1. Lifetime of buildings Churches: 500years Harbor facilities: 200 years Family houses: 100 years Road bridges: 100 years Railway bridges: 80 years Shopping malls: 80 years Office buildings: 50 years Industrial buildings: 40 years What is the max, windspeed which is expected to occur once in the lifetime of the building?

4. Prediction of design wind speeds Return Period (mean recurrence interval) : Unit : depends on population from which extreme value is selected A 50-year return-period wind speed has an probability of exceedence of 0.02 in any one year Return Period, R = e.g. for annual maximum wind speeds, R is in years it should not be interpreted as occurring regularly every 50 years or average rate of exceedence of 1 in 50 years Wind loading and structural response Lecture 4 Dr. J.D. Holmes

5. Prediction of design wind speeds Lifetime of structure, L Appropriate return period, R, for a given risk of exceedence, r, during a lifetime ? Assume each year is independent Probability of non exceedence of a given wind speed in any one year = Probability of non exceedence of a given wind speed in L years = Risk of exceedence of a given wind speed in L years,

6. Prediction of design wind speeds Example : L = 50 years R = 50 years There is a 64% chance that U 50 will be exceeded in the next 50 years Risk of exceedence of a 50-year return period wind speed in 50 years,

7. MRIpeak gust wind speed yearsconversion factor 50.78 100.84 250.93 501 1001.07 2001.14 5001.23

9. Ceppi, P., Della-Marta, P.M., Appenzeller, C.: 2008, Extreme Value Analysis of Wind Speed Observations over Switzerland, Arbeitsberichte der MeteoSchweiz, 219, 43pp

12. T = 4 - 4.5 s link

13. William Jacobs: Building Periods: moving forward (and backward) STRUCTURE magazine June 2008