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Table 2. Comparison of design velocity pressures between ASCE 7-10
<br />Exposure D and ASCE 7-05 Exposure C
<br />Location
<br />Boston, MA
<br />Risk
<br />Category,
<br />11
<br />ASCE 7-10'
<br />ASCE, 7-052
<br />Design
<br />Wind
<br />Speed
<br />(MPH)
<br />128
<br />ASD
<br />Velocity
<br />Pressure'
<br />(so
<br />25,2
<br />LRFD
<br />Velocity
<br />Pressure'
<br />(psf)
<br />42.1
<br />Design
<br />Wind
<br />Speed
<br />(MPH)
<br />1.05
<br />ASD
<br />Velocity
<br />PrcssLjre2
<br />_ (Usf)
<br />24.0
<br />LRFD
<br />Velocity
<br />Pressure 2
<br />(psf)
<br />38.4
<br />VA Beach, VA
<br />11
<br />122
<br />22.9
<br />38,2
<br />114
<br />28.3
<br />45.2
<br />Miami, FL
<br />11
<br />170
<br />44.5
<br />74,2
<br />146
<br />46.4
<br />74,2
<br />Galveston, TX
<br />Boston, MA
<br />11
<br />III, IV
<br />ISO
<br />140
<br />343
<br />30.2
<br />57.8
<br />50.3
<br />132
<br />105
<br />37.9
<br />27.6
<br />60.7
<br />44.1
<br />VA Beach, VA
<br />111, IV
<br />132
<br />26.8
<br />44,7
<br />114
<br />32.5
<br />52.0
<br />Miami, Fl,
<br />III, IV
<br />181
<br />50.5
<br />84.4
<br />146
<br />53.3
<br />853
<br />Galveston, TX I
<br />III, IV
<br />160
<br />39.4
<br />65.7 ,
<br />132
<br />43.6
<br />69.8
<br />' Exposure D at 33'mean roof height, K� = 1.18.
<br />2 Exposure C at 33'mcan roof height, K, = 1.0.
<br />Wind Load Factors
<br />The ratio of ASD to LRFD design wind pressures in Tables I and 2 is constant as would be
<br />expected based on the applicable equations, A slight reduction in. ASD pressures relative to
<br />1, FD pressures results from the load factor differences between ASCE 7-10 and ASCE 7-05 (i.e,
<br />ratio of 0.6 Vel-SLIS 0.625 where 0.6 = 0.6/1.0 and 0.625 = 1/1.6). The precise value of tile
<br />reduction in ASD load relative to LLD load between ASCE 7-10 and ASCE 7-05 due to load
<br />factor changes alone is 0.6,/0.625 = 0.96 or 4 percent,
<br />Table 3. Comparison of LRFD design velocity pressures based on ASCE 7-10
<br />and ASCE 7-05
<br />Location
<br />Boston, MA
<br />Risk
<br />Category,
<br />11
<br />ASCE 710
<br />ASCE
<br />7-05
<br />Ratio
<br />Design
<br />Wind
<br />Speed
<br />(MPH)
<br />128
<br />[A]
<br />Exp C
<br />Velocity
<br />preSS111.02
<br />(Psf)
<br />35.7
<br />[B]
<br />Exp D
<br />Velocity
<br />Presstire➢
<br />(pst)
<br />42.1
<br />Design
<br />Wind
<br />Speed
<br />(MPH).
<br />105
<br />[C]
<br />Exp C
<br />Velocity
<br />Pressure,
<br />(psf)
<br />38.4
<br />[C]
<br />0.93
<br />fB]
<br />[C]
<br />IJO
<br />VA Beach, VA
<br />11
<br />122
<br />32.4
<br />38.2
<br />114
<br />45.2
<br />0.72
<br />0,84
<br />Miami, FL
<br />11
<br />170
<br />619
<br />74.2
<br />146
<br />74.2
<br />0.85
<br />1.00
<br />Galveston, TX
<br />11
<br />150
<br />49.0
<br />57.8
<br />132
<br />%7
<br />0.81
<br />0.95
<br />Dallas, TX
<br />Boston, MA
<br />11
<br />ill, IV
<br />115
<br />140
<br />28.8
<br />416
<br />-
<br />50.3
<br />90
<br />105
<br />28,2
<br />44,1
<br />1.02
<br />0.97
<br />1.14
<br />VA Beach, VA
<br />111, IV
<br />132
<br />37.9
<br />44.7
<br />114
<br />52.0
<br />0.73
<br />0.86
<br />Miami, FL
<br />1115 IV
<br />181
<br />71.3
<br />84,1
<br />146
<br />85.3
<br />0.84
<br />0.99
<br />Galveston, TX
<br />111, IV 1
<br />160
<br />55.7
<br />65.7
<br />132 1
<br />69.8
<br />0.80
<br />ON
<br />Dallas, TX
<br />111, IV 1
<br />120
<br />31.3
<br />-
<br />90 1
<br />32.4
<br />0.97
<br />-
<br />I Exposure Dat 33'mean roof height (for ASCE 7-10 only), K, = 1.18,
<br />2 Exposure C at 33'rnean roof height, K, = 1.0.
<br />ASCE 7-10 Wind Provisions 5 LinelCoulbourne
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