Embedded parts, curtain wall accessories, are key components connecting the curtain wall to the main structure. Their anchoring performance directly impacts the safety and durability of the curtain wall system. Under freeze-thaw cycles, embedded parts are subject to repeated temperature stress, moisture penetration, and concrete expansion and contraction, which can easily lead to anchor failure. To prevent these problems, a comprehensive protection system must be established, encompassing material selection, design optimization, construction control, and maintenance management.
Material selection is fundamental to ensuring the frost resistance of embedded parts. Q235B steel should be preferred for anchor plates, as its strength and toughness can withstand the stress fluctuations of freeze-thaw cycles. Anchor bars should use Grade II deformed steel to avoid fracture due to the brittleness of cold-rolled steel. The choice of anchoring adhesive is particularly critical. Chemical anchor adhesives must be resistant to low temperatures and freeze-thaw cycles to prevent bond strength degradation at low temperatures. Some imported modified epoxy resin adhesives have passed laboratory freeze-thaw cycle testing and can meet long-term operating requirements in temperatures ranging from -18°C to 5°C. Furthermore, hot-dip galvanizing forms a dense oxide film that effectively blocks moisture and chloride ion corrosion, extending the service life of embedded parts. During the design phase, meticulous calculations are required to ensure anchorage capacity. The design of embedded parts must account for combined tensile, shear, and bending stresses. The anchor bar diameter and length must be determined using formulas to ensure that the design tensile stress is lower than the standard tensile strength of the steel bars. The anchor plate thickness and anchor bar spacing must meet structural requirements to avoid localized stress concentrations. In freeze-thaw-sensitive areas, the number of anchor bars can be increased or slotted embedded parts can be used to distribute the load and reduce the load on individual anchor bars. Furthermore, the design must allow for adjustment, such as slotted holes in support connectors to allow for three-dimensional fine-tuning to compensate for structural deformation caused by freeze-thaw.
Quality control during construction is crucial for preventing anchorage failure. Before installing embedded parts, the main structural dimensions must be verified. Any deviations must be adjusted promptly to prevent displacement of the embedded parts due to civil engineering errors. Plug welding or T-welding should be used to weld the anchor bars to the anchor plate. The weld grade must be determined through calculation, and certified welders must be employed to ensure full, defect-free welds. Anchor bolt holes must be drilled away from main reinforcement, and the hole diameter and depth must comply with regulations. After drilling, remove dust and keep the holes dry to prevent moisture retention and accelerated freeze-thaw damage. During concrete pouring, control the vibration force to prevent displacement of embedded parts. Cover with insulation material after pouring to prevent premature freezing.
Post-installation anchoring must strictly adhere to pull-out test requirements. Before installation, chemical anchors must undergo on-site individual pull-out testing. No noticeable slippage is observed at a load of 1.5 times the design value. Test results must be verified against design calculations, and the design bearing capacity must not exceed 50% of the ultimate bearing capacity. In low-temperature environments, cryogenically resistant chemical hoses are required. No special insulation measures are required during installation, but the drilled holes must be dry and free of ice crystals. Expansion bolts have limited application in freeze-thaw zones, as their bearing capacity stability is lower than that of chemical anchors. Caution should be exercised when edges are subjected to shear or combined shear and tension loads.
Maintenance and management are key to extending the service life of embedded parts. Regular inspections should focus on anchor plate corrosion, weld cracking, and loose anchors. If the galvanized coating is damaged, reapply anti-rust paint promptly. In areas subject to frequent freeze-thaw cycles, inspections can be increased, and local reinforcement can be performed as necessary. For curtain wall renovation projects in existing buildings, the load-bearing capacity of embedded parts should be reassessed. If these do not meet the requirements, reinforced steel plates should be welded or chemical anchors should be added to ensure connection reliability.
Through optimized materials, design, strict construction control, and thorough maintenance, embedded parts of curtain wall components can achieve long-term, stable anchoring under freeze-thaw cycles. This comprehensive protection system not only enhances the safety of the curtain wall system but also reduces maintenance costs throughout its lifecycle, providing technical support for the reliable operation of building curtain walls in extreme climates.
