Key Analysis of Steel Frame Structure Detection, Identification, and Reinforcement Design
Introduction:During the construction process, it is essential to test the safety of the main structure and conduct specialized identification work. In the process of detection and identification, it is also necessary to carry out reinforcement work on the structure. Compared with traditional concrete structures, steel structures have unique advantages, including lightweight, fast assembly speed, large span, good seismic resistance, aesthetic appearance, reusability, and environmental friendliness. They are hailed as a new type of green building and are increasingly used in modern construction projects, gaining higher recognition within the industry. This area will also be a key focus for national support and development in the future.
The quality of housing construction not only significantly impacts the safety of residents’ lives and property but also relates to the development of society in China. Currently, construction enterprises have introduced more advanced technologies, materials, and equipment into construction projects; however, the probability of quality issues occurring during actual construction remains relatively high, drawing widespread attention from all sectors of society. To ensure that construction projects meet usage requirements, quality detection of the main structure is necessary to effectively enhance the safety and stability of the main structure. This article analyzes and discusses the detection, identification, and reinforcement of housing structures.
1Non-Destructive Testing Methods for Welds in Steel Structure Engineering
Steel structure engineering has gradually penetrated various construction fields, such as super-tall buildings, large sports venues, and long-span bridges. Behind this, the problems associated with steel structure engineering are increasingly attracting attention, especially the numerous welded joints present during steel structure assembly. To ensure that issues with welded joints are identified without damaging the structure, non-destructive testing methods must be employed. Non-destructive testing refers to the inspection of components or structures without causing damage. Different industries have their own non-destructive testing requirements for steel structure engineering. The GB50205-2020 Steel Structure Engineering Construction Quality Acceptance Standard, published by the Ministry of Construction, mentions non-destructive testing methods for welds, including ultrasonic testing, radiographic testing, and visual inspection. The JTG/T3650-2020 Highway Bridge Construction Technical Specification, published by the Ministry of Transport, includes non-destructive testing methods for welds such as ultrasonic testing, radiographic testing, magnetic particle testing, and visual inspection. The Q/CR9211-2015 Railway Steel Bridge Manufacturing Specification, published by China Railway Corporation, specifies non-destructive testing methods for welds, including ultrasonic testing, radiographic testing, magnetic particle testing, and visual inspection..
2Detection and Identification of Steel Frame Structures
2.1Detection of Masonry Mortar
The quality detection of building mortar is an essential part of the main structure detection. Common detection methods include the rebound method and the ultrasonic rebound comprehensive method. The rebound method involves applying momentum to the main structure and using a hammering method to test the quality of the mortar. Due to external vibrations, the mortar in the building can only absorb some energy, with a certain distance between the interior and surface of the building. The ultrasonic rebound comprehensive method combines the principles of the rebound method and ultrasonic technology to conduct quality testing, helping workers identify quality issues that are difficult to detect with the naked eye.
2.2Precise Location of Weld Defects in Steel Structure Engineering
In the non-destructive testing of welds in steel structure engineering, it is crucial to ensure precise defect localization. First, it is necessary to select suitable non-destructive testing techniques for the welds and clearly identify defect locations. Relevant equipment can be used to comprehensively scan the testing materials and locations, controlling the speed of detection and scanning to accurately reflect on the display screen, helping workers understand various defects present in the steel structure engineering. This allows for clear comparisons of defect locations across multiple tests. If a defect signal is found near the signals from the previous two tests, it can be determined that the defect is located on the surface of the weld. If the signal is between two waves, it indicates that it is in the middle of the weld. If the defect signal obtained during testing is adjacent to the previous defect, it can be concluded that the defect is located at the root of the weld.
2.3Appearance and Dimension Detection
During the quality detection of the main structure, the primary focus is on the building’s appearance and dimensions, including common components like reinforced concrete. At this stage, it is necessary to check for any quality issues in the building, ensuring that the verticality, cross-sectional dimensions, and flatness of the components meet the specifications. Furthermore, reasonable detection measures should be selected, as the concrete components of the main structure are more susceptible to external environmental influences, necessitating annotations in the detection report.
2.4Reasonable Assessment of Weld Quality in Steel Structure Engineering
When applying non-destructive testing techniques for welds in steel structure engineering, multiple testing techniques should be comprehensively utilized, conducting thorough inspections of the weld components and connections involved in the steel structure engineering. This allows for the assessment of whether the actual quality of the welds meets standards. It is worth noting that when using non-destructive testing techniques, the thickness of the steel plates used in construction should be greater than 8mm, as the use of ultrasonic and other technologies can yield better detection results, further ensuring the overall quality level of the steel structure engineering. Immediate detection and identification of defects in the welds help determine quality. Additionally, when testing steel structure components, if two defects are found within a distance of less than 4mm, the operators need to re-test and recalculate to ensure the overall quality level of the steel structure engineering.
2.5Detection of Reinforcement Performance
During the construction of the main structure of a building, reinforcement is a common material. In the research and analysis of reinforcement detection, it is crucial to assess whether the actual performance meets the standard requirements for the main structure. After the reinforcement is transported to the construction site, its mechanical properties need to be tested. Since construction projects vary, the scales and techniques used also differ significantly, leading to different requirements for reinforcement usage. Construction enterprises need to conduct sampling inspections of reinforcement samples based on the actual situation on-site, which helps reduce workload and enhance detection levels. This includes not only mechanical testing measures but also the use of reinforcement welding processing techniques. During welding work, there are high standards required for relevant technical personnel, and quality issues can easily arise during the construction period. If such issues are detected during testing, immediate measures should be taken to address them, preventing exacerbation and ensuring overall quality safety.
2.6Detection of Reinforcement Position, Quantity, and Protection Layer Thickness
In reinforced concrete building structures, the quality of the project is influenced by the quantity and distribution of reinforcement. Therefore, to control the quality of the main structure, attention must be paid to the quality and quantity of reinforcement. Many factors affect the durability of the main structure, with reinforcement quantity and protection layer thickness being significant factors. Reinforcement plays a crucial role in concrete structures, and a certain thickness of the protection layer can provide a barrier and protection for the reinforcement. Thus, controlling the quantity and distribution of reinforcement and the thickness of the protection layer is vital for the safety and durability of the structure. Therefore, during on-site detection of the main structure, strict adherence to specifications is necessary to control the internal quantity of reinforcement and the thickness of the protection layer. The electromagnetic induction method for detecting the position, quantity, and thickness of the reinforcement protection layer is based on electromagnetic field theory. In essence, reinforcement acts as an electric dipole, effectively receiving external electric fields. When the coil, acting as a strict magnetic dipole, provides alternating current to the signal source, it emits an electromagnetic field. Under numerous factors, the output voltage of the coil exhibits significant changes. When detecting reinforcement, the position of the reinforcement and the thickness of the protection layer can be determined by voltage fluctuations.
2.7Reasonable Assessment of Weld Quality Levels in Steel Structure Engineering
When applying non-destructive testing techniques for welds in steel structure engineering, it is necessary to comprehensively utilize multiple testing techniques and conduct thorough inspections of the weld components and connections involved in the steel structure engineering. This allows for the assessment of whether the actual quality of the welds meets standards. It is worth noting that when using non-destructive testing techniques, the thickness of the steel plates used in construction should be greater than 8mm, as the use of ultrasonic and other technologies can yield better detection results, further ensuring the overall quality level of the steel structure engineering. Immediate detection and identification of defects in the welds help determine quality. Additionally, when testing steel structure components, if two defects are found within a distance of less than 4mm, the operators need to re-test and recalculate to ensure the overall quality level of the steel structure engineering.
3Reinforcement Measures for the Main Structure
The rationality of the reinforcement scheme design for steel frame structures must clarify the basic principles before design, which mainly include: (1) When calculating loads, it must be based on the actual stress conditions of the structure, including measured inspections and sampling tests; (2) The structural function must be verified through engineering practice, and the reinforcement scheme must be superior to the calculation results; (3) During the reinforcement process, it is necessary to assess the stress conditions of both the original structure and the new structure. In the reinforcement of the steel frame structure for this commercial supporting building, the connection methods and node design are two important aspects. When increasing the component cross-section and replacing existing components, the rationality of the connection methods must be fully considered, placing the connection methods of various nodes of the steel frame structure at the forefront of the reinforcement scheme. Currently, most steel frame structures mainly adopt three connection methods: bolted connections, riveted connections, and welded connections. The steel frame structure of this commercial supporting building primarily uses welded connections, so the reinforcement treatment should focus on the welding reinforcement aspect.
3.1Strengthening Quality Supervision in Design Drawings
Managers must pay attention to quality inspections. When supervising and briefing work, it is necessary to promptly inform different departments about the importance and severity of deepening design, strictly implementing the engineering review system. Drawings without qualifying standards must not be used as a basis for construction.
3.2Enclosure Structure Subsystem
(1) Load-bearing enclosure structure load-bearing function rating. The load-bearing maintenance system of this factory mainly consists of roof purlins and roof panels. Based on the load-bearing function rating results of the enclosure structure of this factory, according to GB50144-2019 “Reliability Assessment Standard for Industrial Buildings,” section 7.4, the safety level of the load-bearing enclosure structure under normal use conditions is rated as Class A. (2) Non-load-bearing enclosure structure connection rating. The non-load-bearing enclosure system of this factory mainly consists of exterior walls. After on-site investigation, no abnormalities were found in the component connections, and they generally meet the requirements. According to GB50144-2019 “Reliability Assessment Standard for Industrial Buildings,” section 7.4, the connection of the non-load-bearing enclosure structure under normal use conditions is rated as Class A.
3.3Establishing a Quality Supervision Management Mechanism under New Conditions
In the prefabricated light steel construction industry, the design and production departments influence the overall project quality. This means that the supervision work of the construction administrative authority must include both production and construction aspects, ensuring effective supervision in both areas. The supervising unit must establish strict review standards and supervision plans. In line with the requirements of prefabricated structures, the frequency of supervision, inspection elements, acceptance of important materials and products, etc., should be improved. Supervisors must thoroughly understand the characteristics and issues of the projects they are responsible for, proactively addressing key areas and potential problems. For instance, the design department should conduct briefings based on the overall characteristics of the project, further improve prefabricated components, effectively integrate construction drawings from different specialties, enhance control over raw material quality during production, check component quality, control processes at critical locations, and check structural performance at key locations. By notifying different responsible departments of potential issues in advance, work can be more efficient and targeted measures can be taken. Improve supervision over various manufacturers and responsible parties involved in construction. Manufacturers must have complete facilities to ensure quality checks, suitable monitoring plans, and quality inspection systems, and improve responsibility systems and material testing processes, starting from internal checks during self-inspection handovers.
3.4Seismic Performance-Based Design
In recent years, performance-based seismic design has become a fundamental method for addressing seismic design issues in the engineering field. The basic idea of performance-based seismic design is to achieve “high ductility, low elastic bearing capacity” or “low ductility, high elastic bearing capacity.” By increasing bearing capacity, the onset of plastic working in the structure can be delayed, reducing plastic deformation and relaxing the limits on the width-to-thickness ratio of components. Article 9.2.14 of the “Building Seismic Design Code” specifies the width-to-thickness ratio limits for Class A, B, and C components in single-story steel structure factories with light roofs, which is a simplified approach to performance-based seismic design and is easy to apply. Through comparative calculations, it is evident that the economic viability of different performance-based design approaches varies under different basic seismic accelerations and wind pressures. For single-story steel structure factories with light roofs, wind load is a significant factor affecting the steel frame’s steel consumption. When the basic wind pressure is not less than 0.60kN/m2, the steel frame calculations are controlled by horizontal displacement, making the impact of basic wind pressure on steel consumption more pronounced. In areas where the basic seismic acceleration does not exceed 0.20g, adopting a low ductility, high elastic bearing capacity performance-based design approach results in lower steel consumption for the steel frame.
3.5Key Points in Structural Measures Design
In the design of structural measures, a comprehensive approach should be taken, considering the effects of temperature shrinkage. Additionally, the pouring time in structural measures must be greater than >60d, and the impact of concrete shrinkage and temperature changes, as well as reinforcement temperature changes on the surface and bottom reinforcement, must be considered. Furthermore, for irregularly shaped floors in civil buildings, additional reinforcement should be added at corners, protrusions, and concave angles. The design of reinforcement and expansion joints at both ends of civil buildings must strictly adhere to regulations.
3.6Reasonable and Scientific Plane Layout
To ensure the overall structural stability of the steel frame structure, a scientifically reasonable plane layout is required. In the design process of this project, the overall regularity of the building was prioritized, considering the regularity of the plane, elevation, and section layouts, which is significant for ensuring good seismic performance of the steel frame. Secondly, a reasonable structural layout scheme was selected based on the plane layout and combination methods, while fully considering material strength and component cross-section size requirements. Thirdly, the impact of natural factors on structural seismic performance was assessed in advance, and corresponding measures were taken. The detailed plane layout scheme for steel beams in this project features main beams with a span of 8m in the X direction and 15.8m in the Y direction. The Y-direction steel beams are designed with flared ends to meet the negative bending moment requirements at the ends of the beams while ensuring that the height of the middle section of the beams meets the specifications, thus ensuring the safety of the steel beams. Secondary beams are arranged unidirectionally, with a spacing of 2.7m.
3.7Design for Ensuring Building Structure Safety
Currently, the structural design system for civil buildings in China is still not complete, leading to unreasonable civil designs and deficiencies in seismic design. To ensure the safety of civil buildings, the structural design must be made more rational. In structural design, the appropriate structure type should be selected. For instance, steel structures, which are currently more frequently used, have many advantages compared to reinforced concrete structures, such as being lightweight, high strength, and shorter construction periods. These features meet the requirements for civil building structural design, and the larger spatial arrangement of steel structures allows for more flexible civil building designs, which is very convenient for owners and construction personnel. Additionally, the use of steel structures can reduce the consumption of sand, gravel, cement, and other raw materials, lowering construction costs and, to some extent, reducing project costs, thus ensuring construction periods and project quality.
4Conclusion
As steel structure engineering becomes more widely applied, the variety of components will also increase, and the quality of welding connections between components will receive increased attention. Non-destructive testing, as a quality control measure, is crucial for ensuring quality, and it is essential for every non-destructive testing personnel in steel structures to reflect and ponder this. Relevant testing personnel should deeply understand the characteristics of housing structures, effectively reinforce weak areas of the structure, and enhance the safety and stability of the main structure. They should be adept at accumulating experience, learning advanced technologies, and improving their professional abilities. This will ensure that the final testing data is more accurate and provide effective support for the sustainable development of the construction industry.