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Suinniai-y design velocity pressure conipai-ison between ASCE 7-10 and ASCE 705 <br />Table 3 compares the relative increase or decrease in design velocity pressures based on location, <br />building risk category, and exposure, <br />The inland location, Dallas, TX, shows only small differences between ASCE 7-10 and ASCE 7- <br />05. Locations outside of the hurricane prone region, not including special wind regions, can be <br />generally represented by a ratio of approximately 1.0 (see Table 3, column [A]/[C]) as shown for <br />Dallas, T.X. <br />An expected outcome, due to the uniform hazard basis of the new maps, is that design pressures <br />for Exposure C locations in the hurricane prone region are smaller under ASCE 7-10 than ASCE <br />7-05 (i.e. ratio values are less than 1.0 in'rable 3, column [A]/[C]), <br />In this example, the effect of new maps and applicability of Exposure D in hurricane prone <br />regions relative to Exposure C in ASCE 7-05 varies by location (see Table 3, column [B]/[C]). <br />An approximate 10 percent increase in design pressure is observed for Boston, MA and an <br />approximate 16 percent decrease in design pressure is observed for Virginia Beach, VA, <br />MINIMUM DESIGN WIND LOADS <br />Minil-nUrn wind load provisions of ASCE 7-10 for design of main wind force resisting systems <br />(MWFRS) under the directional procedure and envelop procedure, have also been revised to <br />specify a minimum 16 psf wall pressure and a minimum roof pressure of 8 psf projected onto a <br />vertical plane (see Figure 1). For comparison, the minimum design value of 10 psf, applicable for <br />both walls and roofs under ASCE 7-05, when factored for LRFD is 16 psf (i.e. 10 psf x 1.6 = 16 <br />psf) which identically matches the LRFD pressure of 16 psf for walls under ASCE 7-10, <br />Under ASCE 7-05 and prior editions, the net force for some elements of the MWFRS were <br />smaller than would result from minimum pressure requirements. Tile minimum LRFD pressures <br />of 8 psf for roofs and 16 psf for walls in ASCE 7-10 are now less likely to be the controlling <br />llnininlUrn design wind loads for sorne building configurations, particularly in lower wind speed <br />regions and for low-rise buildings designed in accordance with the envelop procedure for low- <br />rise buildings. <br />Figure 1. Application of minimum wind load. <br />ASCE 7-10 WindPt�ovisions 6 LinelCoulbozu-ne <br />