C

where

K = a factor related to the surface roughness coefficient of the terrain K = 0.08 for exposure A K = 0.10 for exposure B K = 0.14 for exposure C

Figure 1.16. Background turbulence factor as a function of width and height of structure. (From NBCC 1995.)

CeH = exposure factor at the top of the building, H, evaluated using Fig. 1.15 B = background turbulence factor obtained from Fig. 1.16 as a function of building width-to-height ratio W/H H = height of the building W = width of windward face of the building

5 = size reduction factor obtained from Fig. 1.17 as a function of W/H and reduced frequency n0H/VH n0 = natural frequency of vibration, Hz VH = mean wind speed (m/s) at the top of structure, H

Figure 1.17. Size reduction factor as a function of width, height, and reduced frequency of structure. (From NBCC 1995.)
Figure 1.18. Gust energy ratio as a function of wave number. (From NBCC 1995).

F = gust energy ratio at the natural frequency of the structure obtained from

Fig. 1.18 as a function of wave number n0/VH 5 = critical damping ratio, with commonly used values of 0.01 for steel, 0.015 for composite, and 0.02 for cast-in place concrete buildings

Design Example: Calculations for Gust Effect Factor Cg. Given.

Fundamental frequency n0 = 0.125 Hz (period = 8 sec)

Critical damping ratio ยก = 0.010

Average density of the building = 195 kg/m3 (12.2 pcf)

Terrain for site = exposure B

Reference wind speed at 10 m, open terrain (exposure A) = 26.4 m/s (60 mph) Required. Gust factor Cg

Solution. From Fig. 1.15, for H = 240 m and exposure category B, exposure factor Cch = 2.17

Mean wind speed VH at top

Renewable Energy 101

Renewable Energy 101

Renewable energy is energy that is generated from sunlight, rain, tides, geothermal heat and wind. These sources are naturally and constantly replenished, which is why they are deemed as renewable. The usage of renewable energy sources is very important when considering the sustainability of the existing energy usage of the world. While there is currently an abundance of non-renewable energy sources, such as nuclear fuels, these energy sources are depleting. In addition to being a non-renewable supply, the non-renewable energy sources release emissions into the air, which has an adverse effect on the environment.

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