QX/T 438-2018 in English

Analysis of the Standard's Core Content

This standard systematically specifies a methodology for calculating bridge design wind speeds, focusing on three key technical modules: reference meteorological station selection, wind speed sequence correction, and extreme value probability analysis. It applies to the entire standardized process of bridge wind-resistant design demonstration.

Key Technical Points

1. Reference Meteorological Station Selection Criteria

Reference stations must meet three core criteria: at least 30 years of observation data, terrain similarity, and environmental stability. Specifically, the correlation with the strong wind samples from the bridge-site meteorological station must pass a 0.05 confidence level test.

2. Wind speed sequence consistency correction

Includes four methods: time interval correction, height correction, station relocation correction, and environmental change correction, among which:

• Time interval correction: A linear regression equation needs to be established for 2min→10min
• Altitude correction:Use the power exponential formula in Appendix B$$ \alpha=\frac{\lg(v_2/v_1)}{\lg(z_2/z_1)} $$

3. Calculation of bridge design wind speed

Core steps:

1. Use extreme value type I distribution to calculate the 100-year return period wind speed$$ X_T=u-\frac{1}{a}\ln[-\ln(1-\frac{1}{T})] $$
2. Apply correction factors based on the surface type of the bridge site (see Table A.1)
3. Special terrain requires a bridge site meteorological station for correlation analysis

Recommendations for standard implementation

1. Data quality control

It is recommended to implement the following on the reference station data:

• Completeness check (missing measurement rate ≤ 5%)
• Homogeneity test (using the t-test method in Appendix C)
• Extreme value review (combined with historical weather processes)

2. Complex Terrain Processing

For special terrains such as canyons and mountains:

• Additional wind profiler radar observations should be made
• CFD numerical simulation should be used for auxiliary correction
• An observation period of ≥ 3 years is recommended

3. Engineering Application Tips

Note for long-span bridges:

• The wind speed at the height of the main beam needs to be calculated according to the wind profile
• Three-dimensional wind field effects should be considered
• Wind tunnel testing is recommended