When Galvanized steel plates are selected for building structures, the mechanical performance parameters should be primarily based on the design load. For the main frame of high-rise buildings, it is recommended to use high-strength galvanized steel sheets with a yield strength of ≥345MPa, such as ASTM A653 SS Grade 340 or EN 10346 S350GD+Z. According to the load test data, in a beam structure with a span of 12 meters, the maximum deflection deviation of this type of material can be controlled within L/360 (L represents the span), and its wind pressure resistance capacity can reach 3.0 kN/m² (equivalent to 130% of a wind speed of 60m/s). In the giant support structure of the Shanghai Tower in China, the proportion of S550GD+Z grade galvanized sheets is 38%. After 2 million cycles of fatigue life tests, the strength attenuation rate is only 5.3%, far exceeding the 22.8% of ordinary carbon steel.
The corrosion protection grade directly determines the service life and economy. For coastal or industrial zone projects, hot-dip galvanized steel sheets with a zinc coating quality of ≥275g/m² (G90 standard) should be selected, and the median zinc coating thickness should be above 50μm. The case of the International Zinc Association shows that in highly corrosive environments with salt spray concentrations greater than 500mg/m³ (such as the steel structure of the Qingdao Cross-Sea Bridge), after 25 years of use, the residual zinc coating of Z275 galvanized sheets remains above 100g/m², with an average annual corrosion rate of less than 1.5μm. Compared with ungalvanized steel structures, the maintenance cycle is extended by 400%, and the total life cycle cost is reduced by 35%. The verification of the support structure of Kansai International Airport in Japan, which uses steel plates with a hot-dip galvanized coating of 275g/m², only requires one repair and maintenance in the Marine atmospheric environment over 30 years, which is far less than the five times required for epoxy coatings.
The geometric specifications need to be adapted to the manufacturing accuracy and construction efficiency. The main structure of the building is recommended to use standard plates with a thickness of 1.5-25.0mm and a width of 1500-2500mm. The thickness tolerance should be controlled within ±0.08mm (in accordance with EN 10143 standard). In the third runway project of Hong Kong International Airport, after the adoption of galvanized steel plates with a tolerance of ±0.05mm, the assembly gap of components was compressed from the conventional 1.2mm to 0.3mm, the matching accuracy of bolt holes was improved by 90%, and the installation speed was increased by 45%. For purlin components that require cold-bending forming, it is necessary to ensure that the elongation of the galvanized sheet is ≥16% (refer to the GB/T 2518 standard). The measured success rate of cold-bending 180° of Baosteel Q345GJZ steel grade without cracking is 99.7%, and the failure rate is 60% lower than that of traditional steel plates.
Certification compliance and traceability are crucial for risk control. It is necessary to verify whether the supplier has passed the ISO 1461 certification and has a complete smelting composition report (carbon content ≤0.25%, silicon content fluctuation <0.03%). In 2018, a high-rise apartment building in Melbourne was hit by a quality claim worth 500 million US dollars due to the use of uncertified galvanized sheets (with silicon content exceeding the standard by 0.18%), which led to a 47% decline in the adhesion of the zinc coating. Experiments conducted by authoritative institutions show that the qualified rate of Galvanized steel plate samples in compliance with ASTM A123 with a red rust area of ≤5% after 4,800 hours of salt spray testing is 98.2%, which is much better than the 76.5% of non-standard products. The construction party should request the manufacturer to provide a report on the uniformity of the coating for each batch of materials (double-sided difference <15%) to eliminate the risk of electrolytic corrosion caused by excessive symmetry deviation.
Terminal decision-making should integrate engineering tests and empirical cases. Simulation by the BRE Research Institute in the UK confirmed that in a typical environment with a humidity of 70%RH, within 30 years of contact between the S320GD+Z plate conforming to BS EN 10346 and the concrete, the effective coverage radius of cathodic protection reached 1.2 meters, and the probability of steel bar corrosion decreased from 17.3% to 2.1%. In the Burj Khalifa project in the United Arab Emirates, 2.5mm thick Z275 galvanized steel plates were selected to make the curtain wall keel. Under a high-temperature environment of 55℃, the measured linear expansion coefficient was stable at 11.7×10⁻⁶/℃, and the thermal deformation difference with the glass curtain wall was controlled within the safety threshold of 0.15mm/m. The comprehensive cost model shows that although the initial cost of purchasing galvanized steel sheets that meet international standards increases by 18%, the total project budget can be optimized by 12% to 15% by reducing quality disputes by 75% and cutting the frequency of inspection and rework by 90%.