IEC 60826:2017 occupies a middle ground. Its reference wind (V_R) is defined as a 10-minute average at 10 m height, and the combination factor already incorporates terrain roughness. In the same coastal case the IEC panel method yielded intermediate results, closer to the Chinese values once the basic wind speed was adjusted to the corresponding reliability class. The methodological contrast is clear. Chinese practice still relies on the extreme-value Type I distribution and voltage-dependent return periods (30 years for 110–330 kV, 50 years for 500–750 kV). ASCE 74 treats the 100-year MRI as the default and includes explicit appendices for downburst and tornado loads-phenomena that Chinese standards address mainly through regional amplification factors.
These numerical gaps feed directly into steel selection. Higher peak forces require matching both thickness and strength. On the two Guangdong projects I examined, increasing the design wind by 12–15 % pushed several critical leg members from 12 mm Q345 angles to 14 mm or to Q420 in the most heavily loaded panels. The same adjustment in the Sichuan mountain site, where local topography amplifies yawed winds, forced additional bracing thickness to keep buckling ratios within limits. Using hot-dip galvanized structural steel of the correct grade and section ensures the galvanized coating remains intact after fabrication while delivering the required yield strength under the governing load combination.
The most common pitfalls that lead to wind-induced collapse lie less in the codes themselves than in how they are applied. Relying on a single "governing" wind direction taken from flat-terrain maps underestimates shear in complex topography; both DL/T 5551 and ASCE 74 require checks at 0°, 45°/60° and 90°, yet the force-coefficient tables still rest on solidity-ratio curves from 1970s wind-tunnel work. Insufficient allowance for local directional spectra, or under-estimating the effect of conductor drag under yawed flow, can leave the structure with inadequate reserve. Side-by-side recalculations of the three recent projects (two coastal, one mountainous) using the published formulas in DL/T 5551-2018 Chapter 6, ASCE MOP 74 Chapters 2–3 and IEC 60826 Annex B confirmed that conservative envelopes add steel without always adding proportional safety unless site-specific data are introduced.
When thickness, grade and coating are matched to the actual wind regime derived from the governing code, the risk of progressive collapse under extreme events drops sharply. For projects facing multi-code compliance or typhoon-prone corridors, we supply high-strength galvanized steel with full mill certificates and coating documentation aligned to the selected design standard. Contact us to review member schedules against your wind-load envelope.
