Dapeng Town Industrial Park, Tongshan District, Xuzhou City, Jiangsu Province, China
Complex working condition calculation problem: The mesh frame steel structure is subject to complex forces, and the design needs to consider wind, snow, earthquake and other loads, self-weight, temperature stress and so on. Although the existing design software keeps improving, the calculation still has errors under special working conditions and complex structures. Such as large span, shaped frame in the strong wind and seismic coupling, accurate simulation and calculation of its force response is quite a challenge, easy to lead to the design of unreasonable safety reserves.
Node design to be optimised: Nodes are related to the overall performance of the structure. Welded ball and bolted ball nodes have their own advantages and disadvantages. Welded ball node welding quality affects the strength and stability, improper treatment of the weld is easy to stress concentration; bolt ball nodes require high bolt accuracy and installation, loose bolts or poorly designed ball diameter will weaken the performance of the node. How to optimise the node form and parameters for different engineering needs is the key to design.
Dilemma of steel quality control: steel is the basic material of net frame, and its quality determines the safety and life of the structure. The quality of steel in the current market varies, and the chemical composition and mechanical properties of some products do not meet the national standards. Inferior quality steel used in net frame is easy to cause safety accidents, while the supervision of steel quality source and circulation link is more difficult, need to establish a more stringent quality control system and traceability mechanism.
Application of new materials lagging behind: although new materials continue to emerge, but applicable to the net frame and cost-effective material research and development and application of slow. For example, high strength, high toughness and good weather resistance of steel or composite materials, due to high cost, complex processing technology, etc., in the network frame application is limited. R & D promotion of such materials to enhance the performance of network frame, reduce costs is significant.
Installation precision is difficult to ensure: the net frame installation precision requirements are high, the length of the rod, angle and node position deviation affects the structural stress and stability. During construction, measurement errors, component processing deviations and improper installation order will cumulatively lead to the overall accuracy out of control. For example, when large-scale net frame is installed at high altitude, it is difficult to correct the deviation quickly due to the lack of efficient and accurate measurement means and fine-tuning mechanism.
Unstable welding quality: Welding is a key construction link. Improper selection of welding process parameters, differences in welders’ skills and environmental factors will make the welding quality fluctuate. The weld appears porosity, slag, not welded through and other defects, reducing the node strength and structural integrity. To ensure the quality of welding, it is necessary to standardise the welding process, strengthen the training of welders and improve the monitoring of the construction environment.
Fire performance to be improved: steel fire resistance is poor, high temperature strength and stiffness drop sharply. The net frame is easy to collapse in the fire, threatening the safety of life and property. Traditional fire coatings have poor durability, thickness, affecting the aesthetics and other issues, new and efficient fireproofing materials and structures R & D and application promotion is urgent.
Anti-corrosion measures need to be upgraded: long-term exposure to corrosion, affecting the appearance and life. Existing anti-corrosion coating life is limited, regular maintenance and recoating is required, which increases the cost. Research and development of long-lasting anti-corrosion coating or the use of new anti-corrosion technology, such as hot-dip zinc-aluminium alloy, metal composite coatings, etc., which can extend the anticorrosive cycle of the network frame, reduce maintenance costs.
Limitations of health monitoring technology: in use, the net frame will be affected by a variety of factors will produce damage and deformation. Existing structural health monitoring system in the sensor accuracy, durability and data processing algorithms and other aspects of deficiencies. For example, the long-term stability of the sensor is poor, it is difficult to accurately capture the small damage signals, and the data analysis method can not identify the early structural damage and early warning in a timely and effective manner.
Sloppy maintenance management: lack of perfect maintenance management system and professional team. Regular inspections and maintenance plans are poorly implemented, and repairs are mostly emergency treatments after the fact, with a lack of preventive maintenance strategies and systematic repair programmes. This leads to the accumulation of small problems into big hidden dangers, shortening the service life of the network frame, increasing maintenance costs and safety risks.
