight-bar grille arches per day, while the optimized method can process 2,000 eight-bar grille arches per day. The traditional reinforcement mesh production line requires six people, but the optimized one requires only one person. Further, the traditional method can process 200 profiled steel arches per day, while the optimized one can process 1,400 of them. The traditional section steel arch production line requires six people, whereas the optimized one requires only one person. The traditional and optimized methods can produce 300 and 3,000 pieces of reinforced meshes per day, respectively. The traditional small catheter production line requires two people, but the optimized production requires one person. The traditional method can process 100 small catheters per day, but the optimized method can process 1,000 of them. The details are shown in Table1 and Figures 9 and 10.Table 1
Comparison of the traditional and optimized production lines.
Production line typePersonnelProductivityProduction lineTraditionOptimizedTraditionOptimizedGrille arches913502000Profiled steel arch612001400Reinforced mesh613003000Small catheter211001000Figure 9
Comparison of personnel before and after line optimization.Figure 10
Comparison of efficiency before and after production line optimization.The intelligent steel bar processing production line can effectively solve the problem of steel bar processing. Through unified preparation of steel bar processing, unified optimization, cutting material checking, unified acceptance of steel bars entering and leaving the site, and unified deployment of vehicles, the steel bar processing efficiency is improved, the steel bar processing quality is guaranteed, and the waste of materials is reduced. In addition, in the process of improving daily management, construction costs are saved as shown in Figures11 to 12, 13, 14.Figure 11
Section steel arch finished product.Figure 12
Mesh finished product.Figure 13
Grille arch finished product.Figure 14
Small catheter finished product.


## 5. Conclusion

This paper presented the research on the overall technology of an intelligent steel bar processing plant. The main contributions of this work can be summarized as follows:(1)
The reinforcement yard intelligent production software is developed to realize unmanned workshop and thus reduces labor amount, improves construction efficiency, and ensures construction quality(2)
An intelligent production line of a tunnel grille arch, which can effectively improve the production efficiency and quality of a grille arch, is constructed using automatic welding technology of a reinforcement mechanism welding robot. By adopting a dust removal structure, the dust removal range and effect are effectively improved(3)
The processing line of a steel pipe for tunnel construction using the intelligent numerical control system, pneumatic clamping device, plasma cutting hole assembly, and 360° automatic rotation system, which can improve the overall processing efficiency, save costs, reduce site occupation and manual handling, as well as work intensity, is presented(4)
The automatic feeding platform of a section steel arch production line adopts the six-axis robot sensor clamping connecting plate positioning and six-axis robot sensing three-plane automatic welding system, which not only compensates for the defects of manual production but also reduces efficiency and improves welding quality and precision(5)
The automatic steel mesh production line, which can save much labor and enhance site management and production efficiency through vertical and horizontal reinforcement pay-off racks, prestraightening part of vertical reinforcement, straightening traction part of horizontal reinforcement, and vertical reinforcement traction storage device, is introduced



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*Source: 7640504-2022-07-30.xml*