windgustfactor

[G] = windgustfactor(t, t0, CalcMethod, Iu, dispout)

Description

Convert wind velocity of duration t0 to t

Inputs

t

Wind averaging duration to convert to (e.g. Sustained Wind Duration) in (second)

Example: for 10-min wind averaging duration: t=600 (s)

t0=3600;

Wind averaging duration that data originally averaged at in (second)

Example: for 60-min wind averaging duration: t0=3600 (s)

If t0 is not defined, then t0 is considered as t0=3600 s

t0 can only have one element

CalcMethod=’cem’;

Wind gust factor calculation method

‘durst’: Durst (1960)

‘cem’: Coastal Engineering Manual, U.S. Army Corps of Engineers (2015)

‘cook’: Cook (1985) which is 3600 s gust factor based on Wieringa (1973) 600 s gust factor

‘krayer’: Krayer & Marshall (1992)

‘cem’ for t<=3600 s is similar to Dusrt (1960) relationship

‘cem’ for t>3600 s is Cook (1985) relationship with Iu=0.155

‘cook’ for Iu=0.175 is the commonly plotted curve

Iu=0;

Wind longitudinal turbulence intensity

dispout=’no’;

Define to display outputs or not (‘yes’: display, ‘no’: not display)

Outputs

G

Wind gust factor

G=U(t)/U(t0)

G=(wind velocity avereged over t seconds)/(wind velocity avereged over t0 seconds)

If t0=3600 s then G is calculated respect with 1-hour avereged wind velocity

If t0=3600 s then G=(wind velocity avereged over t seconds)/(wind velocity avereged over 3600 seconds)

If t0=3600 s then G=U(t)/U(3600)

Examples

t=600;
[G]=windgustfactor(t);

t(:,1)=[1:1:3600];
t0=3600;
[G]=windgustfactor(t,t0,'durst',0,'yes');

t(:,1)=[1:1:36000];
t0=3600;
[G]=windgustfactor(t,t0,'cem',0,'yes');

t(:,1)=[1:1:3600];
t0=3600;
[G]=windgustfactor(t,t0,'cook',0.175,'yes');

t(:,1)=[1:1:3600];
t0=3600;
[G]=windgustfactor(t,t0,'krayer',0,'yes');

References

American Society of Civil Engineers, ASCE-7. (2005). Minimum design loads for buildings and other structures (Vol. 7). Amer Society of Civil Engineers.

Cook, N. J. (1985). The designer’s guide to wind loading on building structures. Part I: Background, damage survey, wind data, and structural classification. Building Research Establishment, Watford. G_t_3600=1+0.42*Iu*log(3600/t);

Durst, C. S. (1960). Wind speeds over short periods of time. Meteor. Mag, 89(1056), 181-187. G_t_3600=0.977+(0.64/(1+(t/38.14)^0.685)); %from ASCE-7 (2005) G_t_3600=0.96+(0.648/(1+(t/38)^0.638)); %from Krayer and Marshall (1992)

Krayer, W. R., & Marshall, R. D. (1992). Gust factors applied to hurricane winds. Bulletin of the American Meteorological Society, 73(5), 613-618. G_t_3600=0.96+(0.839/(1+(t/36.27)^0.655));

U.S. Army Corps of Engineers (2015). Coastal Engineering Manual. Engineer Manual 1110-2-1100, Washington, D.C.: U.S. Army Corps of Engineers.

Wieringa, J. (1973). Gust factors over open water and built-up country. Boundary-Layer Meteorology, 3(4), 424-441. G_t_600=1+(1.42+0.3013*log((600/t)-4))*Iu;