Portal steel frame structures are widely used in industrial plants, warehousing and logistics due to their advantages such as light weight, short construction period, and high space utilization. However, long-term exposure to the natural environment and operational loads makes them susceptible to structural damage due to material aging, external impacts, or design flaws. If not detected and addressed promptly, this can threaten overall stability. Therefore, scientific and systematic damage detection and targeted repair are crucial for ensuring their safety.
Damage detection of portal steel frame structures needs to be conducted from both macroscopic deformation and microscopic defects perspectives. At the macroscopic level, the straightness, verticality, and node connection status of components need to be carefully examined. For example, column tilting may be caused by foundation settlement or lateral loads, requiring measurement of verticality deviation using a total station; beam deflection may be caused by long-term overloading or insufficient stiffness, requiring measurement of deflection values using a level or laser displacement gauge. At the microscopic level, specialized equipment is needed to detect hidden damage. For example, ultrasonic flaw detectors can be used to check for defects such as porosity and slag inclusions inside welds, while magnetic particle or penetrant testing can be used to detect surface cracks. Simultaneously, a Leeb hardness tester can be used to assess the strength degradation of the steel. Furthermore, corrosion is the most common form of damage to portal steel frame structures, requiring regular monitoring of coating thickness and steel cross-sectional loss rates at critical locations using thickness gauges.
Differentiated treatment strategies must be adopted based on the type of damage detected. For weld defects, if the crack depth does not exceed a certain proportion of the wall thickness and does not penetrate the cross-section, the crack can be removed using carbon arc gouging, followed by re-welding according to the original process. If the crack has significantly reduced the load-bearing capacity, stiffening plates or high-strength bolts should be added for reinforcement. When a component suffers localized corrosion or hole damage, if the remaining cross-section still meets the load-bearing requirements, the corroded area can be ground down, reinforced with steel plates of the same material, and welded in place. If corrosion has severely weakened the cross-section, the damaged component must be cut and replaced. For loose connections or missing rivets, bolts must be tightened, rivets replaced, or high-strength bolts replaced. Simultaneously, gaps between connecting plates should be checked, and structural adhesive should be used for sealing if necessary.
Repairing damage to portal steel frame structures requires consideration of both structural safety and construction feasibility. A specific plan must be developed before repair, clearly defining the reinforcement scope, process flow, and quality control standards. For example, when using carbon fiber reinforcement, it is essential to ensure a smooth base layer, that the fiber cloth is laid in the same direction as the stress direction, and to control the thickness and overlap length of each layer. When adding a support system, the compatibility between the new component and the original structure must be verified to avoid localized stress concentration. During the repair process, critical procedures should be strictly monitored. For example, welding operations require control of preheating and interlayer temperatures to prevent cold cracking; high-strength bolt connections must be completed in two stages, initial tightening and final tightening, to ensure the torque values meet design requirements.
Damage prevention for portal steel frame structures requires continuous management throughout their entire lifecycle. During the design phase, load combinations, environmental effects, and construction deviations should be fully considered to reasonably determine the structural safety margin. During construction, quality control must be strengthened to ensure that welding quality, bolt tightening force, and coating thickness meet specifications. During the service phase, a regular inspection system should be established, focusing on monitoring corrosion-prone areas, high-stress zones, and deformation-sensitive components, while avoiding unauthorized changes to the structural purpose or overloading. Furthermore, for corrosive environments such as coastal areas and chemical plants, weathering steel or additional anti-corrosion coatings should be used, and surface contaminants should be cleaned regularly to slow down the corrosion process.
Damage detection and treatment of portal steel frame structures is a systematic project, requiring scientific testing as a prerequisite, precise repair as the core, and full-cycle management as a guarantee. Through regular inspections, professional assessments, and timely intervention, the development of structural damage can be effectively controlled, extending the service life of portal steel frame structures and providing solid support for the safe operation of industrial buildings.
