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Table 1. Comparison of design velocity pressures between ASCE 710 <br />Exposure C and ASCE 7-05 Exposure C <br />Location <br />Boston, MA <br />Risk <br />Category,(MPH) <br />11 <br />ASCE <br />7-10 <br />ASCU' 7-05 <br />Design <br />Wind <br />Speed <br />128 <br />ASD <br />Velocity <br />Pressure' <br />(SO <br />21 A <br />LRFD <br />Velocity <br />Pressure <br />(sl) <br />35.7 <br />Design <br />Wind <br />Speed <br />(MPH) <br />1.05 <br />ASD <br />Velocity <br />Pressure' <br />(st) <br />24.0 <br />LRFD <br />Velocity <br />Pressure' <br />(so <br />38.4 <br />VA Beach, VA <br />11 <br />122 <br />19.4 <br />32.4 <br />114 <br />28.3 <br />45.2 <br />Miami, FL <br />II <br />170 <br />37.7 <br />62.9 <br />146 <br />46.4 <br />74.2 <br />Galveston, TX <br />1i <br />150 <br />29.4 <br />49.0 <br />132 <br />37.9 <br />60.7 <br />Dallas, TX <br />Roston, MA <br />1] <br />III, IV <br />115 <br />140 <br />17.3 <br />25.6 <br />28.8 <br />42.6 <br />90 <br />105 <br />17.6 <br />27.6 <br />28.2 <br />44.1 <br />VA Beach, VA <br />111, IV <br />132 <br />22.7 <br />37.9 <br />11.4 <br />32.5 <br />52.0 <br />Miaini, FI:, <br />III, IV <br />181 <br />42.8 <br />71.3 <br />146 <br />53.3 <br />85.3 <br />Galveston, TX <br />III, IV <br />160 <br />33A <br />55.7 <br />132 <br />43.6 <br />69.8 <br />Dallas, TX <br />1II, IV <br />120 <br />18.8 <br />31.3 <br />90 <br />20.3 <br />32.4 <br />L"XPONU1-C k- UL .7,} 1tlCUtl 1-001 11C1V,11q, 1" z ® 1.V. <br />Exposure Category D <br />Table 2 provides the same information as Table 1 except ASCE 7-10 design velocity pressure is <br />calculated assuming Exposure D (e.g. sites where flat, unobstructed areas and water surfaces <br />prevail in the upwind direction). For an assumed 33' mean roof height, design pressures <br />calculated in accordance with ASCE 7-10 for Exposure D are 18% greater than those for <br />Exposure C. Design velocity pressures for ASCE 7-05 in Table 2 are based on Exposure C <br />because Exposure D is not applicable in hurricane prone regions per ASCE 7-05. <br />Effect of mean roof height is a factor in calculation of design velocity pressure. For the example <br />in this paper, all calculations are based on a mean roof height of 33' which corresponds to the <br />height limit of the JVFC . The value of the velocity pressure exposure coefficient, K,, for <br />Exposure C and 60' mean roof height is K, =1.13. For Exposure D and 60' mean roof height, the <br />value of K, = 1.31. The ratio of Exposure D to Exposure C at this height is 1.16 indicating <br />reduced influence of Exposure D as building height increases. <br />ASCE 7-10 Jf in Provisions 4 Line/Coutbo erne <br />