huangyhg

wind load force coeff., cf, for open bldg w/ gable roof
does anyone have a recommendation for determining the wind force coefficient, cf, for an open building with a gable roof? see asce7-98, section 6.5.13. this refers to tables 6-9 through 6-12 but i cannot find an applicable table. is there another procedure i should be using? thanks for your help.

in the british (cp3?) and south african (sabs0160) wind codes there is a cp for canopy roofs. if you give me the slope of the roof i can let you know the pressure coefficient. basically for a pitch of 15 degrees the maximum downward roof pressure coeff is cp=0.5 and the maximum upward pressure is cp=0.8. this varies depending on how much blockage you have under the roof from stacked contents. the maximum local pressure at the edges is cp=-1,9 (upwards).
carl bauer
it could be worth your while trying to download the draft revision of the australian/nz standard. (i have not verified that it is still downloadable - if not, my apologies).
refer to my posting (july 24, 2001) in thread 507-6585 "steel tower wind loading"
thank you for your response in eng-tips. the angle of the roof i mentioned
is actually pretty steep, 33.7 degrees. the ridge is 6 meters high and the
eave at 2.4 meters.
the tables actually only go up to a pitch of 20 degrees for a duopitch roof but for a monopitch they do go up to 30 degrees. you get some pretty serious uplift on a 30 deg monopitch and i would say these figures are conservative. the maximum downward pressure given for this case is cp=1.2 and the maximum upward is cp=-1.8. you need to multiply the free stream velocity pressure by these factors to get the pressure on your roof. this would be acting at right angles to the roof. the notes say that for a duopitch each slope should be able to support either max or min pressure and the whole canopy should be able to support one at max pressure and the other at min pressure.
your case is a little unusual and isn’t well covered by the codes. in these cases i usually look at it in a few different ways and take a view as to which is most representative. e.g. with such a steep slope you could just look at the whole thing as a vertical obstruction of height 3.6m with a 2.4m space under it. in fact this looks like it might yield the best model and is equivalent to a signboard which is covered in most codes.
carl bauer
be careful mixing cf values from different codes/sources. the coefficients sometimes are derived using different principles that cannot be used under different code structures.
paulking (visitor)15 sep 01 10:24
i am trying to determine wind forces on wire mesh or netting.. how it acts under high winds hurricane region.. if anybody could give me some guidance.. thanks

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